I presently find that as I cannot think anything without a category, I must first look for a category for the rational idea of freedom with which I am now concerned; and this is the category of causality; and although freedom, a con- cept of the reason, being a transcendent concept, cannot have any
corresponding to it, yet the concept of the understanding- for the synthesis of which the former demands the unconditioned-- (namely, the concept of causality) must have a sensible intuition given, by which first its objective reality is assured.
The-Critique-of-Practical-Reason-The-Metaphysical-Elements-of-Ethics-and-Fundamental-Principles-of-the-Metaphysic-of-Morals-by-Immanuel-Kant
