Strenger, as both practising clinical psychologist and philosopher, is singularly well placed to ask such epistemological questions as: what type of knowledge is psychoanalytic knowledge? Does it belong with the natural sciences, or is it a purely hermeneutic discipline which need not bother with controlled research since it deals with meanings and not with causes? The strengths and weaknesses of the forms of thought underpinning psychoanalytic ‘reasoning’ are examined and evaluated.