In defense of his Language of Thought Hypothesis (SEP article), Jerry Fodor argues that Thought is recursively compositional in just the same way that Language is. When we understand a sentence, we invoke a representational token that corresponds to the proposition the sentence expresses, and this token is itself broken down into different cognitive representational parts according to the same logical form as that of the sentence. So it's all very Russellian in spirit.

In theories of Truth, it's not always taken for granted that our languages of interest are compositional in the way that Russell's Principia Mathematica language was. Stephen Yablo's Groundedness interpretation of Kripke's theory (e.g. Truth and Reflection ('85)) implies that sentences can't universally be simply broken down into parts in a properly stable semantic evaluation. In some such theories of truth, the Liar sentence L: (L <-> ¬T([L])) emerges as semantically sensible, but given a non-standard truth value, yet, for example, T(L) v ¬T(L) must also be standardly true.

There seems to be some intuitive pull to the idea of recursive compositionality in logical Truth, and I'm interested in this from a constructive mathematics perspective. I'm philosophically curious to cash out and critique that intuition by wondering about the reverse implication to Fodor's: whether if thought is recursively compositional, thus language. I have a particular concern in mind (does Fodor present any argument for what use he makes of strictly finite or computable methods in his view of the mind), but all the questions below seem interesting.

  1. Is Fodor's general project (or Functionalism in general) known to be challenged by derivations like the Liar sentence, Godel sentences or Turing halting problems as features of natural or grammatical language, and does he address this anywhere in his work?
  2. Does Fodor have a particular preference for strictly finitistic or classical theories of logical consequence or inference that would prohibit Liar-style sentences or non-compositional features? Does he explore or argue for this at any point in his work?
  3. If Fodor thinks that language and thought both follow a Tarski-style logical form, and given Tarski's own theorem about the undefinability of Truth for metalanguage in object language due to the Liar paradox, does this make meta-theory (e.g. mathematical computation or complexity theory) impossible for Fodorian minds? Why/not?

For non-Fodorians, I would also be interested in how other computational theories of mental representation might respond to the above questions!

1 Answer 1


By thought, one has to be clear exactly what is meant by this; in the linked SEP entry, they write:

LOTH is an hypothesis about the nature of thought and thinking with propositional content. As such, it may or may not be applicable to other aspects of mental life. Officially, it is silent about the nature of some mental phenomena such as experience, qualia, sensory processes, mental images, visual and auditory imagination, sensory memory, perceptual pattern-recognition capacities, dreaming, hallucinating,etc

The important thing here is propositional content. But the entry goes on to say:

To be sure, many LOT theorists hold views about these aspects of mental life that sometimes make it seem that they are also to be explained by something similar to LOTH

I would dispute that human thought is propositional. What appears propositional is thought in its public aspect - language. But in itself, even when its public form is propositional, its private form is not. Wittgenstein wrote in his Philosophical Investigations, that:

"comprehending a proposition means comprehending a language."

I suspect thought in itself is much closer to experience, qualia and revelation. I use the word revelation, as in the minor mode of ephiphanies, when we understand something that we had not understood before (rather than in its major mode, as in islamic or buddhist theology).

I suspect further, that our experience of language is synthetic, and when we think 'in words', what we are doing in fact is simulating the public enunciation within our thoughts, they're not our thoughts themselves.

The idea that there is a simple one-to-one mapping of units of meaning of a sentence and thoughts seem to me wrong-headed. However I do think that we are cognitively 'preprogrammed' to understand language - Chomskys deep grammar - and that there is a probable mapping onto this from language.

(One, notably could invert this, and say that it is because of deep grammar language has the structure that it does).

I'd see this in the same way that certain structures in the retina encode for straight line, colour, contrast etc. But one wouldn't mistake this for vision or 'what I see', which is synthetically whole.

Further, I'd be against the analytic understanding of thought, in its semantic aspect; rather than syntactical, which is only the form of language, that is the form of public thought. Before we can understand a word, we must understand the world; or as Quine put it:

"the unit of measure of empirical meaning is all of science in its globality".

  • Could I maybe ask you to say a little more about Chomsky's deep grammar idea, and why we might want to think there's some cognitive pre-programming going on? I hadn't thought about that as a line of argument on this, but now that you mention it, it seems absolutely relevant. Is there a particular book or paper where Chomsky specifically defends a non-linguistic cognitive grammar, over defending the (probably more well-formed) cognitive thesis that the human brain is highly adapted to thinking grammatically?
    – Paul Ross
    Sep 23, 2013 at 21:44
  • I'm afraid I can't be much more specific than that - I picked up the idea some twenty years ago and I haven't looked into it since. It does look like though I've been careless in my terminology though, my cognitive pre-programming is your adaptation to thinking gramatically. Sep 24, 2013 at 16:20

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