quality:corruption, structural:summarization, linguistic:translation, information:extraction, quality:correction
Early uses

The term a priori is Latin for 'from what comes before' (or, less literally, 'from first principles, before experience'). In contrast, the term a posteriori is Latin for 'from what comes later' (or 'after experience').

They appear in Latin translations of Euclid 's Elements, a work widely considered during the early European modern period as the model for precise thinking.

An early philosophical use of what might be considered a notion of a priori knowledge (though not called by that name) is Plato 's theory of recollection, related in the dialogue Meno, according to which something like a priori knowledge is knowledge inherent, intrinsic in the human mind.

Albert of Saxony, a 14th-century logician, wrote on both a priori and a posteriori.

The early modern Thomistic philosopher John Sergeant differentiates the terms by the direction of inference regarding proper causes and effects. To demonstrate something a priori is to "Demonstrate Proper Effects from Proper Efficient Causes" and likewise to demonstrate a posteriori is to demonstrate "Proper Efficient Causes from Proper Effects", according to his 1696 work The Method to Science Book III, Lesson IV, Section 7.

G. W. Leibniz introduced a distinction between a priori and a posteriori criteria for the possibility of a notion in his (1684) short treatise "Meditations on Knowledge, Truth, and Ideas". A priori and a posteriori arguments for the existence of God appear in his Monadology (1714).

George Berkeley outlined the distinction in his 1710 work A Treatise Concerning the Principles of Human Knowledge (para. XXI).