Originally published in 1988, this important study is a philosophical critique of the basic tenets of behaviourism in academic psychology as developed by B. F. Skinner and J. R. Searle’s conception of mind and its relation to the brain. Prof. Dilman sees their work in its proper context, as symptomatic of a much wider trend in human thought but criticises them on their individual merits. He connects Skinner’s behaviourism with that of the early Greek sophis, Gorgias, who sought to change people’s minds whilst bypassing their understanding. Dilman also claims that Searle’s scientific materialism is in reality a metaphysical position which cannot be supported by reference to the physical sciences. But the book is a discussion of their particular views and argues that they are open to serious philosophical objections. Today it can be read in its historical context.