I take pseudoscience to be a pretence at science. Pretences are innumerable, limited only by our imagination and credulity. As Stove points out, ‘numerology is actually quite as different from astrology as astrology is from astronomy’ (Stove 1991, 187). We are sure that ‘something has gone appallingly wrong’ (Stove 1991, 180) and yet ‘thoughts…can go wrong in a multiplicity of ways, none of which anyone yet understands’ (Stove 1991, 190). Often all we can do is give a careful description of (...) a way of pretending, a motivation for pretence, a source of pretension. In this chapter I attempt the latter. We will be concerned with the relation of conviction to rational belief. I shall be suggesting that the question of whether an enquiry is a pretence at science can be, in part, a question over the role of conviction in rational belief, and that the answer is to be found in the philosophical problem of the role of values in rational belief. (shrink)