Immanuel Kant accepts David Hume’s view that all knowledge arises from experience, but he goes on to note that it is wrong to say that because our knowledge arises from experience, it is grounded in experience. In his theory of causal concepts, Hume posits that we know that X is the cause of Y when from our experience we see that X and Y are together. In Kant’s philosophy, the cognitive holdings that are not the result of experience, or are non-empirical, are referred to as “pure.”
In his Critique of Pure Reason, Kant conducts a critical examination of the forms of rationality that are non-empirical (or not based on experience) and whose purpose is to create the framework in which all experience can become possible. Kant notes that without the intuitions of “time” and “space” experience is not possible. From here he goes on to develop the concept of pure intuitions of “time” and “space.” In Kantian terminology, an intuition is a necessary precondition for any form of experiential knowledge to develop. It would be illogical to say that this precondition is developed after the experience—it has to be prior to all experience (Kant calls it a priori), or there will be no experience.
To prove that knowledge can be said to arise out of experience but may not be grounded in experience, Kant offers a view of the framework of all knowledge (in his “Analytic of Concepts”). He says that every instance of knowledge involves a judgement which is formed within a universal categorical framework that includes entities that could not have come from experience. He offers twelve pure concepts, or “Pure Categories of the Understanding,” which are divided into four categories of three. He says that these categories of understanding could not have come from experience and would admit no exceptions. The categories are:
Quantity: Unity, Plurality, Totality
Quality: Reality, Negation, Limitation
Relation: Inherence and Subsistence, Causality and Dependence, Community
Modality: Possibility, Existence, Necessity
According to Kant, these categories are the necessary conditions for knowledge of anything in the universe. He sees the pure intuitions as the necessary forms of experience, and the pure categories as the necessary forms of knowledge.