Values, such as liberty and equality, are sometimes said to be incommensurable in the sense that their value cannot be reduced to a common measure. The possibility of value incommensurability is thought to raise deep questions about practical reason and rational choice as well as related questions concerning topics as diverse as akrasia, moral dilemmas, the plausibility of utilitarianism, and the foundations of liberalism. This entry outlines answers in the contemporary literature to these questions, starting with questions about the nature and possibility of value incommensurability.2. Incomparability
2.1 Vagueness
2.2 “Roughly Equal” and “On a Par”
3. Arguments for Value Incommensurability
3.1 Does Incomparability Imply Incommensurability?
3.2 Constitutive Incommensurability
3.3 Moral Dilemmas
3.4 Akrasia
4. Deliberation and Choice
4.1 Optimization and Maximization
4.2 Cyclical Choice
4.3 Rational Eligibility
4.4 External Resources
4.5 Non-Maximizing Choice
4.6 Deliberation about Ends
5. Social Choices and Institutions
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[size=30]1. Value Incommensurability
Incommensurability between values must be distinguished from the kind of incommensurability associated with Paul Feyerabend (1978, 1981, 1993) and Thomas Kuhn (1977, 1983, 1996) in epistemology and the philosophy of science. Feyerabend and Kuhn were concerned with incommensurability between rival theories or paradigms — that is, the inability to express or comprehend one conceptual scheme, such as Aristotelian physics, in terms of another, such as Newtonian physics.
In contrast, contemporary inquiry into value incommensurability concerns comparisons among abstract values (such as liberty or equality) or particular bearers of value (such as a certain institution or its effects on liberty or equality). The term “bearer of value” is to be understood broadly. Bearers of value can be objects of potential choice (such as a career) or states of affairs that cannot be chosen (such as a beautiful sunset). Such bearers of value are valuable in virtue of the abstract value or values they instantiate or display (so, for example, an institution might be valuable in virtue of the liberty or equality that it engenders or embodies).
1.1 Measurement and Comparison
The term “incommensurable” suggests the lack of a common measure. This idea has its historical roots in mathematics. For the ancient Greeks, who had not recognized irrational numbers, the dimensions of certain mathematical objects were found to lack a common unit of measurement. Consider the side and the diagonal of a square. These can be compared or ranked ordinally, since the diagonal is longer. However, without the use of irrational numbers, there is no way to specify with cardinal numbers exactly how much longer the diagonal is than the side of a square. The significance of this kind of incommensurability, especially for the Pythagoreans, is a matter of some debate (Burkert 1972, 455-465). Hippasus of Metapontum, who was thought by many to have demonstrated this kind of incommensurability, is held by legend to have been drowned by the gods for revealing his discovery (Heath 1921, 154; von Fritz 1970, 407).
Given these historical roots, some authors reserve the term “incommensurable” for comparisons that can be made, but not cardinally (Stocker 1980, 176; Stocker 1997, 203) or not precisely (Chang 1997b, 2). Others interpret the idea of a common measure more broadly. On this broader interpretation, for there to be a common measure, all that is required is that ordinal comparisons or rankings are possible. Values are then incommensurable only when not even an ordinal comparison or ranking is possible. Unless stated otherwise, this entry adopts this latter interpretation.
1.2 Incommensurable or Incomparable?
Because the idea of comparison is closely tied to the topic of value incommensurability, this has led to use of the term “incomparable” alongside “incommensurable” in the literature. Some authors use the terms interchangeably (e.g., Raz 1986). Others use them to refer to distinct concepts (e.g., Chang 1997b). This entry distinguishes between the two concepts in the following manner.
Joseph Raz defines two bearers of value as incommensurable if it is false that of the two “either one is better than the other or they are of equal value” (1986, 342). Raz offers an example in which a person faces the choice between two equally successful careers: one as a lawyer and one as a clarinetist. Neither career seems better than the other, and they also do not appear to be equally good. If they were of equal value, then a slightly improved version of the legal career would be better than the musical career, but this judgment appears incorrect. The legal career and the musical career, according to Raz, are incommensurable.
Ruth Chang has proposed use of the term “incomparable” to describe the legal career and the musical career (1997b, 4). Two bearers of value are held to be incomparable if no positive comparative judgment of their value is true. Positive comparative judgments of value specify the way in which two items compare (e.g., “better than”) rather than the way in which two items do not compare (e.g., “not better than”) in virtue of some value.
Drawing on Chang’s proposal, this entry uses the term “incomparable” ordinarily to describe two or more concrete bearers of value of which no positive comparative evaluative judgment is true. In contrast, this entry uses the term “incommensurable” to describe the way in which two or more abstract values stand in relation to one another. Subsection 3.1 considers in greater detail the relationship between the incomparability of bearers of value and the incommensurability of values. The remainder of section 1 considers ways in which to conceive of incommensurable values.
1.3 Conceptions of Value Incommensurability
This section outlines three conceptions of value incommensurability, each one capturing some sense in which incommensurable values lack a common measure.
The first conception characterizes value incommensurability in terms of restrictions on how the further realization of one value outranks realization of another value. James Griffin has proposed forms of value incommensurability of this sort. One form involves what he calls “trumping.” In a conflict between values
A and
B,
A is said to trump
B if “
any amount of
A, no matter how small, is more valuable than
any amount of
B, no matter how large” (Griffin 1986, 83). A weaker form of value incommensurability involves what Griffin calls “discontinuity.” Two values,
A and
B, are incommensurable in this sense if “so long as we have enough of
B any amount of
A outranks any further amount of
B; or that enough of
A outranks any amount of
B” (Griffin 1986, 85).
If values are incommensurable in this first sense, there is no ambiguity whether the realization of one value outranks realization of the other. Ambiguity as to whether the realization of one value outranks realization of the other, however, is thought by many theorists to be a central feature of incommensurable values. The second and third conceptions of value incommensurability aim to capture this feature.
According to the second conception, values are incommensurable if and only if there is no true general overall ranking of the realization of one value against the realization of the other value. David Wiggins, for example, puts this forward as one conception of value incommensurability. He writes that two values are incommensurable if “there is no general way in which A and B trade off in the whole range of situations of choice and comparison in which they figure” (1997, 59).
This second conception of value incommensurability denies what Henry Richardson calls “strong commensurability” (1994, 104-105). Strong commensurability is the thesis that there is a true ranking of the realization of one value against the realization of the other value in terms of one common value across all conflicts of value. A denial of such a singular common value, however, does not rule out what Richardson calls “weak commensurability” (1994, 105). Weak commensurability is the thesis that in any given conflict of values, there is a true ranking of the realization of one value against the realization of the other value in terms of some value. This value may be one of the values in question or some independent value. This value also may differ across value conflicts. The denial of strong commensurability does not entail a denial of weak commensurability. Even if there is no systematic or general way to resolve any given conflict of values, there may be some value in virtue of which the realization of one value ranks against realization of the other. Donald Regan defends the thesis of strong commensurability (Regan 1997). Depending on how the relationship between value incommensurability and incomparability is construed (subsection 3.1), Ruth Chang could be considered a defender of weak commensurability. She argues that “nameless values” combine values in a way that allows for the comparability of alternatives in virtue of these nameless values (Chang 2004).
The third conception of value incommensurability denies both strong and weak commensurability (Richardson 1994, Wiggins 1997, Williams 1981). This conception claims that in some conflicts of values, there is no true ranking of values.
This third conception of value incommensurability is sometimes said to be necessary to explain why, in conflicts of value, a gain in one value does not always cancel the loss in another value. This view assumes that, whenever there is a true ranking between the realization of one value and the realization of another value, the gain in one of the values cancels the loss in the other. Many commentators question that assumption. This entry leaves open the possibility that when there is a true ranking between the realization of one value and the realization of another value, the gain in one of the two values need not cancel the loss in the other.
If we accept this possibility, a number of questions arise. One question is what a ranking of realizations of values means if a gain in one value does not cancel the loss in the other. A second question is whether the first and second conceptions of value incommensurability each admit of two versions: one version in which the gain in one value cancels the loss of the other and one version in which it does not. A third question concerns the relation between value incommensurability and tragedy. It may be thought that what makes a choice tragic is that, no matter which alternative is chosen, the gain in value cannot cancel the loss in the other value. Not all authors, however, regard all value conflicts involving incommensurable values as tragic (Richardson 1994, 117). Wiggins, for example, reserves the second conception of value incommensurability for what he calls “common or garden variety incommensurable” choices and the third conception for what he calls “circumstantially cum tragically incommensurable” choices (1997, 64).[/size]
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