The Language of Thought : Part I Joe Lau Philosophy HKU

Readings Ned Block’s “The Mind as the Software of the Brain” Murat Aydede “The LOT Hypothesis” at Ch. 10 “The Language of Thought” in Braddon-Mitchell and Jackson's Philosophy of Mind and Cognition. Fodor and Pylyshyn’s article.

Two types of mental states Intentional vs. Phenomenal Intentional = aboutness, with content/meaning – E.g. beliefs, knowledge, desires Phenomenal = qualitative (“what-is-it-like- ness”, qualia) – E.g. pain, itches, sensations Might have both features – E.g. perception, imagination

The Language of Thought Hypothesis LOT : Intentional mental states - – Linguistic mental representations – Possess a combinatorial syntax and semantics Complex representations built from atomic ones. Meanings of complex representations depend on menaings of the atomic ones and the syntax.

LOT says nothing about : Whether LOT is NL. Whether LOT is innate or learnt. Whether all humans, or all thinkers, have the same LOT. The material basis of LOT.

Why think that LOT is plausible? 1. Explains mind-body interaction. 2. Explains the productivity and systematicity of thoughts. 3. Explains the opacity of thoughts. 4. Explains inferential reasoning.

Mind-body interaction Intentional mental states can causally interact with perception, behaviour and other mental states. Example : visual experience causes belief, belief causes action Explanation : Intentional mental states are mental representations in the brain. Being physical states they can interact with our sensory organs and motor systems and other physical mental representations.

Productivity Productivity : The number of thoughts a human being can entertain is practically infinite. Explanation : A finite number of atomic mental representations can combine with one another in different ways to generate a huge number of complex mental representations.

Systematicity Systematicity : the thoughts we can entertain are all systematicaly related in content. – Example : Evans’ Generality Constraint - if a thinker can think a is F, and b is G, then he must be able to think a is G, and b is F. Explanation : the atomic representations that constitute thoughts must be able to recombine to form thoughts which have distinct but semantically related contents.

Opacity Opacity : The thought that a is F is distinct from the thought that b is F, even if a=b. – Example : One can believe that superman can fly without believing that Clark Kent can fly, even though Clark Kent is Superman. Explanation : There can be distinct mental representations that refer to the same thing, and which have different conceptual roles.

Inferential Reasoning It seems that there are rule-like regularities in reasoning. Examples : – Normally we do not believe in contradictions (P and not-P). – If we are aware that if P then Q and P, then we would normally believe Q (modus ponens). Explanation : Reasoning consists in formal operations on structured mental representations according to their form.

Some Objections from Dennett See Block’s paper

Evaluating the Hypothesis How to evaluate scientific hypothesis? Inference to the best explanation. – What is the best? – Evidence, predictions, consistency, simplicity Any alternative explanations?

An Alternative : The Map Theory Proposal : Intentional mental states are map-like and not language-like. See Braddon-Mitchell and Jackson for further discussion. The map theory can also explain mind-body causal interaction, systematicity, productivity, opacity. What about: – Inferential reasoning – Abstract concepts in logic or mathematics – Disjunctive or conjunctive beliefs Special representations are needed, but then how is it different from LOT?