Abstract

According to Chomsky, the ability to speak and understand a language rests in part on knowledge of complex and abstract grammatical rules. This knowledge is used, when a person speaks or understands a sentence, to generate structural descriptions, analogous to those devised by linguists, at an unconscious level of the speaker's or hearer's mind. Speaking and understanding thus involve complex, mental activity akin to translation. Chomsky holds that this activity should be thought of as processes in the brain. ;I argue that this picture implies an explanatory regress. Structural descriptions are sentence-like objects with grammatical structure which therefore present the same problem of understanding as ordinary sentences in a public language. This kind of problem is thought by many writers in the philosophy of mind and cognitive psychology to be avoided by appeal to a functional theory of mind, or an analogy with the operations of a computer. ;Functionalism, the dominant version of physicalism in philosophy of mind, assumes that behaviour and perception can be thought of in physical terms, as bodily movement and the stimulation of sense organs--'input' and 'output'. I argue that this is a confusion, and therefore the functionalist analysis of mental phenomena does not explain the supposed identity of brain processes and mental states and events. ;The idea of computational psychology, that mental phenomena consist in physical states and processes like those which take place in computers, assumes that brain processes can be described in syntactic terms, or as symbol-processing. But the description of computers in these terms is relative to norms of operation set by designers, programmers and users. There is no such normative context for human brains, so they cannot properly be described in computational terms. ;The incoherence of functionalism and the computational theory of mind leaves Chomsky's interpretational, intellectualist model of language understanding without a defence to the problem of regress. The hypothesis of knowledge of grammar is therefore not an explanation of the ability to understand and speak a language, and is unmotivated