Alternative theories play an important role in Paul Feyerabend’s conception of methodology. Because facts and theories are inextricably entwined, even apparently false and unsuccessful theories can play a vital constructive role in theory evaluation (see, for example, Feyerabend 1975/1988, p. 33). Competitor theories can draw attention to hitherto unnoticed facts. And some facts are even wholly undetectable without the aid of an alternative theory. In response to the new facts, proponents of competing theories are pressed to either (i) accept the new theory that exposed the new facts or (ii) develop the accepted theory to account for the new facts. This is one of the important ways in which science progresses. Our theoretical understanding of the world is thus enriched by theoretical pluralism.