Hume's fork, in epistemology, is a tenet elaborating upon British empiricist philosopher David Hume's emphatic, 1730s division between "relations of ideas" versus "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.