Popper's philosophy is founded on his early conceptions of the problem of demarcation, of its solution, and of the roles of epistemology and methodology. I shall give an account of these, and of his idea of the alternative, ‘naturalistic’ conceptions. I then hope to show that Popper's conceptions are confused.

At the beginning of The Logic of Scientific Discovery Popper tells us that “the task of the logic of scientific discovery, or the logic of knowledge, [is]… to analyse the method of the empirical sciences” (Popper 1959, 27), and that its first job is “to put forward a concept of empirical science, in order to make linguistic usage, now somewhat uncertain, as definite as possible, and in order to draw a clear line of demarcation between science and metaphysical ideas” (1959, 38-39).