In proposing to dispense with concepts in Doing without Concepts, Machery (Reference Machery2009) neglects to notice how psychological explanation presupposes them. How could we begin even to describe, for example, the Müller-Lyer illusion unless people share a concept of longer than; or the gambler's fallacy, without them sharing more likely? Concepts seem to be natural kinds at least to the extent that they are the entities over which psychology generalizes.

But what is a concept that can play this role? Many recent philosophers (other than the atypical Peacocke [Reference Peacocke1992]) have offered proposals that Machery amazingly ignores, such as the various forms of “externalist” views that have been proposed by, for example, Kripke (Reference Kripke1972/1980), Putnam (Reference Putnam1975), Dretske (Reference Dretske1981), Devitt (Reference Devitt1981; Reference Devitt1996), Millikan (Reference Millikan1984), Burge (Reference Burge1986), and Fodor (Reference Fodor1990; Reference Fodor1998), according to which the identity conditions for a concept are provided in part by historical and counterfactual relations the thinker bears to phenomena in the external world. At most, Machery considers some of the “intuitions” that motivate externalism, only to dismiss them as too cross-culturally variable and unreliable.Footnote ²

Machery correctly notes that a problem with many traditional philosophical accounts like Peacocke's is that they fall afoul of Quine's attack on the analytic/synthetic distinction (Machery Reference Machery2009, p. 39). But he misses how that attack threatens any purely epistemic proposal, including his own appeal to “bodies of knowledge” (p. 12). This is puzzling, given Fodor's extensive discussion of many of these issues in at least five of his recent books, a discussion quite often directed explicitly at the psychological theories Machery considers. The problem is that “bodies of knowledge” vary between people and stages in a person's life. Unless one restricts the relevant knowledge in some principled way, no two people (or stages) will share a concept, since, short of coincidence, no two people (or stages) will bring exactly the same knowledge or procedures to bear in making many of their judgments.Footnote ³ Call this the problem of epistemic variability. Rather than inviting us to abandon the notion of concept, perhaps this variability is simply a reason to abandon an epistemic conception of it.

Machery would probably reply that I'm merely pressing here the philosophical notion of concept, which is concerned with the individuation of propositional attitudes (Reference Machery2009, pp. 32–33), a topic that, surprisingly, he claims is not the concern of psychological theory (p. 34). Indeed, he claims that when the two tasks are properly distinguished, “most philosophical attacks against the psychological theories of concepts are decisively undermined” (p. 51).

“Decisively”? There are a number of important reasons to think not: In the first place, as Machery himself notes (Reference Machery2009, pp. 35–37), many psychologists themselves are hardly clear about the difference between the two concerns, often presenting their work as refuting the Classical View of traditional philosophy and presupposing some philosophical, usually verificationist alternative (see Rey Reference Rey1983).

Secondly, concept identification would seem to be an issue not about how people do think under pressure, but how they could think if they were to reflect – what they could understand – and, pace Machery (p. 34), this seems as apt a topic as any for psychological research. It may well be that peoples' prototype of a doctor is of a man in a white coat; but if they found the thought of young woman doctor in a dark one as unintelligible as a round square, that would be a reason to think they didn't have the concept doctor. It's because people have a concept doctor that transcends their prototypes that it's worth reasoning with them, that is, modifying their epistemic position by citing evidence or argument, but keeping the concept the same. As I emphasized in Rey (Reference Rey1985), we need to distinguish the concept of something from merely the (epistemic) conceptions of it that have been too much the focus of the psychological research Machery reviews. Concepts are what remain stable across variability in conceptions, and so give argument a point, framing the questions of what people could learn and what might be the limits of reason and thought.

Lastly, as Machery notes, there is a need of a “coherent framework” (Reference Machery2009, p. 247) for bringing together the psychologists' different proposals. Something like the externalist strategies may be just the sort of thing for the purpose. They at least address the problem of epistemic variability in a promising way, proposing that concepts are constituted by what is “explanatorily basic.”Footnote ⁴ A crucial feature of this strategy is that it makes no commitment to the character of the representations people use in ordinary circumstances requiring rapid reasoning, or even in “acquiring” the concept (thereby also allowing for many concepts to be innate).

Nothing I have said here is meant to suggest that any externalist (or other) proposals are yet satisfactory (see Segal [Reference Segal2000] and Rey [Reference Rey, Kompa, Nimtz and Suhm2009a] for serious qualms). It's not that Machery should have endorsed externalist or related strategies; my point is simply that he should have discussed them, particularly before giving up on the concept of concept entirely.