1. (n.) A supposition; a proposition taken for granted, in order to draw a conclusion\ or inference for proof of the point in question; something not proved, but assumed for the purpose of argument, or to account for a fact or an occurrence; as, the hypothesis that head winds detain an overdue steamer.

2. (n.) A tentative theory or supposition provisionally adopted to explain certain facts, and to guide in the investigation of others; hence, frequently called a working hypothesis.

a priori principle affirmation apriorism assertion assumed position assumption axiom basis categorical proposition conjecture data first principles foundation ground guesswork hypothesis ad hoc inference lemma major premise minor premise philosopheme philosophical proposition position postulate postulation postulatum premise premiss presumption presupposal presupposition proposition propositional function set of postulates speculation statement sumption supposal supposing supposition surmise theorem theory thesis truth table truth-function truth-value working hypothesis