What Synaesthesia Really Tells Us About Functionalism

J.A. Gray et al. (2002) have recently argued that synaesthesia can be used as a counterexample to functionalism. They provide empirical evidence which they hold supports two anti-functionalist claims: disparate functions share the same types of qualia and the effects of synaesthetic qualia are, contrary to what one would expect from evolutionary considerations, adverse to those functions with which those types of qualia are normally linked. I argue that the empirical evidence they cite does not rule out functionalism, rather the reverse. The fact that the effects of synaesthesia are adverse shows that understanding synaesthetic experiences requires a concept of dysfunction, which in turn presupposes a functionalist account. Such an account, moreover, shows how tokens of the same types of qualia can be associated with different causal histories, thus disarming their first objection.