Autonomie – Metaphysik – Endlichkeit: Die Endlichkeit menschlichen Denkens bei Kant

It is often maintained that German Enlightenment philosophy—and especially the Enlightenment program that Immanuel Kant articulated in his famous article in the Berlinische Monatsschrift—is not able to do justice to the role of testimonial knowledge and hence is an obstacle to a down-to-earth epistemology because of its essential individualistic stance. I argue that this is a misunderstanding and that Kant like other Enlightenment thinkers actually recognizes these social factors and their impact on our knowing and thinking. I show that Kant's philosophy can be reconstructed as an attempt to show the compatibility of Enlightenment's demand for independence and the essential dependency of finite cognizers. His mature philosophy aims at developing a kind of Enlightenment Ethics of Belief that can be found in the final sections of his Critique of Pure Reason.
The central task of (a Kantian conception of) Enlightenment points to intellectual independence, the thinking for oneself and the spontaneous activity of our own intellectual faculties that is not ruled by others but only by ourselves. Now this activity should consist of the actualization of the common faculty of reason and not in arbitrary decision making to believe one thing over another. Thinking for oneself thus seems to be the outcome of a competence rather than the result of a mere decision. This is an insight which was famously defended by Christian Wolff. While Wolff claims that this competence is to be understood as being able to follow some special method—the mathematical method—Kant points to the social character of thinking. Thinking for oneself means competently reasoning in accordance with rules that can only be followed and assessed through conversational practice.
How is this demand for maturity affected by our finiteness? To answer this question it is necessary to give a clear concept of our finiteness. According to Kant, the core of our finiteness as human beings consists in our dependency on being passively affected: on cognizing things with our senses instead of through pure reason or by what we are told. We cannot cognize things without being affected by them; all that we know by pure reason alone are very general truths (for instance, things happen in accordance to natural laws). The terminus technicus for this concept is discursivity which is the property of concepts that distinguishes them from intuitions. A concept is a representation that is discursive which means that it is mediately related to its objects via universal marks and is hence a universal representation. Intuitions on the other hand are immediately related to their objects and are hence singular representations. Our understanding is discursive because it is a faculty of thinking which cognizes objects through concepts that are dependent on a faculty of intuitions to relate to objects. Without such intuitive, i.e., immediate relations our understanding would have no content at all.
Most work on testimonial knowledge focuses on the trustworthiness and competence of the speaker. Although Kant addresses such topics, these are rather secondary reflections unsuited to be an adequate foundation for understanding of the compatibility of intellectual independence and the dependency on others. In freely following Wolff, Kant distinguishes in a first step between rational and historical cognitions. A cognition is rational if it is generated by the cognizer's own use of his pure reason, otherwise it is historical, i.e. it is given to him by his senses or the words of others. In a second step he makes a difference between rational and empirical cognitions, the latter being cognitions that can only be known historically. While the distinction between rational and empirical cognitions signifies a difference in their very character, the difference between rational and historical cognitions means a difference in our own personal access to them. (In a further step he distinguishes between discursive rational cognitions in philosophy and intuitive rational cognitions in mathematics, but this is of lesser importance than the first distinction.) The point is that different kinds of cognitions are to be treated in different ways. Having a critical stance toward testimonial knowledge means that we should not accept rational cognitions on the grounds of being told.
Knowingly diverging from his predecessors, Kant defines metaphysics as the system of rational cognitions, i.e. the systematically ordered body of knowledge we gained through pure reason. Thus metaphysics is the discipline that does not allow for just historical cognitions. Now to Kant philosophy is not—as it has been for Wolff and others—the whole body of science besides mathematics, but is rather identical with metaphysics. Summarizing all these results we can assign a reason for why we should learn philosophizing rather than philosophy: It is because metaphysics is a rational discipline that we cannot learn by acquiring merely historical knowledge but only by learning to use our own faculty of reason.