Hume's fork

Hume's fork, in epistemology, is a tenet elaborating upon British empiricist philosopher David Hume's emphatic, 1730s division between "relations of ideas" and "matters of fact." (Alternatively, Hume's fork may refer to what is otherwise termed Hume's law, a tenet of ethics.) As phrased in Immanuel Kant's 1780s characterization of Hume's thesis, and furthered in the 1930s by the logical empiricists, Hume's fork asserts that all statements are exclusively either "analytic a priori" or "synthetic a posteriori," which, respectively, are universally true by mere definition or, however apparently probable, are unknowable without exact experience. By Hume's fork, a statement's meaning either is analytic or is synthetic, the statement's truth—its agreement with the real world—either is necessary or is contingent, and the statement's purported knowledge either is a priori or is a posteriori. An analytic statement is true via its terms' meanings alone, hence true by definition, like Bachelors are unmarried, whereas a synthetic statement, concerning external states of affairs, may be false, like Bachelors age badly. By mere logical validity, the necessary is true in all possible worlds, whereas the contingent hinges on the world's state, a metaphysical basis. And the a priori is knowable without, whereas the a posteriori is knowable only upon, experience in the area of interest. By Hume's fork, sheer conceptual derivations (ostensibly, logic and mathematics), being analytic, are necessary and a priori, whereas assertions of "real existence" and traits, being synthetic, are contingent and a posteriori. Hume's own, simpler, distinction concerned the problem of induction—that no amount of examination of cases will logically entail the conformity of unexamined cases—and supported Hume's aim to position humanism on par with empirical science while combatting allegedly rampant "sophistry and illusion" by philosophers and religionists.