Law-making and Incommensurability
Henry S. Mather
The author explores the implications of incom-
mensurability for lawmakers. In a pluralistic society,
the task of preferring one objective over another in
cases where the value of these objectives cannot be
measured or compared is daunting. The author argues
that far from preventing rational choice, thoughtful
consideration of the concept of incommensurability
permits many legislative choices and precludes only
dogmatism and undue righteousness.
The author first defines the paramaters of the no-
tion of incommensurability, allowing for a deeper un-
derstanding of the concept and limiting the notion to
one that is relevant in the realm of practical decision
making. He discusses incommensurability in relation to
abstract notions of human goods, concrete instances of
these goods, and moral principles and virtues. He then
examines the ways in which decisions preferring the
realization of one incommensurable benefit over an-
other can be made in a manner that is not irrational.
The author concludes by challenging various ar-
guments that incommensurability either requires or
precludes certain doctrinal values or outcomes. He pro-
poses that consequentialism, liberalism, and absolute
rights and duties may be consistent with incommen-
surability, although not required by it. While philo-
sophical reflection on incommensurability will not lead
directly to answers, it offers an important contribution
to honest and reflective decision making.
L’auteur explore les implications que pose le pro-
blame de l’incommensurabilit6 pour les juristes. Dans
une soci&6t pluraliste, choisir une approche au lieu
d’une autre, particulirement lorsque ]a valeur de cette
approche ne peut etre mesure o compar6e, peut 6tre
un processus insatisfaisant. L’auteur propose une ana-
lyse du concept d’incommensurabilitl qui, plut6t que
d’empacher de faire un choix rationnel, pernet de faire
des choix 16gislatifs et pr6vient le dogmatisme et ]a
rectitude excessive.
L’auteur d~finit d’abord les param~tres de ]a no-
tion d’incommensurabilit6, permettant une meilleur
compr6hension du concept et limitant la notion A la
sphere pratique de prise de d6cision. II traite le concept
d’incommensurabilit6 d’abord par rapport a la notion
abstraite d’humanit6, en s’attardant sur quelques exem-
ples concrets, ensuite par rapport A certains principes
moraux et h la vertu. I1 examine finalement comment
des dacisions pr6f6rant la ralisation d’un ben6fice in-
commensurable au lieu d’un autre peuvent Etre prises
de mani~re rationnelle.
Pour conclure, l’auteur remet en question certains
arguments qui indiquent que l’incommensurabilitd re-
quiert o prdvient certaines valeurs o cons&luences
doctrinales. II propose de r~concilier les concepts de
cons~quentialisme, de libdralisme et de droits et de de-
voirs absolus avec ]a notion d’incommensurabilit6, bien
qu’ils n’en soient pas une condition n6ecessaire. Alors
qu’une
le concept
d’incommensurabilit6 n’apportent pas de r6ponses pr6-
cises, elie permet de prendre des decisions honn~tes et
rnflchies.
r6flexion philosophique
sur
“Distinguished Professor Emeritus of Law, University of South Carolina, School of Law.
McGill Law Journal 2002
Revue de droit de McGill 2002
To be cited as: (2002) 47 McGill L.L 345
Mode de r6fdrence: (2002) 47 R.D. McGill 345
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Introduction
1. Analysis of the Concept of Incommensurability
A. Defining “Incommensurability”
1. Metrical Commensurability
2. Ordinal Commensurability
3. Real versus Rational Incommensurability
B. The Domains of Incommensurability
1. Basic Human Goods
2.
3. Moral Principles and Moral Virtues
Instantiations of Basic Human Goods
C. The Extent of Incommensurability
II. How Lawmakers Can Resolve Conflicts between Incommensurable
Goods
A. Choice Permitted by Reason
B. Rational Choice and Arational Choice
C. Moral Principles
D. Social Traditions
E Prudential Principles
F
Intuition
II1. The Jurisprudential Implications of Incommensurability
A. Arguments against Consequentialism
B. Arguments for Liberalism
1. Individual Liberty
2. Diversity
3. State Neutrality
4. Free Markets
C. Arguments against Liberalism
D. Arguments against Absolute Rights and Duties
E. Arguments for Absolute Rights and Duties
Conclusion
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
Introduction
In recent years, moral, political, and legal philosophers have directed much of
their attention to the problem of value incommensurability.’ An acknowledgment of
incommensurability usually comes on the heels of value pluralism, the theory that
there are many morally relevant values, each of which is ultimate or basic in the sense
that it cannot be reduced to some other value, and each of which is worthy of our pur-
suit or allegiance.2 These values are diverse and often come into conflict with each
other when we must choose between alternative courses of action? This diversity of
values is also apt to result in frequent incommensurability, or the absence of a deter-
minate comparative ranking. If two conflicting values are completely diverse, so that
they have nothing in common and cannot both be reduced to the same more basic
value, it will be difficult to find a way to compare them and conclude that one is supe-
rior to the other.’ When one chooses one of the values over the other,
[w]hat one loses is of a different kind from what one gains. … [Q]uite com-
monly there is no meaning to the judgment that one gains more than one
loses…. When one was faced with valuable options … one simply chose one
way of life rather than another, both being good and not susceptible to com-
parison of degree.5
Although the plurality, irreducibility, and diversity of values does not necessarily en-
tail incommensurability,” it is easy to see why pluralists typically assert that conflict-
ing values are often incommensurable.
‘ See e.g. R. Chang, ed., Incommensurability, Incomparability, and Practical Reason (Cambridge,
Mass.: Harvard University Press, 1997); Symposium, “Law and Incommensurability” (1998) 146 U.
Pa. L. Rev. 1169.
2 See e.g. L Berlin, The Crooked imber of Humanity: Chapters in the History of Ideas (London:
John Murray, 1990) at 11, 79-80 [hereinafter Berlin, Crooked imber]; J. Raz, Ethics in the Public
Domain: Essays in the Morality of Law and Politics (Oxford: Clarendon Press, 1994) at 179 [herein-
after Raz, Ethics]. See also S. Wolf, “Two Levels of Pluralism” (1992) 102 Ethics 785 at 785.
See e.g. . Berlin, Four Essays on Liberty (London: Oxford University Press, 1969) at li, 169
[hereinafter Berlin, Four Essays]; S. Hampshire, Morality and Conflict (Cambridge, Mass.: Harvard
University Press, 1983) at 21, 155, 165.
4 Even if the two conflicting values have something in common and are thus only partially diverse,
any comparison in terms of whatever they have in common will still ignore the morally relevant fea-
tures that are unique to either value and will thus provide an inadequate ground for preferring one
value to the other.
3Raz, Ethics, supra note 2 at 179.
6 The lack of a common standard or measure does not logically preclude the possibility that one
value is superior to the other in some other way. See W. Sinnott-Annstrong, Moral Dilemmas (Ox-
ford: Basil Blackwell, 1988) at 59-60 (arguing that irreducibility does not entail incomparability:
whereas two moral requirements, such as, for example, (i) to not break a trivial promise, and (ii) to
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This article will focus on incommensurability as a problem in law-making, a par-
ticular form of practical choice involving the activity of adopting legal rules. In Part I,
we will analyze the concept of incommensurability. Incommensurability will be de-
fined as the absence of rational commensurability, either metrical or ordinal. We will
conclude that this incommensurability is often present in the domain of basic human
goods and in the domain of instantiations of basic human goods. Part II will demon-
strate that there are a number of resources that enable lawmakers to resolve conflicts
between incommensurable goods or instantiations without being irrational or even
arational. Each such resolution, however, is neither required by reason nor prohibited
by reason. In Part Im, this indeterminacy will lead us to reject a number of arguments
claiming that incommensurability implies a particular jurisprudential position on a
given substantive moral issue.
I. Analysis of the Concept of Incommensurability
When lawmakers choose among alternative legal rules, they are guided by certain
values relevant to moral choice. These values include the human goods that serve as
ends or goals of law-making (goods such as health, liberty, and employment in
meaningful work), and may also include moral principles or moral virtues. Typically,
these values come into conflict when lawmakers assess their rulemaking options. If
the conflicting values are incommensurable, the law-making options are apt to be in-
commensurable. In section A, below, a definition of incommensurability that can be
applied to alternative options or to conflicting values of any type will be developed.
We will use the generic word “items” to refer to any two or more things that lawmak-
ers may be trying to compare in order to make a choice.
A. Defining “Incommensurability”
Joseph Raz has suggested that items A and B are incommensurable (or “incom-
mensurate” or “incomparable”) if it is not true that A is better than B, not true that B
is better than A, and not true that A and B are of equal value.7 Ruth Chang, however,
claims that there is a fourth possible relation between A and B that can prevent in-
commensurability, namely, that A and B are “on a par” (meaning not precisely equal,
not kill, may not be reducible to a common standard, nevertheless they may be compared-(ii) is
clearly stronger than (i)).
‘ See J. Raz, The Morality of Freedom (Oxford: Clarendon Press, 1986) at 322-24 [hereinafter Raz,
Morality] (discussing the incommensurability of options). See also R. Warner, “Does Incommensura-
bility Matter? Incommensurability and Public Policy” (1998) 146 U. Pa. L. Rev. 1287 at 1287 (dis-
cussing the incommensurability of reasons for choice).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
but very nearly equal or roughly equal).’ Law-making is not a precise science, and
thus for law-making purposes, ascertaining that A and B are roughly equal usually
has the same significance as ascertaining that A and B are precisely equal, namely,
that a choice of either alternative is acceptable. We can thus approve the notion that
items are not incommensurable if they are roughly equal.
When is A not better than B, not worse than B, not precisely equal to B, and not
roughly equal to B? For the sake of convenience, we shall ask what it would take for
A to be better than B or worse than B or in a relationship of precise or rough equality
with B. If none of these comparative relationships obtain, we can say that the items A
and B are incommensurable. In other words, we shall inquire as to what makes items
commensurable and then say that incommensurability is the absence of any such
commensurability.
1. Metrical Commensurability
If both items A and B can be measured and assessed on a quantitative metric or
scale divided into units and using cardinal numbers, A and B are commensurable if
certain conditions are met.’ If a tape measure reveals that John is six feet one inch in
height and that Jim is five feet nine inches in height, John is superior to Jim with re-
spect to height. John’s height and Jim’s height have what we will call “metrical com-
mensurability”.
One condition for metrical commensurability is that the metric being used is an
appropriate metric that does not ignore any difference between the two items that is
relevant to the purpose of the comparison.9 The tape measure meets this condition be-
cause it measures height, and John and Jim are being compared only with respect to
height. The tape measure does not measure weight or intelligence, but differences in
weight or intelligence are not relevant here.
A second condition for metrical commensurability is that the metric being used be
capable of measuring all the items to be compared. When we compare John and Jim
in terms of height, the tape measure satisfies this condition because it can measure
‘ See R. Chang, “Introduction” in Chang, supra note 1, at 4-5, 24-27 (suggesting that items are
“comparable” and not “incomparable” with respect to some covering value if they are on a par). See
also J. Griffin, “Incommensurability: What’s the Problem?” in ibid 35 at 35, 38-39 (suggesting that
roughly equal forms of life are comparable).
9 See e.g. . Schauer, “Commensurability and Its Constitutional Consequences” (1994) 45 Hastings
LJ. 785 at 785 (indicating that values are commensurable if there is a way of reducing them to a sin-
gle metric).
‘0 See e.g. J. Finnis, “Commensuration and Public Reason” in Chang, supra note 1, 215 at 218-19
[hereinafter Finnis, “Commensuration”] (suggesting that goods and bads are not commensurable if
non-measurable differences are significant).
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both John’s height and Jim’s height. If there is no single metric that can measure both
items, the items are not metrically commensurable.”
If we are trying to compare two items in terms of an overall characteristic that de-
pends on multiple criteria, and each criterion requires a different metric, there may be
no one metric that measures everything that must be measured. However, the presence
of multiple criteria does not necessarily preclude satisfaction of the second condition
for metrical commensurability. Suppose we are comparing items A and B with respect
to overall competence and have correctly decided that overall competence depends on
two contributory criteria, with criterion 1 having twice as much weight as criterion 2.
Assume that each criterion has its own metric and there is no single metric that meas-
ures both criteria. Nevertheless, A is superior to B in overall competence if A has a
higher rating than B on the metric that measures criterion 1 and also has a higher
score than B on the metric that measures criterion 2. We have a complex metric that
measures both A and B in terms of overall competence and satisfies the second con-
dition. This complex metric consists of (1) a metric for measuring A and B in terms of
criterion 1, (2) a different metric for measuring A and B in terms of criterion 2, and
(3) an axiom that one item is overall better than the other if it is superior with respect
to both criteria.
Even if A is not better than B on both criteria, A is still superior in overall com-
petence if A has a score of 70 on criterion 1 and a score of 50 on criterion 2, while B
has a score of 60 on criterion 1 and a score of 60 on criterion 2. Because we have a
2:1 ratio that determines the relative weight of criterion 1 and criterion 2, and each
criterion has a metric that measures both A and B, we have a complex metric that
measures both A and B with respect to overall competence. The second condition for
metrical commensurability is satisfied.
A third necessary condition for metrical commensurability is the acceptance of
some axiom that enables measurement along a metric to yield a comparative judg-
ment without any intervening judgment other than a mechanical application of the
axiom. Typically, the axiom will be the familiar one: more units is better than fewer
units. This maximization notion is used in grading certain student exams (where A
must have a higher numerical score-more correct answers-than B in order to re-
ceive a higher letter grade) and in certain sports (where the team with the most points
is declared the winner). Other axioms are possible however. If what is most desired is
not maximization, but a mean between deficiency and excess, the axiom will indicate
that a measured score closer to that mean is better than a score further from that mean.
” See J. Finnis, Fundamentals of Ethics (Washington, D.C.: Georgetown University Press, 1983) at
87 [hereinafter Finnis, Ethics] (pointing out that the size of a page, the weight of a book, and the
number six are not commensurable; even though each has a quantitative measure, they lack a com-
mon measure).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
Thus, an item that is measured to be two units short of the mean is better than an item
measured to be five units beyond the mean. To satisfy the third condition for metrical
commensurability, all we need is some axiom that allows us to make a comparative
judgment about items by measuring units and applying the axiom, without any other
preliminary judgment.
A number of writers define incommensurability as the absence of what I am
calling metrical commensurability.’2 If metrical commensurability is not the only pos-
sible form of commensurability, such writers must come up with some term other
than “incommensurability” (“incomparability”, for example) to designate situations in
which items are not metrically commensurable or commensurable in any other way. It
seems preferable to use “incommensurability” to mean the absence of commensura-
bility in any form, and use different terms (such as “metrical commensurability”) to
designate different forms of commensurability.
2. Ordinal Commensurability
Even if the items to be compared cannot appropriately be quantitatively measured
by a metric using cardinal numbers, and thus lack metrical commensurability, they
might properly be ranked ordinally, in priority order, and thus have what we will call
“ordinal commensurability”.
For example, we may be playing a game of cards in which spades always trump
diamonds, so that a three of spades beats a nine of diamonds. Or we may have a sys-
tem of constitutional law in which the right to free speech always takes priority over
the goal of economic growth. These are examples of situations in which there is a
fixed, absolute hierarchy between two or more classes of items, so that an item be-
2 See e.g. R. Craswell, “Incommensurability, Welfare Economics, and the Law” (1998) 146 U. Pa.
L. Rev. 1419 at 1421 (two options are incommensurable if there is no scale or metric that would rank
the options and justify choosing the higher-ranking option); E.A. Posner, ‘The Strategic Basis of
Principled Behavior: A Critique of the Incommensurability Thesis” (1998) 146 U. Pa. L. Rev. 1185 at
1185 (the incommensurability thesis holds that we cannot always value options along a common and
normatively justified metric); F Schauer, “Instrumental Commensurability” (1998) 146 U. Pa. L. Rev.
1215 at 1215-16 (those who argue for commensurability maintain that “all values, reasons, options, or
norms can be compared to each other even if they cannot be reduced to a common metric”); T.K
Seung & D. Bonevac, “Plural Values and Indeterminate Rankings” (1992) 102 Ethics 799 at 799, n. 1
(“incommensurable” means the unavailability of a common scale for measuring two or more things
we want to compare or rank); C.R. Sunstein, “Incommensurability and Valuation in Law” (1994) 92
Mich. L. Rev. 779 at 780,796 (human goods are incommensurable if they cannot be assessed along a
single purely quantitative “metric without doing violence to our considered judgments about how
these goods are best characterized”).
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longing to a higher-ranking class is always superior to an item that is a member of a
lower-ranking class. 3
We should note that even if the items to be compared belong to classes that are ar-
ranged in absolute hierarchical order, this does not guarantee ordinal commensurabil-
ity. Assume that class A is always superior to class B and always superior to class C,
and that class B is always superior to class C. If we are trying to compare an item be-
longing to class A with a combination of two items, one of which belongs to class B
and one to class C, our hierarchy of classes does not yield a determinate comparison;
it does not dictate that an A is superior to a combination of a B and a C.” Although B
is inferior to A, and C is inferior to A, the combined strength of B and C might match
or exceed the strength of A. Another situation in which a fixed hierarchy among
1 It is sometimes claimed that incommensurability is present if items of class A should never be ex-
changed with or traded off for items of class B. See Raz, Morality, supra note 7 at 345-57 (suggesting
that a value such as parenthood or friendship has “constitutive incommensurability” with money be-
cause refusing to exchange such a value for money is a constitutive aspect of the value; we cannot
even compare parenthood or friendship with money, for to do so would make the relationship of par-
enthood or friendship impossible); Warner, supra note 7 at 1291-1303 (arguing that constitutive in-
commensurability exists when certain commitments exclude certain options or reasons from even
being considered, from even being compared with the options or reasons to which one is committed).
Other writers, however, have suggested that this so-called constitutive incommensurability is ac-
tually ordinal commensurability. If items of class A must never be sacrificed in order to obtain items
of class B, this must be because A is ordinally superior to B in a fixed hierarchy. See Chang, supra
note 8 at 19-21; L. Alexander, “Banishing the Bogey of Incommensurability” (1998) 146 U. Pa. L.
Rev. 1641 at 1647.
Raz maintains that refusing to sacrifice friendship for money is not based on a judgment that
friendship is ordinally superior to money: if friendship were always superior to money, it would be
wrong for a person to pass up an opportunity to buy friendship with money (a conclusion that should
be rejected because it is incompatible with the view that friendship must be neither sold nor bought).
See Raz, Morality, supra note 7 at 352. But the ordinal superiority of friendship over money would
not entail that it is wrong to pass up an opportunity to purchase a (specious) friendship with money.
We could consistently say that true friendship is always superior to money and that one should not
attempt to sell or buy friendship because it cannot be done and because widespread attempts to do it
would impair friendship as a social good.
We should distinguish between two different kinds of norms prohibiting trade-offs. A norm pro-
viding that A should never be sacrificed in order to obtain B but that B may be sacrificed in order to
obtain A certainly reflects an ordinal ranking in which A is superior to B. A norm providing that A
and B should not be traded in free market exchanges need not reflect any ordinal ranking of A and B.
But neither does it necessarily reflect or create incommensurability. There may be a good reason to
believe that A is always superior to B but that A and B should not be exchanged in free markets.
14 See Sinnott-Armstrong, supra note 6 at 68-69 (noting that the ordinal ranking of moral require-
ments does not achieve comparability if one requirement supports one action option while two lower-
ranking requirements support an incompatible option).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
353
classes does not yield a determinate comparison is that involving a conflict between
two items belonging to the same class.
If the items to be compared do not belong to classes that are arranged in a fixed
hierarchy, ordinal commensurability might still be possible if the classes are ordered
in a variable hierarchy. We may, for example, have a rule providing that items in class
A outrank items in class B, except in circumstances x, y, or z, where items in class B
outrank items in class A.
Finally, ordinal commensurability may exist even in situations where the items to
be compared do not belong to classes that appear in any hierarchical ranking, either
fixed or variable. Here we would be comparing two items in their concrete particular-
ity. It may be difficult to imagine how it could be true that one item is ordinally supe-
rior to the other if we have no rule creating an ordinal hierarchy between the classes to
which the items belong.’5 Nevertheless, there may be truths that do not depend on hu-
man-made rules, and some of these truths may relate to concrete particulars. We will
consider such possibilities in the next subsection. As suggested in section B.2 below,
there may also be rules made by humans requiring a judgment that two items be-
longing to the same class are ordinally commensurable, even though they are not met-
rically commensurable. For now, let us merely recognize the theoretical possibility
that concrete, particular items can have ordinal commensurability without being
members of ranked classes.
The conception of ordinal commensurability presented above would seem to be
so broad that it can account for any commensurability that is not metrical commen-
surability. Based on the analysis so far, we can then say that incommensurability is a
breakdown in ranking,” the absence of both metrical commensurability and ordinal
commensurability, so that it is not true that one item is superior to the other(s) and not
true that the items are precisely, or even roughly, equal. This formulation cannot serve
as our final definition of incommensurability, however, because of a critical ambiguity
concerning the word “true”.
3. Real versus Rational Incommensurability
Law-making involves moral judgments, and the items that lawmakers try to com-
pare are often moral values (human goods, moral principles, or moral virtues). If
someone makes a statement in the form, “It is true that moral value A is superior to
moral value B,” what kind of truth is being claimed? In the realm of moral discourse,
” Note that all of my previous examples of ordinal commensurability involve some rule or rule-like
6 See Griffin, supra note 8 at 35-36 (suggesting that the most serious threat to practical rationality
notion that applies directly to classes of items and only indirectly to particular items.
comes from a breakdown in ranking).
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the word “true” is apt to be ambiguous. It might mean that the moral proposition has
real truth, or it might mean that the proposition has rational truth.
I am using “real moral truth” or “real truth” to refer to the kind of truth acknowl-
edged by moral realists. Moral realism is the theory that at least some moral proposi-
tions or judgments are true in virtue of a moral reality that is part of the world in
which we live but is independent of human beliefs, reasoning, or awareness concern-
ing the moral issue to which the proposition or judgment is addressed.” Real truth is
true because of an independent reality, even if we humans deny its truth or fail to per-
ceive it when we fully utilize our rational capacities. Such truth may be too deep
down in the fabric of the universe for us to apprehend it.
” For similar definitions of moral realism, see D. McNaughton, Moral Vision: An Introduction to
Ethics (Oxford: Basil Blackwell, 1988) at 7, stating that moral realism “insists that there is a moral re-
ality which is independent of our moral beliefs and which determines whether or not they are true or
false.” Moral properties are part of the “furniture of the world” and whether such a property is present
“does not depend on what we think about the matter”; Sinnott-Armstrong, supra note 6 at 191, sum-
marizing the definitions of David Wiggins, Mark Platts, and Thomas Nagel, which indicate that real
moral truth is independent of our moral beliefs and our ability to recognize such truth. See also P.
Foot, “Moral Realism and Moral Dilemma” in C.W. Gowans, ed., Moral Dilemmas (New York: Ox-
ford University Press, 1987) 250 at 268-69 (suggesting that a realist theory refuses “to let the posses-
sion of truth or falsity by a particular ethical proposition stand or fall by our capacity or lack of ca-
pacity for assigning truth or falsity to it”); C.W. Gowans, “Introduction” in Gowans, ibid. 3 at 30
(noting that in one sense of the term, moral realism is the view that the truth-value of a moral statement
or judgment is determined by a world that is independent of human reason, perception, or desire).
Although moral realism holds that real moral truth is independent of what we humans think
about the matter in question, I see no reason why a moral realist must also assert that real moral truth
is always independent of all human thoughts, attitudes, and feelings. Indeed, there would be no place
for morality (as we experience it) in a world devoid of human thoughts and feelings. Any real moral
truth relevant to human living must be a truth that is not totally independent of human nature, and our
thoughts and feelings are integral parts of our human nature.
Even if I am wrong about this, and any real moral truth is entirely independent of all human
mental states, this does not entail that all moral propositions or judgments have truth-conditions that
are entirely independent of such mental states. The moral judgment that I should not call Jane an idiot
might be derived from (1) a real moral truth that we should not hurt other peoples’ feelings, in con-
junction with (2) an empirical proposition that Jane’s feelings will be hurt if I call her an idiot. The de-
rived judgment has two truth conditions: premises (1) and (2) must be true in order for the derived
moral judgment to be true. But while the first premise might be a real moral truth independent of hu-
man mental states, the second premise is an empirical proposition whose truth depends on the actual
mental state of Jane. We thus cannot say that all moral propositions or judgments have truth-
conditions that are entirely independent of human mental states. Although real moral truths may serve
as our basic moral principles, our derived and more particular judgments will often require additional
premises that are not real moral truths-premises the truth of which is dependent on human mental
states.
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
355
One way we may interpret a statement that values A and B are truly incommensu-
rable is therefore to regard it as an assertion that there is nothing in independent real-
ity making it true that A is superior to B, that B is superior to A, or that A and B are
precisely or roughly equal in value.8 According to this interpretation, incommensura-
bility is not simply our inability to discern metrical or ordinal commensurability. It is
more radical than that. Incommensurability is “real incommensurability”, incommen-
surability as a matter of real moral truth.”
Alternatively, a statement about the commensurability or incommensurability of
values A and B might be interpreted as a statement claiming to have not real moral
truth, but rational moral truth. By “rational moral truth” (or “rational truth”), I mean
the kind of truth ascribed to moral propositions that are determinately true by virtue of
the generally accepted rules of rationality that govern practical reasoning-reasoning
employed in choosing among action options. Rational truth is determined by rules
constructed by humans to govern human thinking and is therefore constructive truth,
as distinguished from real truth.
Thus, a statement that values A and B are truly incommensurable might be inter-
preted as an assertion that the rules of rationality do not establish the truth of a propo-
sition that A is superior to B, or a proposition that B is superior to A, or a proposition
that A and B are precisely, or roughly, equal in value. Such “rational incommensura-
bility” is the failure of any assertion of metrical or ordinal commensurability to be
true under the generally accepted rules of rationality governing practical reason. Ra-
tional incommensurability results when no particular ranking of items is required by
rational reason. A number of writers seem to have this notion of rational incommen-
surability in mind when they discuss incommensurability.’
8 A slightly different interpretation would be an assertion that there actually is something in inde-
pendent reality making it false that A is superior to B, false that B is superior to A, and false that A
and B are precisely or roughly equal. But both interpretations yield assertions of real incommensura-
bility based on the nature of an independent moral reality, and we can ignore the logical distinction
between “not true” and ‘false”.
‘9 See J. Gray, Enlightenment’s Wake: Politics and Culture at the Close of the Modem Age (London:
Routledge, 1995) at 70 [hereinafter Gray, Enlightenment’s Wake] (suggesting that incommensurability
is not an imperfection in our understanding, but a feature of the world, and that the thesis of value in-
commensurability is a species of moral realism).
‘ See e.g. Raz, Morality, supra note 7 at 324, 333 (suggesting that when two options are incom-
mensurable, reason is indeterminate and has no judgment to make concerning their relative value);
R.P. George, ‘Does the ‘Incommensurability Thesis’ Imperil Common Sense Moral Judgments?”
(1992) 37 Am. J. Juris. 185 at 187, n. 9 [hereinafter George, “Moral Judgments”] (stating that the is-
sue between critics and defenders of the incommensurability thesis is whether basic values and their
instantiations are objectively commensurable by reason); L.A. Komhauser, “No Best Answer?”
(1998) 146 U. Pa. L. Rev. 1599 at 1604-05 (suggesting that two options are incommensurable, as in-
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Whether two or more values are rationally commensurable or rationally incom-
mensurable necessarily depends on what rational requirements are acknowledged.’
An assertion of commensurability does not have rational truth unless that assertion is
required by generally accepted rules of rationality.’ These rules are not as easy to
identify as one might think. The rules of rationality undoubtedly differ from one
realm of reason to another,’ and as Lewis Kornhauser notes, the criteria of rationality
in law-making even differ from one branch of government to another.’ Furthermore,
even within one discrete branch of law-making, it may be impossible to identify a set
of rules of rationality that is both sufficient for a decision and generally accepted by
lawmakers. In the absence of any such set of rules, no conclusion of commensurabil-
ity is required by reason.
There are a few rules of rationality that would be generally accepted in any realm
of reasoning. Reasoning must be reflective and deliberate. One must not disregard
known relevant facts. Conclusions must be based on premises or reasons. Reasoning
must not violate the rules of logic.
In realms of law-making, there may be some additional rules of rationality gov-
erning public policy. Kornhauser has identified two plausible rules of rationality gov-
erning lawmakers who seek to integrate values for the purpose of choosing among
alternative legal rules: (1) the rule of Pareto-superiority-if rule 1 serves each value
better than rule 2 does, choose rule 1; and (2) the rule of “nondictatorship”-the val-
ues to be served must not be ranked in absolute lexical order.’ As Kornhauser notes,
(1) the rule of Pareto-superiority does not apply when rule 1 serves value A better
than rule 2 does, but rule 2 serves value B better than rule 1 does, and (2) the nondic-
tatorship rule may not be generally accepted in some contexts.’ Kornhauser suggests
that even with these two rules rationality will generally leave more than one permissi-
struments promoting ends, when rationality does not determine any particular ranking of the options,
all values considered); E. Millgram, “Incommensurability and Practical Reasoning” in Chang, supra
note 1, 151 at 151 (indicating that worries about the incommensurability of ends arise when practical
reasoning seems to run out before determining a decision).
2 Komhauser, ibid. at 1608, 1619 (noting that whether options are instrumentally incommensurable
depends on the conditions that rationality imposes on the integration of ends).
22 An assertion of incommensurability, on the other hand, has rational truth, as a matter of default,
when no statement of commensurability (that A is superior to B, that B is superior to A, or that A and
B are precisely or roughly equal) is required by the rules of rational reason.
2′ See Finnis, “Commensuration”, supra note 10 at 219, 223 (suggesting that deliberation about
moral options is just one of four distinct domains of reasoning).
24 See Komhauser, supra note 20 at 1619.
Ibid. at 1608-11, 1617-18. I would state the Pareto rule somewhat differently: If rule 1 serves at
least one value better than rule 2 does and does not serve any value less well than rule 2 does, choose
rule 1.
26Ibid. at 1609-10 (concerning the Pareto rule), 1611 (concerning the nondictatorship rule).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
357
ble ordering of options,’ and it is difficult to cure this incommensurability by identi-
fying any additional rules required by rationality.’
Because of the distinction between real incommensurability and rational incom-
mensurability, a moral proposition can have one kind of truth without the other. There
are four possibilities. First, two or more values might be incommensurable as a matter
of real moral truth and also rationally incommensurable. Second, it is also possible
that the values are commensurable as a matter of real moral truth and rationally in-
commensurable, due to the inability of human reason to discern commensurability in
a moral reality that is independent of human reason. Third, it is even possible that the
values are incommensurable as a matter of real moral truth and rationally commensu-
rable, due to human-made rules of rational reasoning that require a conclusion that
certain values are commensurable when that conclusion is actually contrary to inde-
pendent moral reality. Fourth, the values might be commensurable as a matter of real
moral truth and also commensurable as a matter of rational truth.
Should we define incommensurability as real incommensurability or as rational
incommensurability? We sometimes know whether conflicting values are rationally
commensurable or incommensurable. For example, it is often obvious that the gov-
erning rules of rationality do not establish the truth of any statement asserting com-
mensurability, and that the values are therefore incommensurable. However, we will
almost never know whether conflicting values are really commensurable or incom-
mensurable. Independent moral reality is very mysterious; it seems to lie beyond the
reach of human epistemic capacities. Although a few mystics may be able to appre-
hend real moral truth by way of intuition or a leap of faith, they cannot support their
beliefs by the kind of epistemically reliable methods that yield knowledge.
The fact-if it is a fact-that the conflicting values are commensurable or in-
commensurable as a matter of real moral truth will have no effect on law-making if
lawmakers have no way of knowing that fact and are unwilling to act on the basis of
mystical speculation about the real moral truth of assertions of commensurability or
incommensurability. Although I believe (as a matter of faith) that there are some real
moral truths concerning the commensurability or incommensurability of values, I
propose that we define incommensurability as rational incommensurability, so that in-
commensurability can offer some practical implications for lawmakers who are not
mystics.’
=’Ibid at 1611.
‘ IbiaJ at 1618.
= A moral realist may object that the existence of real moral truth about incommensurability does
have important implications for law-making. Even if no one knows the real moral truth, it might be
apprehended by intuition, and lawmakers should therefore put important moral decisions into the
hands of those persons who are most likely to intuit the real moral truth concerning commensurability
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We can now define incommensurability with respect to the conflicting values
relevant to law-making. Two values are incommensurable if and only if generally ac-
cepted rules of rationality do not require, as a matter of either metrical or ordinal
commensurability, that any of the following propositions be regarded as true:
(1) value A is superior to value B; (2) value B is superior to value A; (3) A and B are
precisely equal in value; or (4) A and B are roughly equal in value.
B. The Domains of Incommensurability
We have confined the scope of our analysis to moral values that lawmakers con-
sider when they choose among alternative legal rules. Which kinds of moral values
are rationally incommensurable? Human goods? Moral principles? Moral virtues?
1. Basic Human Goods
A number of writers assert that basic human goods are incommensurable with
each other.’ “Human goods” are things that should be desired as ends and should
serve as reasons for action, because they are necessary, constituent aspects of human
well-being or flourishing.” “Basic” human goods are human goods that cannot be re-
and incommensurability (such persons may be lawmakers, or they may be private citizens). However,
I do not see any reliable way of identifying such persons.
” See Finnis, Ethics, supra note 11 at 94 (asserting that “[t]he basic human goods at stake in any
morally significant situation of choice are incommensurable”); J. Finnis, Natural Law and Natural
Rights (New York: Clarendon Press, 1980) at 112 [hereinafter Finnis, Natural Law] (asserting that the
basic aspects of human well-being are incommensurable); W.A. Galston, Justice and the Human
Good (Chicago: University of Chicago Press, 1980) at 94 (asserting that “[n]one of the basic goods
has absolute priority over any of the others” and that there is no common denominator by which they
can be quantitatively compared); R.P. George, Making Men Moral: Civil Liberties and Public Moral-
ity (New York: Clarendon Press, 1993) at 13 [hereinafter George, Making Men Moral] (asserting that
the basic human goods are many and incommensurable); G. Grisez, J. Boyle & J. Finnis, “Practical
Principles, Moral Truth, and Ultimate Ends” (1987) 32 Am. J. Juris. 99 at 110 (asserting that the basic
goods are incommensurable; no basic good as such can be meaningfully said to be better than an-
other).
“‘ See Finnis, Ethics, ibid. at 35-36 (suggesting that human goods are ends that can be intelligently
regarded as desirable), 50-51 (suggesting that the basic human goods are aspects of human well-
being, forms of human flourishing); Finnis, Natural Law, ibid. at 85 (suggesting that forms of good
are intelligently perceived as to-be-pursued), 64, 81, 87-88 (suggesting that human goods are aspects
of human well-being); George, Making Men Moral, ibid. at 12-13 (stating that “[t]he human goods
that provide basic reasons for action are fundamental aspects of human well-being and fulfillment”),
… [n]ot mere means
15 (stating that “[b]asic human goods are intrinsic and constitutive aspects of-
to-complete human well-being and fulfillment”); Grisez, Boyle & Finnis, ibid. at 106 (stating that
basic goods function as ultimate rational grounds for proposing actions).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
duced to some more fundamental good. 2
When we view basic human goods as abstract concepts designating generic
classes of items, it seems likely that all or most of them are rationally incommensura-
ble. Using knowledge as an example of a basic human good, we view knowledge as
an abstract good when we are concerned only with knowledge as such, without regard
to any particular instantiation or example of knowledge. If we try to compare knowl-
edge and friendship as abstract goods, we cannot compare them in terms of the meas-
urable quantity of goodness each has, because they are merely abstract concepts.
Trying to measure the quantity of goodness in an abstract concept of knowledge or
friendship would be as futile as trying to measure the amount of light in an abstract
concept of light, or the number of inches in an abstract concept of the human foot.
Metrical commensurability is therefore elusive when we try to compare basic human
goods as abstract goods, keeping in mind that if they are truly basic goods, they can-
not be reduced to some other good that might have an appropriate metric.
Could knowledge and friendship, viewed as abstract goods, be rationally com-
mensurable by virtue of some ordinal comparison? Perhaps one of these goods is
more good than the other, not in the sense of having a greater quantity of goodness,
but in the sense of always having a higher quality of goodness. Or perhaps, in this
same qualitative sense, the two goods must always be ranked as equal. It does not
seem, however, that we have any rules of rationality requiring us to rank knowledge
and friendship in any particular hierarchal order, either fixed or variable. It thus ap-
pears that abstract goods like knowledge and friendship lack ordinal commensurabil-
ity as well as metrical commensurability and are therefore rationally incommensura-
ble. In the domain of basic human goods, viewed as abstract goods, rational incom-
mensurability is undoubtedly widespread, if not ubiquitous.
2.
Instantiations of Basic Human Goods
Another question that arises is whether instantiations of basic human goods can
be rationally incommensurable. Here the items to be compared are not abstract basic
goods (knowledge as such, friendship as such), but concrete, empirical instances or
realizations of basic goods. Dr. Anderson’s knowledge of patient Smith’s medical
history would be an instantiation of the basic human good we call knowledge. Al-
though lawmakers are seldom forced to decide whether one abstract basic good is al-
ways more valuable than another, they must often choose between a law that will
32 See Finnis, Natural Law, ibid at 92 (stating that a basic form of good cannot be analytically re-
duced to being merely an aspect of another form of good); George, Making Men Moral, ibid at 13
(stating that basic human goods are irreducible); Grisez, Boyle & Fimnis, ibid at 110 (stating that basic
goods are primary principles; “if they were reducible to something prior, they would not be primary”).
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likely produce one set of instantiations of basic human goods, and an alternative law
that will probably yield a very different set of instantiations. Indeed, lawmakers are
usually choosing between alternative sets of instantiations of basic human goods
(typically, rather large sets involving many persons). Thus, if an incommensurability
thesis is to have widespread jurisprudential significance, it must assert incommen-
surability among instantiations.
It would seem that in some cases, two instantiations of the same basic good are
rationally commensurable. Empirical instantiations of one basic good may have at-
tributes that can be measured (for example, amount, duration, or purity). This might
permit metrical commensuration of two instantiations of the same basic good, so long
as the metric does not ignore some significant attribute and measures the degree to
which the basic good is actually realized in each instantiation.3 For example, rational-
ity may require the conclusion that Smith’s health now is better than it was a year ear-
lier, as measured in physiological tests. If so, these two instantiations of the basic
good of health are rationally commensurable.
If the extent to which a basic good is realized in instantiations cannot be meas-
ured, two instantiations of that good may still have ordinal commensurability. We can
often distinguish between an instantiation that increases the realization of a good and
an instantiation that decreases the realization of that good, even though we cannot
measure the extent of the increase or decrease. Assuming that all other things are
equal, rationality may require that increasing the depth of my friendship with the An-
dersons be preferred to the atrophy of that friendship. As well, even though some or
all aspects of a basic good are not measurable, rationality may require the judgment
that one instantiation of that good is inferior to another instantiation of that same good
if the latter instantiation is exactly like the former instantiation in every aspect except
for one aspect that only the second instantiation provides. I may, for example, be
choosing between two equally priced recreational fishing trips, both of which involve
the same waters at the same time with equivalent equipment, but only one of which
provides an experienced guide.
As the unusual nature of the preceding examples indicates, there are many cases
in which two instantiations of the same basic human good are rationally incommensu-
rable?’ Frequently, the extent to which that good is realized in alternative instantia-
“‘ What may appear to be a measure of the extent to which a basic good is realized is often only a
measure of a means to such realization. Four years of university education is a measure of a means of
realizing the basic good of knowledge, but it is not a measure of the knowledge a student has acquired.
34See George, “Moral Judgments”, supra note 20 at 189 (stating that alternative instantiations of the
same basic value are often incommensurable); Grisez, Boyle & Finnis, supra note 30 at 110 (indicat-
ing that instantiations of the same basic good are incommensurable when each alternative instantia-
tion offers some appealing aspect that the other instantiation does not).
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tions cannot be measured, and rationality does not require any particular ordinal
ranking of the instantiations. How, for example, could rationality dictate any particular
ranking of two instantiations of the basic good of aesthetic experience, when one in-
stantiation comes from attending a Metropolitan Opera production of Rossini’s La
Cenerentola, and the other instantiation is brought about by attending a Met produc-
tion of Verdi’s La Traviata?
Instantiations of different and incommensurable basic human goods will usually
be rationally incommensurable.’ As instantiations of diverse basic goods, they are
unlikely to have a common measure. As instantiations of basic goods that are not or-
dinally ranked, they cannot themselves be ranked on the basis of their membership in
ranked classes. Nevertheless, there may be situations in which rationality requires
some particular ranking between instantiations of different basic goods. For example,
it may be unreasonable to deny that an instantiation of good A should be preferred to
an instantiation of good B in a situation where there is a dire need for A and B is al-
ready realized to the extent necessary for a good life.’
We must conclude that instantiations of basic human goods are often rationally
incommensurable. Instantiations of the same basic good are sometimes rationally
commensurable and sometimes rationally incommensurable. Instantiations of differ-
ent basic goods are usually rationally incommensurable, but might be rationally
commensurable in certain situations.
3. Moral Principles and Moral Virtues
Moral principles often conflict and may be rationally incommensurable 7 It is un-
likely that all moral principles can be ranked in one fixed order. However, there may
” See G. Grisez, “Against Consequentialism” (1978) 23 Am. J. Juris. 21 at 39 (stating that in
choosing between “participations” of two different and incommensurable goods, the “greatest net
good” is meaningless); Grisez, Boyle & Finnis, ibid (stating that incommensurability obtains “even”
between instantiations of the same basic good, and thus implying that incommensurability obtains
between instantiations of different basic goods).
“‘ Compare J. Kekes, The Morality of Pluralism (Princeton: Princeton University Press, 1993) at 50
[hereinafter Kekes, Pluralism] (suggesting that a claim for religious fasting (a particular form of the
secondary good of religious observance) can defeat a claim for bread (a particular form of the primary
good of nutrition) if minimum requirements for nutrition are akeady generally satisfied).
“‘ See J. Gray, Isaiah Berlin (Princeton: Princeton University Press, 1996) at 146-49 [hereinafter
Gray, Berlin] (summarizing Berlin as holding that conflicts between deontic principles of justice are
sometimes not rationally arbitrable); Hampshire, supra note 3 at 116-18 (suggesting that conflicts
between moral principles sometimes result in a breakdown of clear reasoning); McNaughton, supra
note 17 at 196 (arguing that it is “implausible to suppose that our moral principles can be ranked in an
invariable order”); Sinnott-Armstrong, supra note 6 at 96-97 (suggesting that moral principles cannot
all be ranked in a fixed, absolute order because some principles will cover both important and trivial
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be other ways to make conflicting moral principles ordinally commensurable (metri-
cal commensurability would seem to be out of the question). Much depends, of
course, on the structure of our deontic system of moral principles. In a complete
deontic system, all conflicts between principles could be resolved by one or more
master principles. 8 But our lawmakers use moral principles that serve diverse ends
and purposes, and it is unlikely that they will recognize, as rationally compelling, any
deontic system involving master principles that resolve, authoritatively and a priori,
all conflicts between moral principles.
Moral virtues such as justice and mercy can come into conflict that cannot be re-
solved by rational analysis. In such cases, virtues are rationally incommensurable.”
Basic human goods are often rationally incommensurable with each other, moral
principles are often rationally incommensurable with each other, and moral virtues are
often rationally incommensurable with each other. It is therefore not surprising that
values in one domain will often be rationally incommensurable with values in another
domain. Basic goods will be incommensurable with moral principles; moral princi-
ples will be incommensurable with moral virtues; moral virtues will be incommensu-
rable with basic goods.
C. The Extent of Incommensurability
It thus appears that we live in a world replete with moral conflict and the rational
incommensurability of conflicting moral values. In the remainder of this article, we
will inquire how conflicts between rationally incommensurable values might be re-
solved and will consider some possible jurisprudential implications of value incom-
mensurability. In the interests of brevity and simplicity, we will focus on incommen-
surability between basic human goods or between instantiations of basic human
goods.
instances, and an important instance of one principle must be ranked above a trivial instance of an-
other principle, and vice versa. However, any such ranking of particular instances is merely intuitive);
Griffin, supra note 8 at 51 (stating that we will likely encounter incomparable (incommensurable)
moral norms from time to time).
” Such a master principle need not involve a fixed hierarchy for all subordinate principles. It might
provide that in all private law disputes, the moral principle that best promotes individual responsibility
will have priority, whereas in all public law disputes, the moral principle that best promotes domestic
tranquility will have priority. We might be able to imagine some such master principle (or set of mas-
ter principles) that would resolve all conflicts among moral principles, though I doubt that we would
like what we had imagined.
” See Hampshire, supra note 3 at 116-18 (suggesting that conflicts between virtues, like conflicts
between moral principles, sometimes result in a breakdown of clear reasoning).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
363
First we must clarify the incommensurability thesis with respect to the extent of
incommensurability being asserted. For abstract basic human goods, there would
seem to be three possibilities:
(al) All abstract goods are commensurable with each other;
(a2) Some pairs of abstract goods are commensurable, and other pairs of abstract
goods are incommensurable;
(a3) All abstract goods are incommensurable with each other.
Similarly, with respect to instantiations of abstract basic human goods, there seem to
be three possibilities:
(il) Instantiations are always commensurable with each other;
(i2) Some pairs of instantiations are commensurable, and other pairs of instan-
tiations are incommensurable;
Instantiations are always incommensurable with each other.
(i3)
Our preceding analysis should lead us to reject (al) and (il). In the realm of ra-
tional rather than real commensurability, it seems clear that some abstract goods are
incommensurable with each other and that some instantiations are incommensurable
with each other. We have seen also that some pairs of instantiations are commensura-
ble and should thus reject (i3). The proposition in (a3) will be controversial. Some of
us will accept it,’ while others will maintain that human life has an absolute ordinal
priority over other (or at least some other) basic human goods and is rationally com-
mensurable with them as abstract concepts.”
In order to present the incommensurability thesis in its more moderate form, we
will assume that it asserts (a2) and (i2). Confining our thesis to basic human goods
and their instantiations, and interpreting incommensurability as rational incommen-
surability, we get the following incommensurability thesis: with respect to some pairs
of basic human goods and some pairs of sets of instantiations of basic human goods,
A and B are incommensurable in the sense that generally accepted rules of rationality
do not require, as a matter of either metrical or ordinal comparison, that any of the
following propositions be regarded as true: (1) A is superior to B; (2) B is superior to
A; (3) A and B are precisely equal in value; or (4) A and B are roughly equal in value.
4′ See e.g. Finnis, Natural Law, supra note 30 at 92-93 (arguing that there is no objective hierarchy
among the basic goods, not even a priority for life as such); Kekes, Pluralism, supra note 36 at 122-23
(arguing that life does not always override other values; if we believed it did, we would lower the
speed limit for motorists and outlaw parachute jumping and Himalayan expeditions).
41 See e.g. Grisez, supra note 35 at 50 (stating that life is a greater good than health).
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I suspect that whatever the generally accepted rules of rationality are, this incom-
mensurability thesis is sound. Our next task is to consider some possible implications
of this thesis. In Part II, we will ask whether incommensurability precludes rational
choice in law-making. In Part Hll, we will consider a number of arguments claiming
that incommensurability implies a particular position on a given substantive jurispru-
dential issue.
II. How Lawmakers Can Resolve Conflicts between Incommensurable
Goods
Suppose that a body of lawmakers has ascertained that A is a basic human good
that would be promoted by the implementation of legal rule X. The lawmakers thus
have teleological reasons for adopting rule X. The lawmakers have also ascertained
that B is a basic human good that can be promoted by the implementation of legal rule
Y. The lawmakers thus have teleological reasons for adopting rule Y. Suppose further
that X and Y are contrary and incompatible legal rules dealing with the same issue;
the lawmakers must choose between rule X and rule Y and must thus choose between
promoting good A and promoting good B in this area of the law. Suppose, finally, that
the lawmakers have considered all relevant rules of rationality and have correctly per-
ceived that the foreseeable instantiations of good A produced by rule X are rationally
incommensurable with the foreseeable instantiations of good B produced by rule Y;
the rules of rationality do not require that the lawmakers prefer good A over good B
and do not require a preference for B over A. Does this mean that either preference
(adoption of either rule X or rule Y) would be irrational? Not at all.
A. Choice Permitted by Reason
A choice to promote one good over another conflicting good will merit one of
three possible judgments concerning the rational status of that choice: (1) the choice
was required by reason; (2) the choice was permitted but not required by reason; or
(3) the choice was prohibited by reason (was irrational). Assume that our hypothetical
lawmakers choose to promote good A rather than good B. Such a choice is obviously
not required by reason, because we are assuming that the projected instantiations of A
and the projected instantiations of B are rationally incommensurable, which means
that neither a choice for A nor a choice for B is required by rationality.
Nor can we say that the lawmakers’ choice to promote A is prohibited by reason.
I assume that no rule of rationality prohibits the lawmakers from choosing between
conflicting goods whenever those goods are incommensurable. Given the frequency
of incommensurability, any rule requiring lawmaker abstention in the face of incom-
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365
mensurability would unduly restrict the lawmakers’ ability to deal with social prob-
lems. In assuming that the instantiations of good A are rationally incommensurable
with the instantiations of good B, we are assuming that the instantiations of A are not
inferior to the instantiations of B by virtue of the rules of rationality; in other words,
that a choice to promote B is not required by reason.’2 Now, if the rules of rationality
permit the lawmakers to make a choice and do not require a choice in favour of B, a
choice in favour of A is not prohibited by reason. So we cannot judge the lawmakers’
choice of A to be irrational, in the sense of being contrary to the rules of rationality
and thus prohibited by reason.
Of the three possible judgments listed above, the only judgment we can make
about the rational status of the lawmakers’ choice for A is that this choice was per-
mitted but not required by reason, permitted in the sense of not being contrary to the
rules of rationality. So long as rationality does not require abstaining from choice, any
choice between incommensurables would seem to be permitted by reason.
B. Rational Choice and Arational Choice
Choices permitted but not required by reason, however, include two different
kinds of choice. We will use the term “rational choice” to designate any choice that is
not required by reason, but is permitted by reason (not contrary to the rules of ration-
ality) and is also supported by one or more articulable reasons that are both “unde-
feated” and “undefeating”. ‘3 A reason for choosing a particular alternative is unde-
feated if there is no rationally conclusive reason for choosing some other alternative.
A reason for choosing a particular alternative is undefeating if it does not rationally
override the reasons supporting the other alternatives. If the reasons for choosing a
particular alternative were defeated, rather than undefeated, choosing that alternative
would not be permitted by reason. If the reasons for choosing that alternative were de-
feating, rather than undefeating, choosing that alternative would be required by reason.
” If the promotion of A in this situation were prohibited by some moral norm that has been incorpo-
rated into the rules of rationality, while the promotion of B were not so prohibited, the set of A instan-
tiations would be an inferior choice compared to the set of B instantiations, and the two sets of in-
stantiations would be rationally commensurable. But we are assuming that they are rationally incom-
mensurable, and are thus assuming that the rules of rationality do not prohibit the promotion of A
while permitting the promotion of B.
43 Similar conceptions of rational choice are easily found. See e.g. Raz, Morality, supra note 7 at 339
(suggesting that rational action is action for what the agent takes to be an undefeated reason); J. Finnis,
“Concluding Reflections” (1990) 38 Clev. St. L. Rev. 231 at 237-38 (suggesting that choice between
incommensurable options is rational when it is made for reasons “which make that option rationally
appealing” and when the choice “conforms to all the requirements of practical reasonableness”); War-
ner, supra note 7 at 1321-23 (arguing that a choice between incommensurable reasons can be a rational
choice in the sense that the choice is made for reasons that are not defeated by other reasons).
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As the above definitions indicate, the choice of a particular alternative is not a
“rational choice” unless it is supported by articulable reasons that are both undefeated
and undefeating when compared to the reasons supporting the other alternatives.
Thus, in the context of our hypothetical lawmakers choosing between promoting good
A and promoting good B, their choice in favour of A is not a rational choice unless it
is supported by reasons for choosing A over B. The lawmakers have teleological rea-
sons for adopting a rule that would promote good A (A is a basic human good, A can
be instantiated through adoption of rule X), but these are not reasons for choosing A
over B in a conflict situation. (The lawmakers also have similar teleological reasons
for promoting good B by means of rule Y.) To make a rational choice, the lawmakers
also need reasons yielding a comparative judgment about the relative strength of the
teleological reasons for promoting A and the teleological reasons for promoting B.
The reasons for a comparative judgment in favour of A over B would be undefeating
reasons involving norms that are not generally accepted rules of rationality. They
would be reasons that some reasonable persons would reject (we are assuming that
the instantiations of A and the instantiations of B are rationally incommensurable, i.e.,
that a choice in favour of A is not rationally required) but they would provide some
rational support for a choice in favour of good A over good B, and that choice would
thus deserve to be called rational.
A second kind of choice permitted but not required by reason must now be distin-
guished from rational choice. A choice of this second type is not supported by any ar-
ticulable reason suggesting that that choice is better than any alternative choice. We
will refer to any such choice as an “arational choice”. Like the rational choice, the
arational choice is not contrary to the rules of rationality and is thus permitted by rea-
son. Unlike the rational choice, however, the arational choice is not made for any ar-
ticulable reason yielding a judgment about the comparative merits of the available al-
ternatives. The decision to choose one alternative over the other is not the result of a
reasoning process. It may be the result of an intuitive judgment based on subcon-
scious and inarticulable factors. It may even be entirely arbitrary, so long as it is made
in a context in which the rules of rationality do not prohibit arbitrary choice. In most
law-making contexts, arbitrary choice is probably prohibited by applicable rules of
rationality and would thus be irrational (contrary to reason), rather than arational and
permitted by reason.”
“When a choice between incommensurables is irrational because arbitrary, what is irrational (con-
trary to the rules of rationality) is not the content of the choice (for example, a preference for good A
over good B), but the way in which the choice is made (arbitrarily). We are assuming that the con-
flicting goods are rationally incommensurable, and must therefore assume that reason permits a
choice for A and permits a choice for B.
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
367
We have seen that when lawmakers choose between rationally incommensurable
goods (or, more likely, between rationally incommensurable instantiations of one or
more goods), their choice cannot be required by reason. Nor will their choice be pro-
hibited by reason or contrary to reason, so long as it is not arbitrary or otherwise in
violation of the rules of rationality governing the lawmakers. ‘ In most cases, their
choice will be permitted by reason. We will now see that lawmakers have a number of
resources that enable them to make choices that are not only permitted by reason, but
actually have considerable support, so that, although they are not required by reason,
they deserve our intellectual and moral respect.
C. Moral Principles
One such resource will be a set of moral principles that a lawmaker has accepted
as normative guidelines for law-making. We expect lawmakers to use moral principles
and would think that something was wrong if a lawmaker was not guided by moral
principles. The moral principles I have in mind are principles that are not required by
the rules of rationality. (If a particular choice were dictated by a moral principle that is
incorporated into the rules of rationality, that choice would be required by reason; we
are now dealing with law-making choices that are merely permitted, and not required,
by reason.) I do not profess to know which moral principles are requirements of ra-
tionality and which are not. I suspect that most of the moral principles used by law-
makers are not principles that every, or almost every, rational person would accept,
and thus are not mandatory rules of rationality.
For example, a lawmaker might employ a moral principle of distributive justice
whereby scarce educational opportunities related to the professions (admission to
state law schools, for example) should be distributed according to merit, with merit
being defined broadly so as to include factors such as the likelihood that candidates
will use their education to serve citizens with the greatest need for their services. This
moral principle is not generally accepted in our society and has certainly not been in-
corporated into our rules of rationality. Many North Americans hold that scarce edu-
cational opportunities should be distributed according to merit, with merit narrowly
defined as a matter of past grades and standard test scores. The two positions conflict,
but neither is irrational. When a lawmaker votes for a legal rule specifying criteria that
may be used or may not be used in distributing scarce educational opportunities, he or
she will be choosing among alternative sets of instantiations of the basic human goods
reason because of the way it is made. See supra note 44.
” Even then, the content of the choice will not be contrary to reason. The choice will be contrary to
6 See Grisez, supra note 35 at 59 (suggesting that in constructing a legal system, lawmakers should
be guided by moral norms when they choose between the incommensurable goods that ought to be
protected by law).
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of knowledge and meaningful work. Each alternative legal rule will instantiate these
goods somewhat unpredictably in different ways and in a different set of human lives.
The instantiations will therefore probably be rationally incommensurable. If the law-
maker resolves the conflict between incommensurables by using a meritarian princi-
ple of distributive justice that defines merit broadly, his or her choice will not be re-
quired by reason or prohibited by reason. It will be permitted by reason. Yet we can
say more than this. We can say that his or her choice is a rational choice, supported by
a reason in the form of a moral principle that could explain why one choice is better than
its alternatives. This moral principle of justice provides a premise concerning what
counts as merit, and this premise leads to a decision favouring one legal rule over alter-
native legal rules. The premise can itself be supported by arguments concerning the
state’s duty to train professionals who will benefit society and promote the common
good. These arguments and this premise can be rejected by rational persons. But no is-
sue-resolving legal argument begins with premises, all of which are required by reason
and invulnerable to rational objection. Practical reason does not require the impossible.
D. Social Traditions
Although lawmakers may not accept a particular norm as a moral truth, they may
feel obligated to employ that norm in their law-making activity if the norm has been
established as an important tradition in their society. (This sense of obligation will be
especially strong if the tradition has been a source of constitutional doctrine or a basis
for legal rules in other areas of law.) Such social traditions provide a second type of
resource for lawmakers who must choose between incommensurable goods or instan-
tiations. Even though the conflicting goods cannot be ranked in any objective, ration-
ally compelling hierarchy, a society might establish its own subjective ranking. Law-
makers can resolve conflicts between incommensurables by respecting such social
rankings.’
For example, a lawmaker might believe that the goods of education and religion
are more important than any conflicting good of religious liberty, and that the ideal
state would subsidize educational institutions operated by religious organizations.
Nevertheless, this lawmaker might vote against a proposal for a particular form of
merely partial and indirect subsidization because it seems contrary to a firm and long-
” See J. Gray, Post-liberalism: Studies in Political Thought (New York: Routledge, 1993) at 325
(interpreting Isaiah Berlin as holding that conflicts between incommensurable conceptions of the
good may properly be resolved by social tradition). At one point, Berlin himself goes even further and
suggests that the choice between conflicting goods is ultimately “dictated by the forms of life of the
society to which one belongs …” See Berlin, Crooked Timber, supra note 2 at 17-18. See also Kekes,
Pluralism, supra note 36 at 60-63 (arguing that the social resolution of conflicts between incommen-
surable values requires a tradition, an ordered set of social conventions).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILI7Y
369
standing social tradition requiring strict separation of church and state. Even though
this separation principle is not accepted as a moral truth, the lawmaker uses it to re-
solve a conflict between incommensurables because of its status as a social tradition.
Our hypothetical lawmaker’s use of a social tradition is not irrational. It is not
prohibited by reason. Assuming that the conflicting goods are rationally incommensu-
rable, such a choice would be permitted by reason.” Furthermore, a choice made on
the basis of a social tradition is a rational choice when supported by undefeated rea-
sons, such as the reasons for the particular tradition and the reasons for respecting tra-
ditions in general.
E. Prudential Principles
Some principles of prudence may not qualify as either moral principles or estab-
lished social traditions but may nonetheless serve as reasonable guidelines for law-
makers who seek to resolve conflicts between incommensurable goods or instantia-
tions. These prudential principles tend to be pragmatic law-making techniques, rather
than requirements of justice, but they make up an important part of political wisdom
and can be used to resolve conflicts in ways that reduce social friction and provide
smoother sailing for the ship of state.
” See Kekes, Pluralism, ibid at 56 (stating that incommensurability merely precludes the possibility
of any ranking of values that is based on intrinsic characteristics and would be acceptable to all reason-
able persons (required by reason)), 76-78 (suggesting that conflicts between incommensurable values
can be reasonably resolved by social traditions); Finnis, “Commensuration”, supra note 10 at 233 (ar-
guing that community commitments enable societies to reasonably rank options that are rationally in-
commensurable).
Even if a society were to establish traditions fixing some or all basic human goods in an absolute
hierarchy, that need not be irrational. It might seem that any such absolute hierarchy is somehow in-
consistent with an acknowledgment that the goods are rationally incommensurable, that the rules of
rationality do not yield ordinal commensurability among the goods as abstract concepts. But such an
acknowledgment merely precludes the claim that a particular ranking is required by reason; it does
not prohibit a society from making a subjective ranking and making it absolute. It would seem that a
fixed, absolute social ranking of rationally incommensurable abstract goods is irrational only where
(1) the instantiations of such goods are rationally commensurable, and (2) instantiations of one such
good are sometimes superior, and sometimes inferior, to instantiations of another such good. In such a
situation, it would be irrational always to treat good A as superior to good B when reason dictates that
instantiations of B are sometimes superior to instantiations of A. But where the abstract goods and
their instantiations are always rationally incommensurable, reason permits society to subjectively rank
abstract goods in any fashion, including a fixed, absolute hierarchy. See, however, text accompanying
note 36 above, suggesting that even instantiations of different abstract basic goods may sometimes be
rationally commensurable.
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One such principle provides that lawmakers should try to reach a compromise or
balance between conflicting social interests. Legislative or judicial compromise is of-
ten useful in avoiding the radical political disaffection that can result when one inter-
est group’s goals are entirely frustrated. Conflicts between social interests are apt to
be conflicts between incommensurable sets of instantiations of basic human goods.
The compromise principle suggests that lawmakers resolve such conflicts by producing
legal rules that provide each group with at least some of the particular good it desires. ‘9
When a particular legal issue involves two conflicting basic abstract goods, one of
which is preferred by some persons while the other is preferred by other persons, and
the lawmakers can fashion a rule that promotes both goods to some extent, but more
of either good entails less of the other good, the lawmakers can compromise by se-
lecting a legal rule that promotes each good to a moderate degree, rather than a rule
that promotes one good to a high degree and promotes the other good to a low degree
or not at all. When only one basic abstract good is involved, and the lawmakers are
choosing between alternative sets of instantiations of that good, the lawmakers may
be able to compromise by selecting a legal rule that is likely to produce at least some
instantiations of that good for every interested citizen, rather than a rule that will pro-
vide abundant instantiations to one interest group and no instantiations to a competing
interest group.
Even when the particular legal issue does not permit compromise, lawmakers can
seek an overall balance between conflicting goods or between citizens. In choosing
between two basic abstract goods that are totally incompatible in the context of the
particular legal issue (totally incompatible in the sense that each alternative legal rule
can promote one good but not the other), the lawmakers can choose to promote the
good that has been less favoured in other law-making decisions. Such a choice tends
to compensate for past law-making decisions that largely ignored a particular basic
abstract good; it thus tends to provide society with a more balanced array of basic
human goods.
In choosing between alternative sets of instantiations of the same abstract good,
where no matter which legal rule is selected all the instantiations will benefit one
” A number of commentators have suggested that compromise is a good way to resolve conflicts
between incommensurable values. See e.g. Berlin, Crooked Timber, supra note 2 at 47 (proposing that
when ultimate values are incompatible, “perhaps, the best one can do is to try to promote some kind
of equilibrium … between the different aspirations of different groups of human beings”); Kekes, Plu-
ralism, ibid. at 88-89 (suggesting that some conflicts between incommensurable values can be re-
solved by achieving a compromise between the conflicting values); A.T. Kronman, The Lost Lawyer:
Failing Ideals of the Legal Profession (Cambridge, Mass.: Belknap Press of Harvard University Press,
1993) at 88-92 (suggesting that conflicts between conflicting and incommensurable values should be
resolved through compromise, or at least dealt with by lawmakers in a way that promotes political
fraternity).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
group of citizens while another group of citizens gets nothing, the lawmakers can
choose a legal rule that favours the group of citizens who were less favoured in past
law-making decisions involving the distribution of that same abstract good.
Applying a principle of compromise or overall balance will seldom be as simple
as I have described it. Conflict situations will be more complex, and judgments will
be even more imprecise. But some such principle will often provide a reasonable way
of resolving conflicts between incommensurable goods or instantiations. When the
resolution is supported by reasons (social harmony, social stability, availability of all
basic human goods, equilibrium among basic human goods, or concern for the needs
of each citizen), it can even be a rational choice, as we have defined that term.
F. Intuition
When a conflict between rationally incommensurable goods or instantiations
cannot be resolved by moral or prudential principles, or by social traditions, lawmak-
ers can make an intuitive moral choice. A moral intuition is an immediate judgment,
made without any conscious process of inference.’ It is the product of unanalyzed ex-
perience’ Stuart Hampshire describes the analogous intuition of the connoisseur:
Connoisseurs … are … able to discriminate with consistent success, but not
knowing at all precisely how they do it. … They know that … they are guided by
a weight of experience of many similar cases and by many associations and
memories, not all of which they can disentangle and recall. The memories are
too extensive to be accessible, but methodically stored and linked by a causality
which they do not understand and which is too complex to trace. The connois-
seur … must not impose a ready-made rational structure on his observations, if
this entails attending to ordinarily expected features … and attending only with
set ideas of what is relevant.
The connoisseur may never know, and be able to distinguish, the separate
steps, or the separate inputs, which led him to his conclusion, and he may never
be able to put his inference into any standard form.’2
When lawmakers make an intuitive choice between incommensurables (typically
a choice between incommensurable instantiations of one or more abstract goods), the
choice cannot be rational (as we have defined this term), because it is not made for
articulable reasons. The lawmakers may have articulable reasons for desiring one al-
ternative, and articulable reasons for desiring the other alternative, but they do not
have articulable reasons for choosing the chosen alternative over the other alternative.
30See Hampshire, supra note 3 at 15-16.
I’ Ibid at 14.
52/bid at 111.
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However, the intuitive choice is not necessarily irrational.”3 If our intuitions in a par-
ticular context are based on extensive experience and have generally proven to be sat-
isfactory, it is rational to continue to follow them. There are thus situations in which
we should follow our moral intuitions, even though we cannot specify the reasons
supporting them.’ Lawmakers typically have extensive experience in making intuitive
moral judgments. When they must choose between incommensurables, and logic fails
and reason runs out, they may properly resort to intuition.”
Intuition is often necessary in framing a legal compromise. When lawmakers es-
tablish a speed limit for a particular highway, they will probably want to achieve a
compromise between preserving human life and health, and facilitating recreation,
friendship, and commerce through speedy transportation. But even with abundant in-
formation about accident rates at various speeds, the lawmakers must use intuition in
deciding whether the speed limit should be set at 45 miles per hour or at 55 miles per
hour. In addition to legal compromises, there are many other law-making decisions
that ultimately depend upon intuition. For example, when the good called liberty con-
flicts with the good called equality or the good called security, there is often no rele-
vant moral principle or social tradition to apply, and no opportunity for compromise
or balancing. Here the lawmakers’ choice between permitting all acts of a certain type
and prohibiting all acts of that type must be largely intuitive.
III. The Jurisprudential Implications of Incommensurability
A number of writers claim that the incommensurability thesis has significant sub-
stantive implications for jurisprudence and public policy. Part IN will examine some
of the claims most often asserted.
A. Arguments against Consequentialism
Does acceptance of the incommensurability thesis imply the rejection of conse-
quentialism as a comprehensive guide to moral choice in law-making?’ Utilitarian-
51 Compare ibid. at 14 (arguing that intuitive beliefs are not normally rendered irrational by the be-
liever’s inability to explain why the belief is held).
5″ See ibid. at 111 (arguing that “we ought sometimes, even in serious issues of public policy, to
follow our moral intuitions”).
55 See Saint Thomas Aquinas, The Treatise on Law, ed. and trans. by R.J. Henle (Notre Dame, Ind.:
University of Notre Dame Press, 1993) at 74-75 (editor’s summary of Aquinas: in hard cases, where
there are a number of heterogeneous factors lacking any common denominator, logic fails and in-
sight-a direct apprehension not arrived at by applying rules of inference-must take over).
-6 We noted above in Part I.B.2 that conflicting instantiations of one or more basic human goods
may sometimes be commensurable. In such pockets of commensurability, consequentialism may be
an appropriate decision procedure for lawmakers. And if it is inappropriate, this cannot be due to any
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
ism, welfare economics, cost-benefit analysis, Economic Analysis of Law, and many
other forms of consequentialism prescribe that lawmakers always choose the legal
rule that has expected consequences that maximize net aggregate value throughout
society (the rule that is likely to produce a greater amount of net aggregate value than
any alternative rule would).7 However value is conceived (as utility, welfare, eco-
nomic wealth, or something else), it is to be maximized on net (with total losses in
value subtracted from total gains in value) and in the aggregate (what counts is net
value for society, not net value for any individual citizen). Any such consequentialist
approach obviously requires some attempt to measure and compare the value inhering
in different predicted consequences, different states of affairs that might be brought
about by different legal rules.
It is thus not surprising that a number of writers have claimed that consequential-
ism must be rejected because it requires the metrical commensuration of goods or in-
stantiations that are usually incommensurable in value.”
incommensurability. The thesis that incommensurability is widespread thus does not imply that con-
sequentialist methods should never be used by lawmakers. In this section, we are dealing with the
question whether consequentialist methods should be avoided in the numerous situations of incom-
mensurability, or, in other words, whether widespread incommensurability implies that consequen-
tialism is not suitable as a comprehensive method for all or most situations.
Although there are other possible approaches that evaluate an act of law-making solely in terms of
its consequences, I will use the term “consequentialism” in a restricted sense that refers to the quanti-
tative maximization type of theory described in the text.
” See e.g. Fmnis, Natural Law, supra note 30 at 112-13, 115 (arguing that as a general strategy of
moral reasoning, consequentialism is irrational because it pretends to commensurate basic goods that
lack a common yardstick and are incommensurable; the notion of the greatest net good is not merely
unworkable, but senseless); Raz, Morality, supra note 7 at 358 (suggesting that widespread incom-
mensurability undermines consequentialist maximization as a general system of practical reasoning);
J. Finnis, “Natural Law and Legal Reasoning” in R.P. George, ed., Natural Law Theory: Contempo-
rary Essays (Oxford: Clarendon Press, 1992) 134 at 150-51 [hereinafter Fmnis, “Legal Reasoning”]
(arguing that incommensurability rules out Economic Analysis of Law, which attempts to resolve so-
cial issues by using wealth as a commensurating maximand); Grisez, supra note 35 at 29 (arguing
that consequentialism is rationally unacceptable because the notion of the “greater good” lacks refer-
ence; it implies that goods are measurable and commensurable, but goods cannot be measured by any
common standard); M.C. Nussbaum, ‘lawed Foundations: The Philosophical Critique of (a Particu-
lar Type of) Economics” (1997) 64 U. Chi. L. Rev. 1197 at 1199 (noting that Law and Economics is
committed to the commensurability of all ends), 1202 (suggesting that it is irrational to treat two ends
as commensurable when there is good reason to think they are not); R.P. George, “Recent Criticism of
Natural Law Theory,” Book Review of Natural Law and Justice by LL. Weinreb and A Crtique of
the New Natural Law Theory by R. Hittinger (1988) 55 U. Chi. L. Rev. 1371 at 1395 (summarizing
Grisez and Fmnis as rejecting the consequentialist principle of producing the greatest net proportion
of good to bad consequences, because it falsely assumes that the instantiations of human goods and
bads are commensurable in a way that permits the measuring of value necessary for consequentialist
calculations).
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A good example of the argument that incommensurability entails the rejection of
consequentialism is provided by John Finnis as a “response to notions that social
choice can and should be guided by measuring the expected value of alternative fore-
seeable outcomes”59 Finnis readily acknowledges that “[c]ommensuration of the
goods and bads in alternative available courses of action is possible … in the techni-
cal domain'” the proper domain of cost-benefit analysis.’ In this technical domain, all
significant costs and benefits can be quantified and compared by means of some defi-
nite unit of value (money, for example) that renders them commensurable.” But, says
Finnis, law-making involves deliberation, not in the technical domain, but in the very
different domain of morally significant choice. 2 In the domain of morally significant
choice, none of the features of the technical domain, such as quantifiability and com-
mensuration of costs and benefits, are present. 3 Thus,
it is not possible to commensurate … the goods and bads in alternative avail-
able courses of action considered as options between which an individual or
group has occasion to make a morally significant choice. In particular, it is not
possible to make the type of commensuration required by utilitarianism in any
of its forms, or by its consequentialist or proportionalist or economistic suc-
cessor-S. 4
64
Finnis seems to be saying that consequentialist approaches to law-making must be
rejected because they require metrical commensurability among instantiations (of
human goods) that are metrically incommensurable. Consequentialist methods are
precluded by “the incommensurability of the goodness of alternative options.”‘
When Finnis refers to incommensurability, he is apparently referring to what I
call rational incommensurability, as opposed to incommensurability as a matter of real
moral truth.’ Herein lies the problem in Finnis’s argument and all similar arguments.
If two basic goods or two sets of instantiations of basic goods or two law-making op-
tions are rationally incommensurable, neither is better than the other as a matter of
reason. Neither alternative is required by reason to be chosen, as would be the case if
one were the better alternative. As well, neither alternative is prohibited by reason, as
would be the case if one were the worse alternative. If neither alternative is required
by reason, and neither alternative is prohibited by reason, each alternative must be
59 Finnis, “Commensuration”, supra note 10 at 218.
at 218-19.
0Ibid.
6
6 Ibid. at 219.
62 Ibid
63 Ibid
‘*Ibid
6 Ibid
66See ibid at 233 (referring to “options which by reason’s own standards are incommensurable”
and “options neither (or none) of which is required by reason’s principles and norms”).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
375
permitted by reason. As far as rationality is concerned, choosing one alternative based
on consequentialist calculations is no better or worse than choosing the other alterna-
tive as a matter of purely intuitive choice.
It may be objected that while reason permits either rationally incommensurable
alternative to be chosen, it does not permit lawmakers to employ consequentialist de-
cision procedures in reaching that choice. I think the objection fails. Surely, there is
no rule of rationality prohibiting lawmakers from subjectively ranking alternatives
that are rationally incommensurable. If there were, the enterprise of law-making
would collapse. Is there a rule of rationality prohibiting lawmakers from ranking ra-
tionally incommensurable alternatives in terms of aggregates of cardinal numbers rep-
resenting presumed individual utilities or presumed individual willingness to pay for
something? It is difficult to see how reason could prohibit such consequentialist deci-
sion procedures if it permits purely intuitive or subjective rankings.
In any event, no rule prohibiting consequentialist decision procedures has been
generally accepted as a rule of rationality. Rules of rationality are established only by
general acceptance, seen in social practices. Just as there is no private language, there
is no private rationality. It therefore follows that consequentialist decision procedures
are not prohibited by reason when lawmakers choose between rationally incommen-
surable alternatives.’ The incommensurability thesis, employed in conjunction with
the rules of rationality, does not imply that we should reject consequentialism.
The rational incommensurability of basic goods or their instantiations merely im-
plies that lawmakers must go beyond objective rationality in making their choices.
The only forms of consequentialism that are incompatible with rational incommen-
surability are dogmatic forms asserting that certain consequentialist decision proce-
dures and particular determinate choices are required by reason. Cost-benefit analysis,
welfare economics, the Economic Analysis of Law, and similar consequentialist ap-
proaches can probably be interpreted as non-dogmatic theories that do not claim that
their methods are required by reason.’ There are good reasons to reject consequen-
tialist theories as comprehensive approaches to jurisprudence. The thesis of wide-
67 See M. Adler, “Incommensurability and Cost-Benefit Analysis” (1998) 146 U. Pa. L. Rev. 1371
at 1401 (arguing that the fact that cost-benefit analysis fails to represent how incomparable options
relate does not count as a reason against the use of cost-benefit analysis in favour of some other deci-
sion procedure), 1406-07 (arguing that assigning numerical rankings of incomparable options in a
cost-benefit analysis is not in itself better or worse than any alternative decision procedure).
‘ See Craswell, supra note 12 at 1424 (suggesting that metrical incommensurability does not un-
dermine welfare economics: welfare economics uses presumed individual choices without claiming
that such choices would be justified), 1449 (suggesting that welfare economics uses social welfare
functions (such as the Kaldor-Hicks criterion) to rank social choice options without claiming that the
social welfare function justifies the choice).
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spread rational incommensurability among basic goods and among instantiations is
not one of them.
B. Arguments for Liberalism
According to John Rawls, a crucial assumption of liberalism is that there are
many conflicting, reasonable, and incommensurable conceptions of the good.’ In-
deed, liberals do sometimes suggest that incommensurability of goods, or conceptions
of the good, implies certain liberal doctrines requiring extensive individual liberty, the
widest possible diversity of ways of life, government neutrality about the good, or the
use of free markets.
1.
Individual Liberty
A common theme in liberal philosophy is that a political system should give indi-
vidual liberty a high priority among human values. It has been suggested that the spe-
cial status of liberty stems from the plurality and incommensurability of human
goods.”
Rational incommensurability among goods, however, does not in itself entail that
liberty should have priority over other goods.” If certain goods are rationally incom-
mensurable, no one of those goods is superior to the others as a matter of reason. This
is what rational incommensurability means. There may be good reasons for regarding
liberty as a high-priority value, but no priority for liberty can be derived by logical
implication from incommensurability.
Not only does incommensurability not imply a priority for liberty, it does not even
imply that the legal system should accord citizens a wide zone of unfettered negative
liberty. When good A and good B conflict, and a citizen must pursue one good or the
other, a choice must be made. An assertion that the goods are rationally incommensu-
rable, however, does not imply anything as to who should make that choice, whether
it should be the citizen or the state. The state might decide: to leave the citizen free to
make his or her own choice, to prevent the citizen from pursuing good A, or to pre-
vent the citizen from pursuing good B. If the alternative instantiations of goods that
69 See J. RawIs, Political Liberalism (New York: Columbia University Press, 1996) at 135, 303.
70 See Berlin, Four Essays, supra note 3 at 171 (stating that pluralism, which recognizes that human
goals are many and not always commensurable, entails a large measure of negative liberty); see also
Gray, Berlin, supra note 37 at 143-44 (interpreting Berlin as arguing that if goods are rationally in-
commensurable, the state cannot have any “good reason to impose any particular combination of
them on any of its citizens” [emphasis in original]).
” See Gray, Enlightenment’s Wake, supra note 19 at 133 (noting that a priority for one value, liberty,
does not follow from “the truth of a plurality of incommensurable values”).
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can be pursued by the citizen are rationally incommensurable, none of the state’s al-
ternatives is required by reason or prohibited by reason. As far as reason is concerned,
the state’s officials are free to make a subjective choice. Because the goods and in-
stantiations at stake are rationally incommensurable, the citizen can have no rationally
compelling ground for objecting that the state imposed the wrong choice on him or
her, just as the state officials can have no rationally compelling ground for claiming
that they made the correct choice. Incommensurability, by itself, does not even imply
that it would be wrong for lawmakers to coercively impose their own value ranking
on citizens in every situation where conflicting goods or instantiations are incommen-
surable.
The rational incommensurability of basic goods or their instantiations implies a
large measure of individual liberty only if this incommensurability premise is used in
conjunction with a second premise asserting that the state should allow freedom of
choice for citizens in any conflict situation where reasonable persons could disagree
about how a conflict between goods or instantiations should be resolved. If the con-
flicting goods or instantiations are rationally incommensurable, reason does not re-
quire any particular choice. Reasonable persons could therefore disagree in their
choices, and according to the second premise, the state must allow freedom of choice
whenever such reasonable disagreement is possible. This second premise has been
advanced by a number of liberal thinkers. ‘
The problem with this argument is that the second premise is not plausible. On
most important moral issues involving conflicting goods or instantiations, reasonable
people (persons who do not violate any of the socially established rules of rationality)
would disagree. They would adhere to different principles of justice, and they would
resolve conflicts between incommensurable goods or instantiations in differing ways.
Acceptance of the second premise would thus paralyze lawmakers. It would not only
prevent lawmakers from resolving those everyday interpersonal conflicts that are
really conflicts between competing but incommensurable goods or instantiations, it
would preclude lawmakers from establishing basic constitutional principles fixing the
‘ See Rawls, supra note 69 at 139-40 (asserting that when constitutional essentials and basic ques-
tions of justice are at stake, the coercive power of the state should be exercised “only in ways that all
citizens can reasonably be expected to endorse in the light of their common human reason”); J. Wal-
dron, Liberal Rights: Collected Papers 1981-1991 (Cambridge: Cambridge University Press, 1993) at
50-57 (suggesting that the fundamental liberal thesis is that political action is not morally justified
without the hypothetical consent of all reasonable citizens); W.A. Galston, “The Legal and Political
Implications of Moral Pluralism” (1998) 57 Md. L. Rev. 236 at 242 (asserting that the liberty of indi-
viduals should not be restricted by the state without a rationally binding reason, and arguing that be-
cause no rationally binding reason is available for choosing between incommensurable values, citi-
zens should be allowed to make their own free choices among such incommensurable values).
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scope of those fundamental rights that protect important goods but whose precise
boundaries are so obviously and reasonably controversial.
2. Diversity
A liberal might acknowledge that the desirability of extensive liberty is not di-
rectly implied by the incommensurability of goods, and then make a different argu-
ment for liberty: extensive individual liberty is necessary for the widest possible di-
versity of lifestyles or ways of life. If citizens are not free to choose among all the ba-
sic goods and free to use a sufficiently wide variety of modes of instantiating those
goods, the diversity of ways of life will be reduced. The maximization of this diversity
is a worthy goal, because “[c]ivilization is a garden made rich and beautiful by the va-
riety of its flowers.” 3
The incommensurability thesis does not, however, entail this goal of diversity.
The notion that a number of alternative ways of life are rationally incommensurable
because they combine incommensurable goods in different ways does not imply that
society should tolerate or promote as many of these ways of life as possible; it merely
asserts that none of these ways of life is required by reason or prohibited by reason.
Reason leaves society free to foster all of the incommensurable ways of life or to al-
low only one of them.
Liberal diversity is implied by a form of pluralism that identifies a number of ba-
sic goods; asserts that individuals can have good lives only if they realize all of these
basic goods; further asserts that because individuals differ in their capacities and ap-
titudes, they need a wide variety of modes of instantiating each basic good; and as-
serts finally that the state should promote good lives for all citizens. Such a pluralistic
theory does not imply that the legal system should tolerate all possible modes of in-
stantiating basic goods; it merely suggests that the legal system should permit enough
modes so that each citizen can realize each of the basic goods. The theory, however,
does entail allowing a wide diversity of ways of life. It condemns any law that totally
precludes citizens from pursuing one of the necessary basic goods. It also condemns
any law that prohibits citizens from instantiating a basic good in the only mode of
which they are capable. In this argument, however, it is not incommensurability that
implies a wide diversity of ways of life (incommensurability is not even mentioned),
rather a particular version of value-pluralism.
” Berlin, Crooked imber, supra note 2 at 223. See also Gray, Berlin, supra note 37 at 36 (inter-
preting Berlin as holding that liberal liberty is justified because “it permits a … greater variety of
forms of self-creation through choice-making”), 144 (interpreting Berlin as holding that a good rea-
son for the state not to impose a particular pattern of incommensurable goods is that any such imposi-
tion would reduce the number of goods and combinations of goods actually realized).
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379
3. State Neutrality
A number of liberal theorists assert that lawmakers should be neutral as to rival
conceptions of the good.: This neutrality thesis is clearly not implied by the incom-
mensurability of basic human goods or by the incommensurability of various concep-
tions of the good, conceptions that rank the basic goods in different ways and may not
even recognize the same set of basic goods. The rational incommensurability of rival
conceptions of the good merely means that reason does not require a judgment that
one conception of the good is superior to another or a judgment that the conceptions
are equally sound. Rational incommensurability by itself implies nothing as to the
question of whether lawmakers should promote one conception of the good or remain
neutral about conceptions of the good. Reason leaves lawmakers free to take either ap-
proach. The incommensurability thesis is thus neutral about the state neutrality thesis.
Some of the liberals who assert the neutrality thesis combine an incommensura-
bility premise with another premise very similar to the one described above in our
discussion of individual liberty. The argument goes something like this:
(1) The state should impose or promote a particular conception of the good only
if that conception would be endorsed by all reasonable citizens, and the state should
suppress a particular conception of the good only if that conception would be rejected
by all reasonable citizens;
(2) Except for conceptions that all reasonable citizens would reject, conceptions
of the good are rationally incommensurable with each other (reason does not require
the endorsement or rejection of any of them); therefore,
(3) Although the state may justifiably suppress a conception that all reasonable
citizens would reject, the state should not otherwise impose, promote, or suppress any
conception of the good.”
74See e.g. B. Barry, Justice as Impartiality: A Treatise on Social Justice, vol. 2 (Oxford: Clarendon
Press, 1995) at 12 (suggesting that impartial justice requires neutrality among conflicting conceptions
of the good); R. Dworkin, A Matter of Principle (Cambridge, Mass.: Harvard University Press, 1985)
at 191-92 (stating, as an important principle of liberalism, that government must be neutral toward
conceptions of the good life); Waldron, supra note 72 at 160-63 (presenting the liberal view that law-
makers should be neutral about conceptions of the good life).
75 Although the argument is usually not this explicit, it can be traced in a number of liberal works.
See Barry, ibid at 7, 160-73 (arguing that a basic constitutional principle should be imposed on citi-
zens only if it could not be reasonably rejected by any citizen, that all conceptions of the good can be
reasonably rejected, and that, therefore, no conception of the good should be imposed as a basic con-
stitutional principle); C.E. Larmore, Patterns of Moral Complexity (Cambridge: Cambridge Univer-
sity Press, 1987) at 22-23 (presenting the liberal assertion that conceptions of the good are plural and
incommensurable), 68 (presenting the liberal notion that “reasonable people differ and disagree about
the nature of the good life”), 42-44 (suggesting that the liberal proposal for state neutrality as to con-
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I have inserted the exceptions involving conceptions that all reasonable citizens
would reject, because I presume that liberal neutralists would acknowledge that al-
though there is no conception of the good that all reasonable citizens would endorse,
there are some conceptions that all reasonable citizens would reject (for example,
conceptions that violate rational requirements of consistency).
So stated, the argument seems to be a valid inference; if the premises are ac-
cepted, the conclusion must be accepted. The problem is that premise (1) is not ten-
able. Like the similar premise in the liberty argument examined above, its acceptance
would paralyze lawmakers. If lawmakers were allowed to use only those conceptions
of the good that all reasonable citizens would endorse, that is, conceptions required by
the generally accepted rules of rationality, lawmakers would not be allowed to use any
conception of the good if all rationally permissible conceptions are rationally incom-
mensurable with each other. The legal system could no longer promote human life or
human health or the advancement of human knowledge; these goods are components
of conceptions of the good, and any legislation that promotes such goods would fa-
vour the conceptions of which they are components, conceptions toward which the
government is supposed to remain neutral. Denied the right to use any conception of
the good, lawmakers would have to rely on deontological principles lacking any basis
in notions of human well-being. Government’s duty to promote the welfare of its citi-
zens would become an empty relic of a pre-neutralist age; welfare could not be given
any meaning because lawmakers would be prohibited from using any conception of
the good life.
4. Free Markets
Liberals typically agree that an economic system should rely on free markets to a
great extent. Cass Sunstein notes that the incommensurable ways in which people
value goods may explain why liberals generally favour voluntary free-market ex-
change:
If people value things in different ways, the state should allow them to sort
things out as they choose. If values were commensurable, perhaps we could
seek to block certain voluntary exchanges simply because we had better infor-
mation about relevant costs and benefits than the parties themselves. But, in the
ceptions of the good life is a response to pluralistic conceptions of the good life and reasonable dis-
agreement); Rawls, supra note 69 at 303 (stating that liberalism assumes that equal citizens have dif-
ferent and incommensurable conceptions of the good), 135 (stating that there are many conflicting but
reasonable and rational conceptions of the good), 137 (suggesting that the exercise of political power
is justified only when it is in accordance with principles that all reasonable citizens would accept). For
an explication of the two-premise neutrality argument, similar to that in my text, see S. Gardbaum,
“Liberalism, Autonomy, and Moral Conflict” (1996) 48 Stan. L. Rev. 385 at 389.
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face of diverse kinds of valuation, it is best to permit people to value as they
like.
76
Suppose that Sam Seller owns an automobile and values it low enough so that he
would be willing to sell it for $5000. Betty Buyer values Seller’s automobile high
enough so that she would be willing to pay $7000 for it. If the automobile is rationally
incommensurable in value with any particular amount of money, neither Seller’s sub-
jective valuation of $5000 nor Buyer’s subjective valuation of $7000 is contrary to
reason. If, in the absence of commensurability, what counts is any person’s subjective
valuation, Seller’s sale of the automobile to Buyer for $6000 would be mutually bene-
ficial and should be permitted:’
Sunstein suggests, however, that some exchanges are justifiably prohibited by
law.”9 An exchange may produce negative externalities, harms to third persons who
were not parties to, and did not consent to, the exchange. Market sales of babies, for
example, could have negative effects on the babies (there is little reason to suppose
that the highest bidders are also suitable parents) and could have negative effects on
other members of society (such sales could lead people to value babies in ways that
impair or destroy a traditional parent-child relationship that many of us value).9 These
negative externalities may exceed the sum of net benefits to the parties and positive
externalities. If so, lawmakers have a good reason to block the exchange.
If the harms and benefits resulting from a series of exchanges are rationally in-
commensurable, reason does not indicate whether the harms exceed the benefits. We
have been assuming that when valuations of goods are rationally incommensurable,
subjective valuations may properly be used. When an exchange produces negative
externalities, however, we usually cannot ascertain the subjective (negative) valuations
of the third-party victims. We would not want to believe what the victims tell us, for
they would probably overstate their losses.
This was not a problem in our automobile hypothetical, in which we were con-
cerned only with Sam Seller and Betty Buyer. We could not know that Seller valued
the car at $5000 or that Buyer valued the car at $7000. But in the absence of fraud or
duress, we could safely assume that if the car was actually sold for $6000, Seller val-
ued the car at less than $6000 and Buyer valued the car at more than $6000, so that
76 Sunstein, supra note 12 at 849.
” This is another example of the liberal premise (already noted in connection with individual liberty
and state neutrality) that when reasonable people can disagree about valuations of goods, citizens
should be permitted to do whatever they want to do. The upshot is that the more incommensurability
we recognize, the closer we come to anarchy. Liberals beware! (Not of incommensurability, but of the
notion that incommensurability precludes legal regulation.)
7
1 Sunstein, supra note 12 at 849-50.
71 See ibiL at 850.
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both parties would receive net subjective benefits. We can make no similar assump-
tions, however, concerning the subjective valuations of third parties who never con-
sented to an exchange.
When the consequences of an exchange are rationally incommensurable and we
cannot adequately ascertain the subjective valuations of all persons affected by the ex-
change because externalities are involved, should lawmakers permit the exchange or
block the exchange? However we answer this question, our answer will not be en-
tailed by the incommensurability of different ways of valuing goods or instantiations.
If voluntary exchanges seldom produced negative externalities, incommensura-
bility in conjunction with a premise honouring subjective evaluations in the presence
of rational incommensurability would seem to imply very extensive use of free mar-
kets. Our world, however, is replete with negative externalities, and thus few of the
relevant subjective valuations are ascertainable, and incommensurability implies nei-
ther widespread use nor greatly restricted use of free markets. It does not imply that
most market exchanges should be permitted, just as it does not imply that market ex-
changes should generally be prohibited. ‘
C. Arguments against Liberalism
It might be argued that incommensurability implies not liberalism, but the rejec-
tion of liberalism. The incommensurability thesis asserts that, with respect to some set
of values, no one value is superior to the others as a matter of rational truth, whereas
liberal theory asserts that individual freedom of choice has a special priority over
other values.
In his discussions of Isaiah Berlin’s liberalism, John Gray seems to suggest that it
may be inconsistent to affirm the incommensurability of human values and also assert
that negative freedom has a general priority over other political goods.” Gray notes
that the elevation of choice-making to a central place in the human good cannot be de-
‘0 Incommensurability, in conjunction with some other premise, might imply that lawmakers should
make intuitive estimates of the subjective valuations of every person who will be affected by a par-
ticular type of exchange. But incommensurability does not imply that the result of such intuitive esti-
mates would be a legal system that generally permits free market exchange. To make such an infer-
ence, liberals would have to use some very questionable empirical premises concerning citizens’ ac-
tual subjective valuations and lawmakers’ intuitions.
” See Gray, Berlin, supra note 37 at 97 (raising a question: “If fundamental human values are in-
commensurable, … what can justify according negative freedom even a general priority over other …
political goods?”). See also Gray, Enlightenment’s Wake, supra note 19 at 141 (suggesting that Ber-
lin’s claim that liberty and other values are incommensurable “is not easily reconciled” with his claim
that negative liberty “is to be accorded a general, though never absolute priority over other ultimate
values”).
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383
rived from the thesis of value incommensurability.’ Gray then makes the further as-
sertion that the incommensurability thesis is “incompatible with any claim that free-
dom of choice has universal and pre-eminent value. 3
I agree with Gray that a priority for free choice cannot be derived from the in-
commensurability thesis. The thesis of rational incommensurability merely asserts
that reason does not require or prohibit any particular priority ranking among values,
and thus does not imply any priority for free choice. Yet this does not make a “pre-
eminent7′ priority for free choice “incompatible” with incommensurability. The fact
that thesis B cannot be derived from thesis A does not entail that B is inconsistent
with A. Because no particular priority ranking among incommensurable values is
prohibited by reason, a theorist or a society may, without being inconsistent or irra-
tional, subjectively assign freedom of choice a general priority over other values. A
liberal priority for freedom is therefore not incompatible with the incommensurability
of values.
A liberal claim that free choice has “universal” value is also not incompatible
with the incommensurability thesis. One can maintain that free choice is incommen-
surable with other values and also maintain that free choice is always and everywhere
a value worthy of human aspiration.
An assertion that reason requires that every human society assign a high priority
to individual free choice would be incompatible with rational incommensurability. If
this is the assertion Gray means to deny in the passage quoted above, I would agree
with his denial. But this denial is not a reason to reject liberal theories that do not
claim that a priority for free choice is required by reason. A liberal may claim a prior-
ity for free choice, yet acknowledge that this priority is based on cultural tradition or
intuition and neither required nor prohibited by the rules of rationality.
John Kekes has provided the pieces for an argument that purports to block even
this last liberal claim. Kekes asserts that it is unjustifiable and unreasonable to regard
any value as having absolute, unconditional priority over other values with which it is
rationally incommensurable.’ It is unreasonable to regard any of these values as un-
conditionally overriding the others, because good lives require a balance among a plu-
rality of values.’ Thus, if (1) liberal values, such as individual freedom, are rationally
incommensurable with other important values, and (2) it is unreasonable even subjec-
tively to regard any incommensurable value as unconditionally overriding, then (3) it
is unreasonable to assign any liberal value absolute priority over other values. But,
‘ See Gray, Berlin, ibiL at 161.
Ibid
Kekes, Pluralism, supra note 36 at 202.
‘See ibid at 212-13.
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says Kekes, liberals do regard certain liberal values as having absolute priority.” Lib-
eralism is therefore inconsistent with the conjunction of premise (1), incommensura-
bility, and premise (2), making it unreasonable to regard-even subjectively–one in-
commensurable value as unconditionally overriding another.
The major problem with this argument is that it can imply the rejection of only
those liberal theories that assert that some liberal value has absolute priority. Many
liberals claim a special importance or general priority for individual liberty and other
liberal values but do not claim absolute priority for any such value. Isaiah Berlin, for
example, regarded negative freedom as an especially important value but denied that it
had absolute priority over other values.”
D. Arguments against Absolute Rights and Duties
Does incommensurability imply any answer to the question whether basic or fun-
damental legal rights and their correlative legal duties should be absolute? We will
first consider an argument that incommensurability implies a negative answer.
The Kekesian argument outlined in the previous section might be used, not to re-
fute all liberal theories, but to refute any theory holding that some basic legal rights
and their correlative legal duties should be made absolute. The argument would first
assert that all basic human goods are rationally incommensurable and would then as-
sert that it is unreasonable for lawmakers to regard, even by way of a subjective
judgment that is not claimed to be required by reason, one basic human good as hav-
ing absolute priority over other goods with which it is rationally incommensurable. It
would therefore be unreasonable for lawmakers to assign absolute priority to any ba-
sic human good.
The next steps in the argument apply this conclusion to the realm of legal rights
and duties. A legal right is a legal guarantee against interference with a citizen’s moral
right to enjoy or pursue some basic human good in a certain way. Each such moral
and legal right is guaranteed and protected by a set of legal duties prohibiting state of-
ficials and other citizens from interfering with a citizen’s exercise of this right. A legal
right is tied to, and derives its strength from, a moral right, which in turn is tied to, and
‘6 Ibid. at 202; J. Kekes, Against Liberalism (Ithaca, N.Y: Cornell University Press, 1997) at 171.
See Berlin, Four Essays, supra note 3 at lvi (stating that negative freedom is not absolutely supe-
rior to other ultimate values), 169 (disclaiming any assertion that individual freedom is the sole, or
even dominant, criterion for social action); Berlin, Crooked Timber, supra note 2 at 12-13 (suggesting
that liberty may sometimes have to be curtailed for the sake of other values).
A second problem with Kekes’s argument involves the assertion in his premise (2) that it is un-
reasonable to subjectively recognize absolute priorities between incommensurable values. For argu-
ments against this premise, see supra note 48 and Section D below.
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derives its strength from, some basic human good. If it is unreasonable for lawmakers
to regard that good as having absolute priority over other goods, it would seem unrea-
sonable for lawmakers to regard a citizen’s moral right to pursue that good as having
absolute priority over other citizens’ moral rights to pursue other goods. If it is unrea-
sonable for lawmakers to assign absolute priority to the moral right, it would seem un-
reasonable to assign absolute priority to the legal right derived from it.
We need not accept this argument, because we need not accept the crucial Keke-
sian premise asserting that it would be unreasonable for lawmakers to regard any ba-
sic human good as having absolute priority over other goods with which it is ration-
ally incommensurable. Recall that the reason for this premise was that good lives re-
quire a balance among a plurality of values. We could acknowledge that the well-
being of our fellow citizens generally requires a balance among conflicting goods.
But we could nevertheless assert that there is some basic good (or some aspect of a
basic good) that deserves absolute priority because it is especially vital to human
well-being (at least in our society) and would not destroy the required balance among
goods if it were given absolute priority. If there is such a good or aspect of a good, the
reason for the Kekesian premise falls. A healthy balance among goods does not pre-
clude absolute priority for one good.
Before denying the possibility that there is such a good, we should recognize that
reason cannot require any particular balance among rationally incommensurable
goods. It would thus be difficult for an opponent of absolute rights to maintain that the
required balance would be destroyed by an absolute priority for any good whatsoever.
If absolute priority for a particular good promotes a vital human interest and produces
only infrequent and slight impairments to the realization of other goods, a reasonable
person might well contend that such a priority actually improves the balance among
goods.
E. Arguments for Absolute Rights and Duties
John Finnis maintains that there are absolute human rights, for example, the right
not to be killed as a means to some further end and the right not to be deprived of
one’s procreative capacity.’ Finnis argues that these absolute rights are correlative to
the absolute duties entailed by the moral principle prohibiting lawmakers and citizens
from intentionally and directly destroying, damaging, or impeding any instantiation of
a basic human good in order to indirectly bring about some other instantiation of a ba-
sic human good.’
See Finnis, Natural Law, supra note 30 at 225.
See ibid. at 118-21 (asserting that the strict inviolability of basic human rights rests on the re-
quirement that one should not choose to directly impair an instantiation of one or more basic human
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According to Finnis, the rationality of these absolute moral duties and the legal
norms drawn from them “depends upon the incommensurability of the human goods
and bads at stake in morally significant options for choice.'” Finnis tries to explain
how the duties to refrain from directly impairing instantiations of basic goods depend
upon the rational incommensurability of the instantiations that would be impaired and
the alternative instantiations that might be realized by means of this impairment:
[UInstantiations of human good constitute reasons against any option which in-
volves choosing (intending) to destroy or damage any of them. The signifi-
cance of the incommensurability of goods involved in such morally significant
options is that no reasonfor such an option can be rationally preferable to such
a reason against.”
It is difficult to follow Finnis’s inference and see how the incommensurability of
alternative instantiations implies a principle that instantiations of good must never be
harmed in order to bring about other instantiations. If instantiation B could only be
goods), 225 (stating that absolute rights are correlative to the exceptionless duties entailed by the re-
quirement to never choose directly against any basic value). See also Finnis, “Commensuration”, su-
pra note 10 at 226 (stating that the principle that evil may not be done for the sake of good (the prin-
ciple prohibiting the harming of an instantiation of a basic good as a means of bringing about some
other instantiation of a basic good) is the foundation of absolute human rights); Finnis, “Legal Rea-
soning”, supra note 58 at 147-48 (asserting that the moral absolutes imposed by the moral principle
prohibiting choosing to destroy or damage any basic human good in any of its instantiations in any
human person constitute basic human rights).
Finnis, “Legal Reasoning”, ibid. at 148.
91 Ibid. at 147 [emphasis in original]. Elsewhere in the same essay, Finnis provides the same
explanation:
A basic human good always is a reason for action and always gives a reason not to
choose to destroy, damage, or impede some instantiation of that good; but since the in-
stantiations of human good at stake in any morally significant choice are not commen-
surable by reason prior to choice, there can never be a sufficient reason not to take that
reason-not-to as decisive for choice.
Ibid. at 138 [emphasis in original]. See also J. Finnis, Moral Absolutes (Washington, D.C.: Catholic
University of America Press, 1991) at 54-55 (arguing that because basic goods are rationally incom-
mensurable, there can be no rationally preferable reason for destroying, damaging, or blocking a basic
good in order to realize a basic good); J. Finnis, Natural Law and Natural Rights (Oxford: Clarendon
Press, 1980) at 120 (arguing that directly damaging an instantiation of a basic good in order to indi-
rectly promote some other instantiation of a good is to treat the instantiations as commensurable);
Finnis, “Commensuration”, supra note 10 at 226 (arguing that promoting an instantiation of a good as
an end (E) cannot be a reason to impair an instantiation of a good as a means (M) unless E and M
could be commensurated and E rationally judged to be the greater good, which is impossible).
A similar argument from incommensurability is made in George, “Moral Judgments”, supra note
20 at 192 (arguing that the incommensurability thesis entails that one cannot have conclusive reasons
for choosing to damage or destroy a basic good in any of its instantiations in order to bring about in-
stantiations of another basic good).
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H.S. MATHER – LAW-MAKING AND INCOMMENSURABILITY
produced by destroying instantiation A, and A and B are rationally incommensurable
as teleological ends, neither A nor B is rationally superior to the other as instantiations
of good. As Finnis suggests, B is not rationally preferable to A. But neither is A ra-
tionally preferable to B. Reason seems to leave the agent free either to protect A or
promote B by destroying A. Obviously, incommensurability by itself does not imply
that A must be protected and not harmed. Finnis needs an additional premise.
Finnis’s other premise might be a moral principle providing that we should never
choose an option that directly harms any instantiation of a basic good, unless such a
choice is required by reason. With this premise, Finnis can reason as follows:
(1) An instantiation of a basic good must never be directly destroyed, damaged, or
impeded in order to produce some alternative instantiation, unless this is required by
reason;
(2) Alternative instantiations of basic goods are always rationally incommensura-
ble (neither is required by reason); therefore,
(3) An instantiation of a basic good must never be directly destroyed, damaged, or
impeded in order to produce some alternative instantiation.
Should we accept the first premise?’ Why not accept a contrary premise that
sometimes allows us to impair an instantiation of good in order to bring about some
other (admittedly rationally incommensurable) instantiation that we (subjectively)
value more highly? Is avoiding harm always more important than doing good?
Finnis suggests, in answer to these questions, that an absolute duty to promote
good whenever there is an opportunity to do so could not possibly be complied with,
whereas an absolute duty to refrain from harming good can always be adhered to and
leaves open a wider field of choice’ But must we choose between two absolute du-
ties? Lawmakers could recognize a conditional duty to avoid harming any instantia-
tion of good, a duty that would sometimes permit them, for example, to directly de-
prive a citizen of recreational play for a short time in order to enable other citizens to
realize instantiations of other basic goods.’
Finnis has not shown why lawmakers should accept a premise absolutely prohib-
iting them from directly impairing an instantiation of good in order to promote an-
other instantiation whenever such an impairment is not required by reason. Without
92This question has been raised by David J. Luban in “Incommensurable Values, Rational Choice,
and Moral Absolutes” (1990) 38 Clev. St. L. Rev. 65 at 79, 81 (questioning why the reason against an
option should prevail over the reason for that option, when neither reason is rationally stronger than
the other).
93 See Finnis, “Legal Reasoning”, supra note 58 at 147-48.
9′ Finis regards play as one of the basic human goods. See Finnis, Natural Law, supra note 30 at 87.
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such a premise, the incommensurability thesis does not lead to the conclusion that
lawmakers have an absolute duty not to directly destroy, damage, or impair any in-
stantiation of a basic human good in order to bring about some other instantiation.
Without such an absolute duty, Finnis’s argument for absolute rights collapses.
Conclusion
For jurisprudential purposes, value incommensurability can be defined as the ab-
sence of rational commensurability, either metrical or ordinal. Values are rationally
incommensurable if the generally accepted rules of rationality do not require a judg-
ment that one value is superior to the other(s) or that the values are precisely or
roughly equal. This article has focused on basic human goods and their instantiations.
I have suggested that abstract basic human goods are usually, if not always, rationally
incommensurable and that instantiations of such goods are often, though not always,
rationally incommensurable.
When confronted with conflicting goods or instantiations that are rationally in-
commensurable, lawmakers can make choices that are not irrational. They can use
intuition to make arational choices not prohibited by reason. They can use moral prin-
ciples, social traditions, and prudential principles to make rational choices. These ara-
tional or rational choices will be neither required by reason nor prohibited by reason.
We have considered a number of arguments claiming that incommensurability
implies some particular substantive position in jurisprudential theory: the rejection of
consequentialism, the adoption of liberalism, the rejection of liberalism, the rejection
of absolute legal rights and duties, or the moral necessity for absolute rights and du-
ties. All such arguments should be rejected. The incommensurability thesis merely as-
serts that rational persons can disagree as to how certain conflicts between goods or
instantiations should be resolved. It does not tell lawmakers which rationally permis-
sible resolution they should prefer.
Although philosophical reflection on incommensurability may not enable us to
solve any substantive problem in jurisprudence, such reflection is still worthwhile. It
can remind us of the limits of human reason and serve as an antidote to dogmatism. It
can teach us intellectual and moral humility, philosophy’s greatest lesson and one we
sorely need.
