ORIGINS

Although Kant introduced many pieces of technical terminology to articulate the themes of his critical philosophy, perhaps none is more pervasive than “a priori.” The initial care, and apparent precision, with which the termenters the Critique of Pure Reason quickly gives way to profligacy, as all sorts of things come to be hailed as a priori. My aim in this essay is to bring some order to Kant's many-sided usage.

One source of Kant's conception is evident. Many of his predecessors had recognized that there are apparently items of human knowledge that do not rest upon our everyday processes of sensory observation, and had supposed that there must be other sources that deliver knowledge of these types. In the more ambitious versions of this idea, there is a rich collection of “truths of reason,” among which earlier philosophers had sometimes counted controversial metaphysical principles, as well as generalizations they took to be fundamental to nascent physical science.

Even those most firmly committed to empiricism, and to the thesis that human knowledge is based upon sensory observation, made a place for something like a priori knowledge. The classical British Empiricists were unwilling to grant that our knowledge of logical truths and of the principles of mathematics – by which they understood basic arithmetical identities and Euclidean geometry – is justified by some process of sensory experience.