brain states. (As Putnam points out, and as Smart did,
if this argument was good it would count against almost any scientific theoretical
identification.)
Putnam begins ‘The nature of mental states’ by agreeing with a lot of claims that we
saw Smart making. Putnam agrees with Smart that it is coherent to think of the
identification of pains and other mental states with brain states as the same kind of claim
as other theoretical identifications in science, and agrees further that the fact that
one can know that one is in pain without knowing much about one’s brain state
does not show that pains brain states. (As Putnam points out, and as Smart did,
if this argument was good it would count against almost any scientific theoretical
identification.)
His argument against the view is not that it is nonsense, but that when we look at what it would take for the identity theory to be true, we can see that it is very unlikely to be true:
“Consider what the brain state theorist has to do to make good his claims. He has to specify a physical-checmical state such that any organism (not just a mammal) is in pain if and only if (a) it possesses a brain of a suitable physical-chemical structure; and (b) its brain is in that physical-chemical state. This means that the physical-chemical state in question must be a possible state of a mammalian brain, a reptilian brain, a mollusc’s brain ...etc. At the same time it must not be a possible ...state of the brain of any physically possible creature that cannot feel pain. Even if such a state can be found, it must be nomologically certain that it will also be a state of the brain of any extraterrestrial life that may be found that will be capable of feeling pain before we can even entertain the supposition that it may be pain.
...
Finally, the hypothesis becomes still more ambitious when we realize that the brain-state theorist is not just saying that pain is a brain state; he is, of course, concerned to maintain that every psychological state is a brain state. Thus if we can find even one psychological predicate which can clearly be applied to both a mammal and an octopus ...but whose physical-chemical ‘correlate’ is different in the two cases, the brain-state theory has collapsed.” (436-7)
Arguments of this form against identity theories of mental states are sometimes called arguments from ‘multiple realizability.’ How is the argument supposed to work? Is it plausible?
Putnam’s paper is not just aimed at arguing against physicalism; he also introduces a new theory of mental states, which he expresses as the view that a mental state like pain is “a functional state of a whole organism.” (433)
What does he mean by this? What is a ‘probabilistic automaton’? How can this theory be compatible with both materialism and dualism, as Putnam says it is (436)?