What is the difference between Jerry Fodor's LOT and Wittgenstein's Picture Theory of Meaning?

Question

From Wikipedia: "[The] the language of thought hypothesis (LOTH) put forward by American philosopher Jerry Fodor describes thoughts as represented in a "language" (sometimes known as mentalese) that allows complex thoughts to be built up by combining simpler thoughts in various ways. In its most basic form, the theory states that thought follows the same rules as language: thought has syntax."

This strikes me as almost identical to Wittgenstein's picture theory of language: That language corresponds to propositions, which in turn correspond to states of affairs built up of atomic facts. These relationship between states of affairs mirrors reality and that is how language and thought mirror the world.

What is the difference between the two concepts?

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Ram Tobolski's answer seems to stand on its own and resolve the question. But I came across this quote from Daniel Dennett's "Kinds of Minds": This problem comes into sharper focus if we contrast the language of thought hypothesis with its ancestor and chief rival, the picture theory of ideas.

So Dennett claims that LOTH is descended from, but different than, the picture theory of ideas. If Dennett is correct, Ram's answer that the two theories addresses compleltely different questions doesn't hold. The two theories do address the same or similar issues.

So my question becomes:

• What are the similarities and what are the differences between the two theories?
• How did the LOTH hypothesis evolve from the picture theory of ideas?

Answer 1

The Early Wittgenstein and Fodor do share the general view that language is representing ("mirroing") its meaning. But otherwise their projects are very different. Fodor's LOTH is a high-order theory in cognitive psychology. It pertains to how the mind works, in accordance with current psychological theories and models. Wittgenstein's Tractatus contains a philosophical theory concerning how meaning and world must be structured from the standpoint of a logically perfect language. Wittgenstein did not deal with psychology or mind. Here is how Bertrand Russell put it, in his Introduction to Wittgenstein's Tractatus :

In order to understand Mr Wittgenstein’s book, it is necessary to realize what is the problem with which he is concerned. In the part of his theory which deals with Symbolism he is concerned with the conditions which would have to be fulfilled by a logically perfect language. There are various problems as regards language. First, there is the problem what actually occurs in our minds when we use language with the intention of meaning something by it; this problem belongs to psychology. Secondly, there is the problem as to what is the relation subsisting between thoughts, words, or sentences, and that which they refer to or mean; this problem belongs to epistemology. Thirdly, there is the problem of using sentences so as to convey truth rather that falsehood; this belongs to the special sciences dealing with the subject-matter of the sentences in question. Fourthly, there is the question: what relation must one fact (such as a sentence) have to another in order to be capable of being a symbol for that other? This last is a logical question, and is the one with which Mr Wittgenstein is concerned. He is concerned with the conditions for accurate Symbolism, i.e. for Symbolism in which a sentence ‘means’ something quite definite.

Fodor's LOTH relates to Russell's first and second problems. Wittgenstein's Tractatus relates to the fourth.

Answer 2

• Wittgenstein's Picture Theory of Meaning was an attempt to explain how language represents the world. His suggestion was pretty much that it works by being isomorphic to the world, in some way or another: parts of sentences map onto parts of the world, and relations between those parts map onto relations between parts of the world. (It's plausible that this is how pictures represent. Suppose I have an illustration of the solar system. This blue blob maps corresponds to Earth, this red blob corresponds to Mars, this big yellow blog corresponds to the Sun, etc.) It's intended, I think, as a metaphysical theory of how representations in general are possible, including language.
• Fodor's Language of Thought Hypothesis is an attempt to describe how human thought is structured. His suggestion is that it is specifically language-like. That is, it is language-like even in ways that pictures and other kinds of representation aren't.

I'll try to get at what's specific to the LOT hypothesis. Fodor's own explanation can be found in his essay Why There Still Has to be a Language of Thought.

Fodor is an intentional realist. Intentional realists think that intentional states ("believes that __", "hopes that __", and whatever else) literally and concretely exist. For someone to be in a particular intentional state, is to have a literal thing in their head that stands for a proposition, and for them to be in an appropriate relation to that thing.

Fodor shares a colourful metaphor that he got from Stephen Schiffer. Inside my head there is a thing, let's say it's a pebble, which somehow has come to represent the proposition that "The soup has gotten cold". I also have a bunch of boxes in my head, which the pebble can go in. If I believe that the soup has gotten cold, then the pebble is in my "belief box". If I hope that the soup has gotten cold, then the pebble is in my "hope box". If I fear that... etc.

(And if I believe that the dog bit the man, then a different pebble is in my belief box.)

So far that's just intentional realism. The LOT hypothesis is specific about what the things, the representations, have to be like. In LOT, they can't be pebbles.

If LOT is false, it might be the case that there is a representation for "Bob loves Jill", and a different representation for "Jill loves Bob", but also for the two representations to have nothing to do with each other. They might be two pebbles (no more similar to each other than either one is to the pebble representing "It was the best of times, it was the worst of times..."). It might be possible to have an animal capable of having the thought that Bob loves Jill, but incapable of having the thought that Jill loves Bob (since it has one of the pebbles but not the other one).

LOT says that representations of propositions have constituent structure. That is, the "Bob loves Jill" representation is made of parts; and furthermore, those are the same parts that the representation "Jill loves Bob" is made of. That's why it's absurd to imagine someone understanding the first sentence but not the second. If you have the constituents, then you can understand strings which are put together out of those constituents.