In Doing without Concepts, Machery (Reference Machery2009) argues that concepts should be eliminated from psychology. He further claims that psychological and philosophical theories of concepts talk past each other: “when philosophers and psychologists develop theories of concepts, they are really theorizing about different things” (p. 4). I am not convinced that concepts should be eliminated from psychological theorizing, but today, I focus on Machery's claim that concepts play entirely different roles in philosophy and psychology: I shall aim for a partial reconciliation in the context of one well-known philosophical theory of concepts, Conceptual Atomism (CA), a view pioneered by Jerry Fodor (see Fodor Reference Fodor1998; Laurence & Margolis Reference Laurence and Margolis2002).

According to Machery (Reference Machery2009), philosophical theories are mainly interested in concepts as they figure as constituents in propositional attitudes and hence find the matter of reference determination to be of key import. Psychological theories, in contrast, focus on topics such as categorization, analogical reasoning, and induction (p. 34). As an example of how divorced philosophical and psychological interests are, Machery raises CA:

CA claims that the nature of a concept is determined (or, as philosophers say, “individuated”), at least in part, by the information that the symbol carries about the world. It further holds that lexical concepts are primitive, being semantically unstructured: that is, they are not comprised of further concepts (Fodor Reference Fodor1998; Margolis & Laurence Reference Margolis and Laurence1999, p. 62; Prinz Reference Prinz2002, p. 89).

Many would agree with Machery's claim that CA ignores the role that concepts play in thought (i.e., categorization, induction, etc.). Still, Machery's conclusion is premature. Surprisingly, CA has a neglected resource for capturing the role the concept plays in thought; this is because, as we'll see, according to CA, a concept is defined by its symbol type. For, consider that CA defines primitive concepts in the following manner:

(Where the broad content of a symbol is, roughly, what the symbol refers to.)

The reader may be surprised that I construe CA as saying that symbols individuate concepts. But observe that Fodor himself acknowledges that broad content alone is inadequate for the purpose of individuating primitive concepts because it fails to distinguish co-referring concepts (e.g., groundhog/woodchuck; Cicero/Tully) (Fodor Reference Fodor1998; Reference Fodor2008). He explains that it is for this reason that he distinguishes concepts in terms of their mode of presentation (MOP) types, as well as their broad contents (Fodor Reference Fodor1998, Chs. 1 and 2; Reference Fodor2008, Ch. 3, especially p. 70). And, as philosophers know, Fodor regards MOPs as being symbols. Hence, even working within Fodor's original framework, CA has the resources to individuate concepts along two dimensions: a symbolic dimension and a referential one.

Now let us see how CA's symbolic element captures the role the concept plays in thought. I have argued that symbols are defined by the role they play in computation (Schneider Reference Schneider2009). Although Fodor, ironically, challenges aspects of my view, notice that even Fodor himself writes that MOPs (i.e., symbols) are individuated by their role in mental processing: “If MOPs are both in the head and functionally individuated, then a MOP's identity can be constituted by what happens when you entertain it” (Fodor Reference Fodor1998, p. 20; see also Fodor Reference Fodor2008, p. 92).

Piecing these observations together, we are now ready for the payoff. When CA is properly understood, both psychological and philosophical interests are brought together into a singular package: A lexical concept is a semantically unstructured “atom” that is individuated by both its meaning (in particular, its broad content) and its symbol type, where the symbol, in turn, is individuated by the computational role that it plays in one's cognitive economy (including, importantly, its role in mental processes such as categorization, induction, and analogical reasoning) (Schneider Reference Schneider2009; forthcoming). So CA can say that the features of concepts that psychologists are traditionally interested in are built into concepts' very natures. For example, consider the prototype view. In the eyes of CA the experimental results in the literature on prototypes are indications of features of certain symbols' underlying computational roles, and these roles determine the relevant concept's natures.

CA is ecumenical. For now consider the competing theory-theory, which suggests that concepts are mini-theories of the categories that they represent, encompassing our beliefs about hidden features, underlying causal mechanisms, and ontological divisions. Advocates of the theory-theory suggest that it captures explanatory relations between features while the prototype theory does not. For instance, in a well-known criticism of the prototype view, children appear to use beliefs about a creature or thing's underlying essence to override categorization judgments based on superficial, sensory features (Keil Reference Keil1989). In the eyes of the conceptual atomist, this debate provides insights regarding concepts' underlying computational roles. But no matter how the debate plays out, concepts' natures are nevertheless determined by their broad contents and symbol types. Indeed, perhaps some concepts have computational roles that are explained by the prototype view, while others have roles that are illuminated by the theories view.

So the conceptual atomist who pays attention to the neglected, symbolic element of concepts can offer a more comprehensive theory of concepts than is normally supposed. CA is ecumenical enough to incorporate different sorts of concepts (prototypes, theories, etc.), and it also speaks to philosophers' traditional interest in reference determination. Finally, although I have focused on the LOT approach, my remarks can apply to philosophical approaches to concepts more generally, insofar as they individuate concepts by both meaning and computational (or functional) role.