Professor C. A. Mace, the psychologist, once wrote: ‘It is difficult … to present and defend any sort of behaviourism whatever without committing oneself to nonsense.’ I shall illustrate this thesis. I shall comment on the writings of some psychologists. This is relevant to my topic; for psychologists' expositions of behaviourism contain much more philosophy than science, and the inconsistencies which permeate their versions of behaviourism reappear in the works of eminent philosophers. My quotation from Mace comes from a paper defending what he calls ‘analytical behaviourism’; which he distinguishes from ‘methodological behaviourism’ and ‘metaphysical behaviourism’. According to Mace, analytical behaviourism does not question the truth of our everyday statements about a person's mind or states of consciousness; what it claims is that such statements ‘turn out to be, on analysis, statements about the behaviour of material things’, that is, about a person's ‘bodily acts, bodily states, bodily dispositions, bodily “states of readiness” to act in various ways’. The father of behaviourism, J. B. Watson, rarely says anything suggesting this doctrine. As he presents it, behaviourism is both a methodological principle and a metaphysical theory.