Fodor’s anti-Darwinism

The structure of Fodor’s argument against Darwinism (a paraphrase of the summary in his paper):

1. Explaining the distribution of a phenotypic trait in a population requires determining which trait[s] were selected for, not just which traits happened to be selected. In particular, it requires determining which of two coextensive traits was the one that was selected for.
2. To determine which of two coextensive traits was the one selected for, we have to consider counterfactuals about which of them would be selected for in possible worlds where they are not coextensive.
3. Such counterfactuals can be answered only if there (a) there is an agent that does the selecting, or (b) there are laws of selection.
4. There is no agent that does the selecting in Darwinism.
5. Due to contextual sensitivity, there are probably no laws of selection.

Conclusion: Darwinism cannot explain the distribution of phenotypic traits in a population.

As I see it, 4. is the only premise that is relatively unproblematic. 1., I think, indicates how Fodor misunderstands Darwinism/natural selection. It is simply untrue that “explaining the distribution of a phenotypic trait in a population would require a notion of ’selection for’ a trait.” This had already been pointed out to Fodor by Coyne and Kitcher, but evidently he didn’t accept their point. It is quite possible to explain the distribution of traits in a population by how certain genes/individuals/groups (pick your favourite level of selection) were simply [plain vanilla] selected. I doubt that biologists who use the phrase ’selection for X’ really mean ’selection for’ in the way Fodor construes it — when pressed, they would concede that it really is just ’selection of’. ‘Selection for’ is more like a useful mode of thinking that is often wrong but produces enough fruitful predictions that it continues to be used.

Perhaps Fodor wasn’t thinking of the sophisticated explanations of the Modern Synthesis of evolutionary biology — perhaps his ‘Darwinism’ is vastly different from that. In his Darwinism, it would seem that distributions of traits can be explained only by their being selected for. It is, in short, indistinguishable from an extreme version of adaptationism. Which would explain very nicely how he claims to have discovered the fatal flaw of Darwinism from a consideration of adaptationist evolutionary psychology (EP). It would also explain why he thinks evo-devo is evidence against ‘Darwinism’. His argument as laid out above may be OK against EP, but not against any non-adaptationist version of ‘Darwinism’. And I doubt (although, as I’m neither a biologist nor philosopher of biology, I may be wrong on this) it’s conventional usage to equate Darwinism with strictly adaptationist natural selection. Indeed, the SEP article on Darwinism (written by James Lennox) does not list adaptationism or anything resembling it as one of its principles. All we get there, in fact, is exactly the kind of ’story’ that Fodor derided Coyne and Kitcher for providing:

The theory can be set out as a series of causal elements that, working together, will produce the needed transformations.

1. Species are comprised of individuals that vary ever so slightly from each other with respect to their many traits.
2. Species have a tendency to increase in size over generations at an exponential rate.
3. This tendency, given limited resources, disease, predation, and so on, creates a constant condition of struggle for survival among the members of a species.
4. Some individuals will have variations that give them a slight advantage in this struggle, variations that allow more efficient or better access to resources, greater resistance to disease, greater success at avoiding predation, and so on.
5. These individuals will tend to survive better and leave more offspring.
6. Offspring tend to inherit the variations of their parents.
7. Therefore favorable variations will tend to be passed on more frequently than others, a tendency Darwin labeled ‘Natural Selection’.
8. Over time, especially in a slowly changing environment, this process will cause the character of species to change.
9. Given a long enough period of time, the descendant populations of an ancestor species will differ enough to be classified as different species, a process capable of indefinite iteration. There are, in addition, forces that encourage divergence among descendant populations, and the elimination of intermediate varieties.

Note that there is nothing in this account that says that the every distribution of every phenotypic trait can be explained by natural selection, or even that most such distributions can. And because this account does not require traits to be selected for, we don’t have to care about answering counterfactuals about possible worlds where polar bears are white but do not match their environment. Hence we don’t need to have laws of selection. In fact, Peter Godfrey-Smith’s reply to Fodor was that there aren’t laws of selection, but not every scientific theory needs to have laws, so it’s not a problem that natural selection doesn’t. Fodor’s reply to him reveals what I think is an appalling lack of understanding of the empirical status of natural selection:

I’m puzzled as to what Godfrey-Smith takes the substance of the theory of natural selection to be. ‘ [W]e can think of the textbook as describing abstract processes, describing actual-world mechanisms, and also bringing the two together… ’ (p. 35). So, is adaptationism merely the thesis that speciation is the product of [some or other] mechanisms and abstract processes? Cf. ‘ we had to destroy it in order to defend it ’ . With such friends, Darwin doesn’ t need enemies.

I have no idea why he feels that “merely” is appropriately used there — why he thinks Godfrey-Smith’s description of the theory of natural selection is demeaning. Any set of “mechanisms and abstract processes” that gives us the quantity and quality of predictions about empirical observations that we have from natural selection should not be brushed aside with a blithe “merely”.

And what of Fodor’s claim, near the end, that although explanations via natural selection aren’t nomic, they can be ’salvaged’ as ‘historical narratives’? Although I agree that they probably aren’t nomic, I would have to disagree that they are necessarily post hoc. The theory of natural selection is not solely concerned with explaining the past. It also does an admirable job of predicting future observations, as admirably (dare I say) as the likes of quantum mechanics. It’s not just that when such explanations work “they provide plausible historical narratives”. It’s a lot more than that.

Turns out Fodor has a response to the ‘but it works’ line as well (nestled in his reply to Dennett):

‘But it works’. That’s not obvious; in fact, it’s what is in dispute. To be sure, the theorist can often distinguish between confounded variables; but it doesn’t follow that the theory can since the theorist has much more than the theory to go on: In particular, he has access to all sorts of intuitions about the relative plausibility of one or other natural-history scenarios. (That’s why selectionist explanations, like historical explanations, aren’t always just-so stories.) It’s often a delicate matter to distinguish what the theorist knows from what the theory tells him; but it ’ s essential to do so if one is to determine what the data do or don’t say about the confirmation of theory.

Too bad he doesn’t say anything about how the theory works beyond providing plausible historical narratives. People aren’t just working on ‘intuitions’ about the mere plausibility of natural scenarios. They have hard, quantitative evidence, gleaned from paleontology and genetics.

I’ll cap off with an amusing observation: In their replies, both Sober and Dennett take Fodor’s argument as a reductio that should lead Fodor to abandon one or more of his premises. Fodor, however, embraces what Dennett calls the ‘absurd conclusion’. Dennett expends nearly a full page mocking him for that, which only invites an even more childish reply from Fodor:

Dennett fears that scientists won’t take me or my sort of arguments seriously. I might not get invited to the Biology Department ’ s Spring Picnic, which would put a terrible hole in my social schedule. But I am dauntless; if it be so, then so be it. I have spent about fifty years palling around with scientists, and here is what I have discovered: They are a lot like us. That is, they are often precipitous and confused and not reliable as to the significance of their theories and discoveries. It is therefore desirable to distinguish between two quite different methodological principles, one of which I cleave to but the other of which I treat with circumspection. Namely: ‘take the science seriously’ and ‘take the scientist seriously’ . Often enough, in my experience, doing the one precludes doing the other.

Well, I hardly think that scientists have the last say on everything, but in this matter it really is a case of Fodor not taking the science seriously either — if he did he would not condemn all the correct predictions the theory of natural selection has made about genetics experiments (say) as ad hoc “historical narratives”.