 In his meta-methodology, Feyerabend applied to the dispute over the interpretation of scientific theories a strong measure of Popperian methodological conventionalism, arguing that the dispute between realists and instrumentalists is not a factual issue but a matter of choice. We can choose to see theories either as descriptions of reality (scientific realism) or as instruments of prediction (instrumentalism), depending on what ideals of scientific knowledge we aspire to. Adherence to these competing ideals (roughly: high informative content on the one hand, and sense-certainty on the other) is to be judged by their respective consequences. Stressing that philosophical theories have not merely reflected science but have changed it, Feyerabend argued further that the form of our knowledge can be altered to fit our ideals. So we can have certainty, and theories that merely summarise experience, if we wish. But, mobilising the usual equation between empirical content and testability (common to Carnap, Popper and Feyerabend), he urged that we should decisively reject the ideal of certainty and opt instead for theories which go beyond experience and say something informative about reality itself. In this respect, he clearly followed Popper’s lead, reconstruing empiricism as a doctrine about the most desirable form for our theories, rather than as a view about the sources of knowledge.