Jerry Fodor - Intentional Realism - Productivity, Systematicity and Thought

Productivity, Systematicity and Thought

Fodor also has positive arguments in favour of the reality of mental representations in terms of the LOT. He maintains that if language is the expression of thoughts and language is systematic, then thoughts must also be systematic. Fodor draws on the work of Noam Chomsky to both model his theory of the mind and to refute alternative architectures such as connectionism. Systematicity in natural languages was explained by Chomsky in terms of two more basic concepts: productivity and compositionality.

Productivity refers to a representational system's unbounded ability to generate new representations from a given set of symbols. "John", "loves", and "Mary" allow for the construction of the sentences "John loves Mary" and "Mary loves John". Fodor's language of thought theorizes that representations are decomposable into constituent parts, and these decomposed representations are built into new strings.

More important than productivity is systematicity since it does not rely on questionable idealizations about human cognition. The argument states that a cognizer is able to understand some sentence in virtue of understanding another. For example, no one who understands "John loves Mary" is unable to understand "Mary loves John", and no one who understands "P and Q" is unable to understand "P". Systematicity itself is rarely challenged as a property of natural languages and logics, but some challenge that thought is systematic in the same way languages are. Still others from the connectionist tradition have tried to build non-classical networks that can account for the apparent systematicity of language.

The fact that systematicity and productivity depend on the compositional structure of language means that language has a combinatorial semantics. If thought also has such a combinatorial semantics, then there must be a language of thought.

The second argument that Fodor provides in favour of representational realism involves the processes of thought. This argument touches on the relation between the representational theory of mind and models of its architecture. If the sentences of Mentalese require unique processes of elaboration then they require a computational mechanism of a certain type. The syntactic notion of mental representations goes hand in hand with the idea that mental processes are calculations which act only on the form of the symbols which they elaborate. And this is the computational theory of the mind. Consequently, the defence of a model of architecture based on classic artificial intelligence passes inevitably through a defence of the reality of mental representations.

For Fodor, this formal notion of thought processes also has the advantage of highlighting the parallels between the causal role of symbols and the contents which they express. In his view, syntax plays the role of mediation between the causal role of the symbols and their contents. The semantic relations between symbols can be "imitated" by their syntactic relations. The inferential relations which connect the contents of two symbols can be imitated by the formal syntax rules which regulate the derivation of one symbol from another.