During the period of his academic career, extending from 1747 to 1781, Kant, as has been said, taught the philosophy then prevalent in Germany, which was Wolff's modified form of dogmatic rationalism. That is to say, he made psychological experience to be the basis of all metaphysical truth, rejected skepticism, and judged all knowledge by the test of reason. Towards the end of that period, however, he began to question the solidity of the psychological basis of metaphysics, and ended by losing all faith in the validity and value of metaphysical reasoning. The apparent contradictions which he found to exist in the physical sciences, and the conclusions which Hume had reached in his analysis of the principle of causation, "awoke Kant from his dogmatic slumber" and brought home to him the necessity of reviewing or criticizing all human experience for the purpose of restoring the physical sciences to a degree of certitude which they rightly claim, and also for the purpose of placing on an unshakable foundation the metaphysical truths which Hume's skeptical phenomenalism had overthrown. The old rational dogmatism had, he now considered, laid too much emphasis on the a priori elements of knowledge; on the other hand, as he now for the first time realized, the empirical philosophy of Hume had gone too far when it reduced all truth to empirical or a posteriori elements. Kant, therefore, proposes to pass all knowledge in review in order to determine how much of it is to be assigned to the a priori, and how much to the a posteriori factors, if we may so designate them, of knowledge. As he himself says, his purpose is to "deduce" the a priori or transcendental, forms of thought. Hence, his philosophy is essentially a "criticism", because it is an examination of knowledge, and "transcendental", because its purpose in examining knowledge is to determine the a priori, or transcendental, forms. Kant himself was wont to say that the business of philosophy is to answer three questions: What can I know? What ought I to do? What may I hope for? He considered, however, that the answer to the second and third depends on the answer to the first; our duty and our destiny can be determined only after a thorough study of human knowledge. Freedom plays a central role in Kant’s ethics because the possibility of moral judgments presupposes it. Freedom is an idea of reason that serves an indispensable practical function. Without the assumption of freedom, reason cannot act. If we think of ourselves as completely causally determined, and not as uncaused causes ourselves, then any attempt to conceive of a rule that prescribes the means by which some end can be achieved is pointless. I cannot both think of myself as entirely subject to causal law and as being able to act according to the conception of a principle that gives guidance to my will. We cannot help but think of our actions as the result of an uncaused cause if we are to act at all and employ reason to accomplish ends and understand the world.
The Catholic Encylopedia at New Advent here.
So reason has an unavoidable interest in thinking of itself as free. That is, theoretical reason cannot demonstrate freedom, but practical reason must assume for the purpose of action. Having the ability to make judgments and apply reason puts us outside that system of causally necessitated events. “Reason creates for itself the idea of a spontaneity that can, on its own, start to act–without, i.e., needing to be preceded by another cause by means of which it is determined to action in turn, according to the law of causal connection,” Kant says. (A 533/B 561) In its intellectual domain, reason must think of itself as free. The Internet Encyclopedia of Philosophy here.
I begin with Kant’s 1785 Grounding for the Metaphysics of Morals (1981). The essay’s argument is motivated by Kant’s concern for the dignity of the individual autonomous will, which has worth in itself only because it is an end in itself. Relevant here are two claims Kant makes: autonomy or freedom is necessary for an individual to be a “person,” and this claim admits of no exceptions; that is, any admixture of heteronomy in one’s moral maxims or any treatment by others as anything other than an end in oneself compromises one’s moral personhood.My own view? Beats the heck out of me! I tried reading Kant in Englisch and in German and I did not understand anything. But I do now wonder how accurate and precise was Ayn Rand's view that Kant was evil because he detached the Mind from Reality. She offered a summary, but no direct quotes.
Kantian Individualism and Political Libertarianism by James R. Otteson here