A Logical Positivist’s Progress: A Puzzle about Other Minds in Early Ayer Resolved

This chapter considers how knowledge of other minds is dealt with in Ayer’s Language Truth and Logic (LTL) of 1936 and then reported in his later works to the end of his career. It endeavors to show, first, that the theory outlined in LTL differed from the theory which Ayer himself criticized LTL for proposing when only a few years later in The Foundation of Empirical Knowledge of 1940 he offered an alternative theory of our knowledge of other minds (which also was rejected later on) and ever since. Second, this paper documents that this change in how Ayer presented the LTL argument coincided with a sharp change in how he understood his own philosophical position: from a highly idiosyncratic version of logical positivism Ayer reverted back to a largely traditional phenomenalism of the British empiricist variety. If another indication were needed of how inappropriate it is to think of Ayer’s ideas as representative of Vienna Circle philosophies, this paper provides one. The interest and significance of Ayer’s philosophy rather lies in the distinctive failures that are peculiarly its own and which, as regards knowledge of other minds, display in an instructive fashion the tension between competing intuitions that condemn still-residually Cartesian epistemologies like his to futility.