Chomsky, Noam (1928–)

3. Indeterminacy and underdetermination

Knowledge of language, Chomsky has argued, presents a strong argument in favour of traditional rationalist approaches to mind and against traditional empiricist approaches (see Learning §1; Rationalism). In particular, ‘learning’ is treated as more akin to growth and the course of acquisition is seen more as the unfolding of innate propensities under the trigger of experiential input than as the result of the shaping effects of the environment. This rationalist perspective is now quite common and this is largely due to Chomsky’s efforts. Chomsky has consistently warned against empiricist prejudices in philosophy, and in no instance more strongly than in his critique of Quine’s methodological remarks on linguistics (for example, see Quine 1960).

Chomsky takes Quine to be arguing that linguistic investigations are beset with problems greater than those endemic to inquiry in general. Whereas empirical investigation in general suffers from underdetermination of theory by evidence, linguistic study is beset with the added problem of indeterminacy (see Radical translation and radical interpretation §§2–3). Indeterminacy differs from standard inductive underdetermination (see Underdetermination) in that where there is indeterminacy ‘there is no real question of right choice’ among competing proposals. Chomsky interprets Quine as arguing that ‘determining truth in the study of language differs from the problem of determining truth in the study of physics’ (Chomsky 1975: 182–3).

In reply, Chomsky (1969) argues that Quine’s thesis rests on classical empiricist assumptions about how languages are acquired. Quine, he argues, supposes that humans have ‘an innate quality space with a built-in distance measure’ tuned to certain ’simple physical correlates’. In addition, certain kinds of induction in this space are permitted. Beyond this, however, ‘language-learning is a matter of association of sentences to one another and to certain stimuli through conditioning’. Further, one cannot ‘make significant generalizations about language or common-sense theories, and the child has no concept of language or of “common-sense” prior to this training’ (Chomsky 1969: 54–5, 63).

Chomsky notes that Quine provides no evidence to support these assumptions. Nor can there be any good evidence to support them if the nature of the learning problem in the domain of language is characterized as Chomsky has argued it must be. Chomsky concludes that ‘Quine’s thesis of the indeterminacy of translation amounts to an implausible and quite unsubstantiated empirical claim about what the mind brings to the problem of acquisition of language (or of knowledge in general) as an innate property’ (Chomsky 1969: 66). Stripped of these tendentious empirical assumptions, Quine fails to show that indeterminacy is anything other than the familiar problem of underdetermination of theory by evidence as applied to linguistics. Chomsky (1996) has since argued that the ultimate source of many critiques of the mental sciences in general and linguistics in particular (including Quine’s indeterminacy thesis) is a kind of methodological dualism that takes humans to be separate from the natural world. This dualism is manifest in the a priori constraints that philosophers place on explanations in the mental sciences, which would be regarded as inappropriate if applied to the physical sciences.

In this vein Chomsky asks, for example, why access to consciousness is so often taken to be crucial in substantiating the claim that humans have I-language or follow rules. Suppose, he asks, we had a theory that perfectly described what happens when sound waves hit the ear, stimulating the performance system to access the cognitive system and construct a logical form that interacts with other cognitive systems to yield comprehension, in so far as the language faculty enters into this process. What more could be desired? The insistence that this entire process be accessible to consciousness in order for the account to be credible, he argues, is a demand beyond naturalism, a form of methodological dualism of dubious standing that would be summarily rejected if raised elsewhere.

Or consider the oft-voiced suspicions concerning mentalist approaches in psychology. Many philosophers are ready to accept these as perhaps temporarily necessary but ultimately, the view seems to be, mentalist theories must reduce to physical ones to be truly legitimate. Chomsky argues that this sentiment is another manifestation of methodological dualism and should be rejected. First, it presupposes that there is a tenable distinction between the mental and the physical. However, Chomsky argues that since Newton undermined the Cartesian theory of body by showing that more ‘occult’ forces were required in an adequate physics, mind–body dualism has lost all grounding. Second, even if reduction were possible, reduction comes in many varieties and there is little reason to believe that the contours of the reducing physical theory would be left unaffected by the process. Since Newton, Chomsky notes, ‘physical’ has been an honorific term that signifies those areas in which we have some nontrivial degree of theoretical understanding. The relevant scientific question is whether some theory or other offers interesting descriptions and explanations. The further insistence that its primitives be couched in physical vocabulary is either vacuous (because ‘physical’ has no general connotation) or illegitimate (another instance of methodological dualism).

The general conclusion Chomsky draws is that whatever problems linguistic theory encounters, it is no more methodologically problematic than theories in other domains. He attributes the qualms of philosophers to lingering empiricist dogma or an indefensible epistemological dualism.