categories of thought
in the thought of Immanuel Kant, 12 basic concepts of human understanding that are essential to the interpretation of empirical experience. These include such fundamental ideas as unity, plurality, reality, negation, causality, and so on. Although they are necessary to the understanding of sense experience, the categories are themselves a priori rather than empirically given. Time and space play a similar role in ordering one’s sense impressions but are classed by Kant as immediate intuitions rather than categories of thought. The categories are applicable only to the world of appearances or phenomena; there is no reason to suppose that they apply to things-in-themselves (see noumenon).