A prio'ri.

A prio'ri. A priori reasoning, in Kant's use of the term, is that which rests on general notions or ideas, and is independent of experience; which is derived from the constitution of the mind, and is accordingly prior to all experience. But the word is used loosely in various senses; sometimes for reasoning from a general principle to its consequences; sometimes from observed facts to another fact or principle not observed; still more loosely for arguing from pre-existing knowledge, or even from cherished prejudices ('innate ideas' would be a priori). The Aristotelian usage made a priori reasoning from cause to effect; a posteriori from effect to cause. Now usually, reasoning from experience is called a posteriori reasoning. A predilection for one or the other of these forms of reasoning forms one of the most important distinctions among schools of philosophy. Plato and most of the great Germans may be taken as typical of the a priori school, Bacon and Locke of the empirical or experimental. A priori philosophy claims for its conclusions the character of necessary truths, and denies that there can be a posteriori proof of anything, that kind of reasoning furnishing only a confirmation or verification. The opposite school maintain that the general notions or principles on which a priori reasoning rests are themselves the results of experience, and that, therefore, all truth rests really on a posteriori grounds. Synthetic and analytic, deductive and inductive, correspond in a general way to a priori and a posteriori. See ANALYSIS, DEDUCTION, INDUCTION, LOGIC, TRANSCENDENTALISM.