Hempel, Carl Gustav (1905–1997)

Hempel’s defence of Carnap’s and Neurath’s physicalism testifies to the presence of certain ‘postmodern’ themes in logical empiricism (or logical positivism): (1) a textualist turn to sentences from the facts or reality they are said to report; (2) a pragmatic turn from truth to inclusion in the text as the basic scientific concern; and (3) a descriptive turn from logic to empirical sociology of science. Throughout his philosophical writings Hempel held that the question of what truth-claims mean should be replaced by the question of what criteria we use in deciding whether or not to call sentences true. Granted that ‘Whales are mammals’ is true if and only if whales are mammals, the question remains of how observation reports bear on whether or not to include a sentence in the text of current knowledge, and how received observation sentences may be dropped from it. For Hempel, then, the problem of analysing the concept of confirmation of sentences by sentences is either the heart of the problem of truth or the successor to that problem. Like Carnap, in 1945 he thought such an analysis necessary to connect the terms ‘logical’ and ‘empiricism’; but four decades later he would conclude that, after all, one must ‘leave the decision in matters of confirmation to the intuitive appraisal of the scientist’ (1945b: 98).