a priori

a term originating from the work of Immanuel Kant (1724-1804) referring to any knowledge which is known to be true independently of experience. It contrasts with a posteriori which refers to knowledge confirmed by observation. Kant attempted to distinguish analytic a priori statements - true by reason of definition - from the synthetic a priori which are necessarily true statements but which are informative about experience, such as statements in mathematics or the statement 'every event must have a cause'. Synthetic a priori statements are said to be never false in any logically possible world.