1. Related in conversation by Professor Sellars.

2. Brentano's distinction between "mental" and "physical" phenomena seems to have been meant as a distinction between intentional states and qualia, not ( pace Professor Chisholm) as a distinction between what English-speaking philosophers would normally call mental and physical objects . (For a convincing argument to this conclusion, see McAlister [1974].) The directedness of cognitive states sets them apart from both sorts of "physical" things, but the specific nature of Brentano's distinction is a consequence of his "empiricism" being of the philosophical rather than the experimental sort.

3. Chisholm's criteria for the "intentionality" of sentences are formulated in terms of features of the subordinate clauses of the verbs used to denote propositional attitudes, which do not admit of existential generalization or substitutivity of identicals. Uses of referring terms that do not admit of existential generalization or substitutivity of identicals are also called "opaque." Thus a considerable number of writers use the expression "intentional" to denote a class of sentences marked by opacity of reference. (Some writers, notably Fodor and Searle, employ a separate spelling for this Chisholmian usage of the word: namely, 'intensionality' with an s. This usage is not to be confused with the "intension" of the Port Royal logicians, which is defined in contrast with extension.)

4. See, for example, Rudolph Carnap (1938:144-146 ff.) for the reduction of biology and psychology to physics.

5. It is worth mentioning that in a preface to the reprinting of this article in Block (1980: 14), Hempel indicates that he has long since rejected logical behaviorism and that the article is "far from representing [his] present views." Logical behaviorists, however, were often at pains to distance themselves from claims about ( a ) the ontology of mind and ( b ) the proper methodology for psychology. Hempel, for example, clarifies the relation of logical behaviorism to existence claims involving the mental by saying that "logical behaviorism claims neither that minds, feelings, inferiority complexes, voluntary actions, etc., do not exist, nor that their existence is in the least doubtful. It insists that the very question as to whether these psychological constructs really exist is already a pseudo-problem, since these notions in their 'legitimate use' appear only as abbreviations in physicalistic statements" (Hempel [1949] 1980: 20). As for psychological methodology, Hempel writes that his thesis, though "related in certain ways to the fundamental idea of behaviorism, does not demand, as does the latter, that psychological research restrict itself methodologically to the study of the responses organisms make to certain stimuli" (Hempel [1949] 1980: 20).

6. Compare the discussion of this development in Herbert Feigl (1958: 371-372). break

7. Putnam and Oppenheim (1958: 7) write, for example,

It is not absurd to suppose that psychological laws may eventually be explained in terms of the behavior of individual neurons in the brain; that the behavior of individual cells—including neurons—may eventually be explained in terms of their biochemical constitution; and that the behavior of molecules—including the macro-molecules that make up living cells—may eventually be explained in terms of atomic physics. If this is achieved, then psychological laws will have, in principle, been reduced to laws of atomic physics.

8. The precise form of logical behaviorism is best understood as a result of the epistemological concerns of early Vienna Circle positivism. Skinner's operationalism is a result of his concern about methodological rigor. The reductive physicalist's views are best understood, by contrast, in terms of an atomistic view embracing ( a ) an ontological commitment to materialistic monism, ( b ) a commitment to the "completeness" or "generality of physics"—i.e., the view that every token event may be explained wholly in physical terms—and ( c ) a metatheoretical assumption that the properties relevant to high-level sciences like psychology can, in principle, be identified with (coextensive) complex physical properties, even if the predicates of physics are not synonymous with those of the special sciences.

9. One also finds phenomenalism and neutral monisms in the early positivist writings.

10. The scare quotes are Turing's (1936: 231).

11. Hilary Putnam, "Minds and Machines" (1960), is the classic source in the philosophy of mind for the Turing machine analogy. Fodor's "Explanations in Psychology" (1965) and "The Appeal to Tacit Knowledge in Psychological Explanation" (1968) espoused a similar functionalist view, but did not make specific use of the Turing machine analogy.

12. Fodor (1981: 24) alludes to both problems when he writes, "Functionalism tends to vindicate Realistic construals of mentalistic etiologies; but it does not, per se, vindicate a Realistic reading of etiologies in which appeals to propositional attitudes figure."