 Kuhn disliked being compared to Hegel, whose work he found obscure and characterized by a non-naturalistic philosophy of history, but it is worth commenting further on the partial resemblance. Both Kant and Hegel rejected naïve empiricism, according to which all human knowledge arises, somehow, from the accumulative aggregation of individual sensations or perceptions. Kant argued that we need transcendental structures such as a system of processing rules in order to organize sensory input into something coherent and intelligible, e.g., as physical objects interacting causally in space and time. These were Kant’s forms of intuition (in space and time) and categories (substance, causality, etc.). They represent the human mind’s contribution to knowledge. (In this regard Kant can be regarded as a forerunner of cognitive psychology.) Thus, our experience of the world is shaped to fit a priori forms, and this is where the Kantian version of idealism enters the picture: the world of human experience is not the world of ultimate reality (Kant’s unknowable, noumenal world of things-in-themselves); rather, it is a world shaped by our own cognitive structures.