(i) Conscious states are describable independently of our awareness of brain processes.
(ii) The verification conditions for statements about consciousness and brain processes are entirely independent.
(iii) There is nothing self-contradictory in the thought that some subject has a conscious experience without any correlated brain process.
There maybe problems among these, but, as Place notes, even granting (i), (ii), and (iii), it doesn’t follow that the claim ‘consciousness is a brain process’ is necessarily false. Rather, ‘consciousness is a brain process’ is neither self-contradictory nor self-evident.
Consider the following sentences, which have the feature that the subject expression and the object expression appear to be adequate characterizations of the same things/states of affairs:
(D1) A square is an equilateral rectangle.
(D2) Red is a color.
(D3) To understand an instruction is to be able to act appropriately under the appropriate circumstances.
(C1) His table is an old packing case.
(C2) Her hat is a bundle of straw.
(C3) A cloud is a mass of particles in suspension.
Contrast these with the following examples:
(P1) Toby is eighty years old.
(P2) Her hat is red.
(P3) Giraffes are tall.
Place claims that one reason for holding that D-sentences and C-sentences have the feature that the subject term and object term are adequate characterizations of the same thing is that in both cases we can reasonably add the clause ‘and nothing else’ to them. Compare:
(D1*) A square is an equilateral triangle and nothing else.
(C3*) A cloud is a mass of particles in suspension and nothing else.
Compare with a P-sentence:
(P3*) Giraffes are tall and nothing else.
P-sentences don't seem to have the property in question. This is plausibly just because the relation does not seem to be between independently adequate descriptions of the same things.
Aside from the similarity pointed out, D-sentences differ from C-sentences in that the former appear to be necessarily true by definition and the later only contingently true (on condition of verification). For D-sentences, there is a logical/conceptual/analytic relationship such that the subject term picks out something contained in the predicate term. Presumably, this is what Place means by the ‘‘is’ of definition.’
By contrast, for the ‘‘is’ of composition’, there is no such (apparently) analytic relationship between the terms. The two terms involved seem to adequately describe each other (for a given context), but it is only contingently true that they do so. This goes even for (C3), which stands out because it lacks an indexical component.
Why assume that we can deny the claim that 'consciousness is a brain process' on strictly logical grounds in the first place? The argument that Place is criticizing, initially, is this:
(1) If the meanings of two expressions differ, they can’t both provide an adequate characterization of the same object.
(2) There is no contradiction in conceiving of a conscious state which is not underwritten by a brain process.
(3) The meanings of ‘consciousness’ and ‘brain process’ differ (are conceptually independent).
(4) Therefore, ‘consciousness’ and ‘brain process’ cannot be adequate characterizations of the same thing.
(5) Therefore, consciousness is not a brain process.
Place digs in right at the beginning; at premise (1), offering a kind of error theory that might help to motivate the identity theory. It is a mistake to assume that where meanings of expressions differ, that both cannot adequately describe the same thing, in effect, there are true, contingent identity statements. After all, if we were to subscribe to the faulty assumption (says Place), then we might wind up in the weird position of having to assert that it is logically impossible for any table to be an old packing case; since, there is no contradiction in asserting that someone has a table but not a packing case. The same would presumably go for the impossibility of any hat being a bundle of straw, or any cloud being a conglomeration of particles. [t-b-cont’d]
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