Reductive Materialism (Physicalism) Identity Theory Mental events are strictly identical with brain events. Type identity vs. token identity: Type-type identity theory: Mental event types are identical to brain event types. E.g., Pains are C-fiber-firings Token-token identity theory: Token mental events are identical to token brain events. E.g., My pain in my right hand at time t is identical to the particular C-fiber-firing in my CNS at time t. UT Place & DM Armstrong on is statements 1
Metaphysical or semantic? The Identity Theory can be expressed semantically: Take the following identity sentence as an example: P: Pain = C-fiber-firing The IT claims that the terms pain and C-fiber-firing refer to one and the same thing. The theory does not claim that the terms have the same meaning. Keeping this distinction between identity of meaning and identity of reference in mind is crucial for the theory to avoid certain objections to it. (Why does Smart talk about translation of psychological sentences?) IT makes a synthetic a posteriori claim, i.e. the sort of claim that can be known only on the basis of observation and that can be true or false depending on how the world turns out to be (not on the basis of meaning) synthetic vs analytic (semantic) a posteriori vs. a priori (epistemological) contingent vs. necessary (metaphysical) The IT theorist claims that the sort of mind-brain identities, like pain=c-fiber firing, envisioned is of the same kind of scientific identities discovered. 2
IT modeled on scientific identities Examples: The temperature of a gas is the mean kinetic energy of its molecules Water is H 2 O Cows are animals with the genetic code GACCTAGCTA... Lightning is electrical discharge of ionized water molecules Gold is the element with atomic number 79 Etc Objection #3 (Max Black s Objection to IT) For suppose we identify the Morning Star with the Evening Star. Then there must be some properties which logically imply that of being the Morning Star, and quite distinct properties that entail that of being the Evening Star. Again, there must be some properties (for example, that of being a yellow flash) which are logically distinct from those in the physicalist theory. 3
JJC Smart Reference and Meaning -- Venus The Morning Star The Evening Star (D1)The last star to disappear (D2) The first star to appear in the in the morning skies evening skies Property1 Property 2 Venus Reference and Meaning -- Pain Pain C-fiber firings (D1)?? (D2) Such and such neural firings irredicibly psychic Phenomenal feel property??? Property 2 Property Dualism? C-fibers firing 4
Smart s response: Topic-neutral analyses "I see a yellowish-orange after-image, roughly means (is this really plausible?); There is something going on which is like what is going on when I have my eyes open, am awake, and there is an orange illuminated in good light in front of me, that is, when I really see an orange." Descriptions in terms of objective stimulus conditions for normal observers. We report our own sensations in topic-neutral language and we conceive of them as such too. S Kripke Rigid reference Pain & C-fiber-firings Pain (rigid designators) C-fiber firings directly refers directly refers? Pain C-fibers firing 5
Descartes Conceivability Argument in Meditation #6 And first of all, because I know that all things which I apprehend clearly and distinctly can be created by God as I apprehend them, it suffices that I am able to apprehend one thing apart from another clearly and distinctly in order to be certain that the one is different from the other, since they may be made to exist in separation at least by the omnipotence of God; and it does not signify by what power this separation is made in order to compel me to judge them to be different: and, therefore, just because I know certainly that I exist, and that meanwhile I do not remark that any other thing necessarily pertains to my nature or essence, excepting that I am a thinking thing, I rightly conclude that my essence consists solely in the fact that I am a thinking thing [or a substance whose whole essence or nature is to think]. And although possibly (or rather certainly, as I shall say in a moment) I possess a body with which I am very intimately conjoined, yet because, on the one side, I have a clear and distinct idea of myself inasmuch as I am only a thinking and unextended thing, and as, on the other, I possess a distinct idea of body, inasmuch as it is only an extended and unthinking thing, it is certain that this I [that is to say, my soul by which I am what I am], is entirely and absolutely distinct from my body, and can exist without it. 11 6