One goal of recent philosophy of mind has been to ‘naturalize’ intentionality by showing how a purely physical system could have states that represent or are about items (objects, properties, facts) in the world. The project is reductionist in spirit, the aim being to explain intentional relations—to say what they really are—and to do so in terms that do not themselves utilize intentional or semantic concepts. In this vein there are attempts to explain intentional relations in terms of causal relations, informational relations, teleological or functional relations, relations involving abstract similarity or isomorphism, and various combinations thereof.2 What makes these accounts naturalistic is the presumed objectivity and scientific respectability of the properties appealed to in the explanans. What makes them all reductive is their shared presumption that intentionality can be explained in terms that have a wider application to intentional systems as well as to systems that have no mental properties at all.

I emphasize the reductionism implicit in the naturalizing project because it the source of an ongoing debate amongst naturalist sympathizers. Some, like Fodor, see a successful reduction of intentional relations as necessary for a naturalistic world-view. As he puts it: