Mind, identity theory of

3. Qualia

There was, however, one early objection to the identity theory that proved harder to dismiss. It concerns a perennial problem in the philosophy of mind: the nature of conscious experience and the sensuous side of psychology. But first, some stage setting.

The identity theory of mind is typically seen as part of the programme of giving a purely naturalistic or physicalistic view of the mind (see Materialism in the philosophy of mind). It is not a species of dual attribute theory of mind, according to which, although mental states are brain states they are brain states with special, non-physical properties, properties quite distinct from the kinds of properties neuro-science in particular, and the physical sciences in general, might attribute to them. The problem with dual attribute theories is that the question of how, in the light of what science is teaching us about the physical nature of the causation of behaviour, these non-physical properties could be causally relevant to behaviour seems just as pressing as the question, raised earlier, of how non-physical states could be causally relevant to behaviour. In consequence, most identity theorists see their theory as a purely naturalistic account of the mind: the denial of ‘spooky’ properties or attributes is as much part of the theory as the denial of ‘spooky’ entities or states.

The perennial objection is that the identity theory, when seen, as it should be, as part of a purely naturalistic view of the mind, leaves out the nature of conscious mental experience, the phenomenal side of psychology. We distinguish those mental states that are not associated with a characteristic ‘feel’ from those that are. Paradigmatic examples are belief, on the non-sensuous side, and bodily sensations and sensory perceptions, on the sensuous side. My belief that the world is round does not have a characteristic conscious feel available to introspective awareness; my itch and my sensing of a red sunset do. But, runs the objection, no amount of neurophysiological information about our brains tells us what it is like to itch, see a sunset, or smell a rose. Protagonists of this objection often use the term ‘qualia’ (‘quale’ is the singular) for the special properties that they insist that the identity theory leaves out of account. Typically, they hold that these qualia are epiphenomenal features. They avoid the implausibility of denying that pains and sensings of red per se are causally inefficacious but acknowledge that they have to allow that the distinctive feel of pains and sensings of red is causally irrelevant (see Qualia).