For some time I had been writing about the pervasive influence of functionalism across a wide range of disciplines. I was then invited by the Course Team to contribute a Unit to a new course on 'Science and Belief: from Darwin to Einstein', so I adapted my argument to that pedagogical context and mode of expression. The results is a rather odd mixture of critique and exposition, but I cannot recast it at this distance in time. It is, I think, my clearest expression of the critique of scientism, in particular, biologism, in the human sciences. The essay first appeared as an Open University Course Unit for 'Science and Belief: from Darwin to Einstein', Block VI: Problems in the Biological and Human Sciences. Milton Keynes: Open University Press, 1981, pp. 63-110.