"Apriori" redirects here. For other uses, see Apriori ."A posteriori" redirects here. For the Enigma album, see A Posteriori.The terms "a priori" and "a posteriori" are used in philosophy to distinguish between deductive and inductive reasoning, respectively. Attempts to define clearly or explain a priori and a posteriori knowledge are part of a central thread in epistemology, the study of knowledge. Since the definitions and usage of the terms have been corrupted over time and therefore vary b