The hypothesis that saves the day: ad hoc reasoning in pseudoscience

What is wrong with ad hoc hypotheses? Ever since Popper’s falsificationist account of adhocness, there has been a lively philosophical discussion about what constitutes adhocness in scientific explanation, and what, if anything, distinguishes legitimate auxiliary hypotheses from illicit ad hoc ones. This paper draws upon distinct examples from pseudoscience to provide us with a clearer view as to what is troubling about ad hoc hypotheses. In contrast with other philosophical proposals, our approach retains the colloquial, derogative meaning of adhocness, and calls attention to the way in which the context of a theoretical move bears on the charge of adhocness. We also discuss the role of motivations implicit in the concept of adhocness, and the way ad hoc moves draw on theory-internal rationalizations.