There has been a bit of a kerfuffle in the thread to What’s Chomsky Thinking Now concerning Fodor’s claim that all of our concepts are innate. Unfortunately, with the exception of Alex Drummond, most who have participated in the discussion appear unacquainted with Fodor’s argument. It has two parts, both of which are interesting. To help focus the indignation of his critics, I will outline them below as a public service. Before starting however, let me share with you my own personal rule of thumb in these matters, one that I learned from Kuhn’s discussions of Aristotelian physics: when someone very smart says something that you think is obviously dumb then go back and reread it for it may be that you have thoroughly misunderstood the point. I am acquainted with Jerry Fodor. Let me assure you he is very smart. So let’s start.
As noted Fodor has a two pronged argument. The first part (an excellent very short form of which can be found here 143ff) is an observation about learning as a form of inductive logic. Fodor distinguishes between theories of concept acquisition and theories of belief fixation. The latter is what theories of learning are about. Learning theories have nothing general to say about concept acquisition because, being inductive theories, they presuppose the availability of a set of basic concepts without which the inductive learning mechanism cannot get off the ground. If this all sounds implausible, considering Fodor’s example will make his intent clear.
Consider someone learning a new word miv in a classical learning context. The subject is shown cards, some of which are miv and some non-miv. The subject is given a cookie whenever s/he correctly identifies the miv cards and is hit by a bolt of lightening when s/he fails (we want the reinforcement here to be very unambiguous). What does the subject do, according to any classical learning theory, s/he considers a hypothesis of the form “X is miv iff X is…”, the blank being filled in with a specification of the features that are criterial for being a miv. The data is then used to assess the truth of the hypotheses with various values of “…”. So if miv means “red and round” then the data will tend to confirm “X is miv iff X is red and round” and disconfirm everything else. This much Fodor takes to be obvious. If learning is a form of inductive inference (and, as he notes, there is no other theory of learning), then it takes the indicated form.
Fodor then asks where do the hypotheses that are tested come from? In other words, where do the fillers of “…” come from? They are GIVEN. Inductive theories presuppose that the set of alternatives that the data filter are provided up front. Given a hypothesis space, the data (environmental input) can be used to assign a number (a probability) of how well that hypothesis fits the data. What inductive theories don’t do is provide the hypothesis space. Another way of making the same point is that what inductive logics (i.e. learning theories) do is explain how given some input the user of that logic should/does navigate the hypothesis space: where’s the best place to be given that the data has been such and so. However, if this is what inductive logics do (and, I cannot repeat this enough, all learning theories are species of inductive logics), then the field of concepts used by the inductive logic cannot themselves be fixed by the inductive logic. Or as Fodor puts it (147):
You have to be nativistic about the conceptual resources of the organism because the inductive theory of learning simply doesn’t tell you anything about that – it presupposes it – and the inductive theory of learning is the only one we’ve got.
So, Fodor’s argument amounts to pointing out what everybody should be nodding in agreement with: no induction without a hypothesis space. If the inductive theory is a theory of learning, then the hypothesis space must be innate and that means that all the concepts used to define it must be innate as well. As I said, this part of the argument is apodictic, cannot be gainsaid and, in fact, never has been. Even Quine, a rather extreme associationist, agreed that everyone is a nativist to some degree for without some nativism (enough to define the hypothesis space) there can be no induction and hence no learning. Fodor’s point is to emphasize this point and use it against theories that suggest that one can bootstrap one’s way form less conceptually complex systems of “knowledge” to more complex ones. If this means that one can expand one’s hypothesis space by learning and ‘learning’ means induction then this is impossible.
None of this should be surprising or controversial. Controversy arises with respect to Fodor’s second prong of the argument. He takes the concepts words tag to be effectively atomic. Another way of making this point in the domain of language is that there is no lexical decomposition, or at least very very little. Why is this assumption so important? Because the relation between the input and the atomic features of the hypothesis space is causal, not inductive. You see a red thing and +red lights up. Pure transduction. Induction proceeds given this first step: count how many of the lit features are red+round vs red+not-round, vs green+round etc. So, for atomic features/concepts the relation between their “lighting up” and the environment is not one of learning (one doesn’t learn to light them up) it’s just a brute fact (they light up). So, and this is an important point, to the degree that most of our words denote atomic concepts (i.e. to the degree that there is no lexical decomposition) to that degree there is no interesting inductive theory of concept acquisition. Note, this does not preclude their being a possibly interesting causal theory, e.g. maybe being exposed to a miv is causally responsible for triggering the concept miv or maybe being exposed to a dax is causally responsible, or maybe being exposed to a miv right after birth is or while being snuggled by your mother etc. The causal triggers might conceivably be very complex and finding them may be very difficult. However, with resepct to atomic features, one can only discover brute causal connections, not inductive ones. Fodor’s point is that we should not confuse them as they are very different. Recently Fodor has speculated that prototypes are causally implicated in causally triggering concepts, but he insists, rightly given his strong atomicity, that this relation is not inductive (See here).
To recap, the logic of the first argument is that primitive concepts cannot be “learned” as they are presupposed for learning to take place. This allows the possibility that one “learns” to combine these primitives in various ways and that’s what concept acquisition is. Concept acquisition is just learning to form complex concepts. Fodor is conceptually happy with this possibility. It is logically possible that concept “acquisition” amounts to defining new concepts in terms of the primitive ones. As applied to words (which I am assuming denote concepts), it is logically possible that most/many words are complex definitions. Logically possible? Yes. Actually the case? No, or that’s what Fodor has been arguing for a very long time.
His arguments are almost always of the same form: someone proposes some complex definition for a term and he shows that it doesn’t work. Indeed, very few linguists, psychologists or philosopher have managed to provide any but a handful of purported definitions. ‘Bachelor’ may mean unmarried man, but as Putnam noted a long time ago, there are not many words like it.
Fodor is actually in a good position to understand this point for he along with Katz once investigated reducing meanings to feature trees. David Lewis derided this “markerese” approach to semantics (another instance of be careful what you hurl as it may boomerang back at you (see Paul on Harman on Lewis here)), but what really killed it was the realization that virtually all words bottomed out in terminal faetures referring to the very concept that the featural semantics was intended to explicate. So, e.g. the markerese representation for ‘cat’ ended up having a terminal CAT. This clearly did not move explanation forward, as Fodor realized.
So is Fodor right about definitions? Well, I am slightly less skeptical than he is about the virtues of decomposition, however, this said, I cannot find good examples showing him to be wrong. As the first part of his argument is unassailable, then those that don’t like the conclusion that ‘carburetor’ is innate (i.e. a primitive of our conceptual hypothesis space) had better start looking for ways of defining these words in terms of the available primitives. If past history is any guide, they will fail. Definitions in terms of sense data have come and (happily) gone and cluster concepts, once considered seriously, have long been abandoned. There is a little industry in linguistics working on argument structure in the Hale-Keyser (HK) framework, but, at least from where I sit, Fodor has drawn significant blood in his debates with HK aficionados. Suffice it for now to repeat, that this is where the action must be if Fodor is to be proven incorrect and the ball is clearly not in his court. It is easy to show that he is wrong, viz. show that most/many words denote complex concepts. How to show Fodor is wrong is easy. Showing that he is has proven to be far more challenging.
So that’s the argument. The first step is clearly correct. All the action concerns the second. One further point: there has been a lot of discussion in the thread that Fodor is advocating a nutty kind of nativism that eschews learning from the environment. As should be clear, this is simply false. If word learning is belief fixation then it can be as inductivist as you like. However, if word learning is concept acquisition then the question entirely revolves around the nature of the primitives concerning which everyone must take as innate and hence not acquired. Fodor’s bottom line is that hypothesis spaces are not acquired but presupposed and that as a matter of fact there is far less definition one might have supposed. That’s the argument; fire away!
 Alex Clark mentioned Sue Carey’s recent book that appeared to consider this bootstrapping possibility. Gallistel reviewed her book making effectively this point that induction/learning cannot expand a hypothesis space (here). To repeat, all that such theories show is how to most effectively navigate this space given certain data.
 One interesting avenue that Paul has been exploring revolves around Frege’s notion of definition. For Frege definition changed a person’s cognitive powers. This is really interesting. Paul’s work starts from Jeff Horty’s discussion of Frege’s notion (here and considers how to extend it to theories of meaning more generally (c.f. here and here).