How did Kant attempt to defend the role of reason against skepticism?

Immanuel Kant defended the role of reason against skepticism by initiating a "Copernican revolution" in philosophy, which shifted the focus from how the mind conforms to objects to how objects must conform to the human cognitive apparatus.123

Rather than attempting to derive metaphysical knowledge of things beyond experience—which he argued leads to dogmatism or insoluble contradictions—Kant sought to establish the conditions under which knowledge is possible. He proposed that human knowledge is structured by a priori factors that the mind imposes on the data of experience. Specifically:134

• Sensibility: The faculty of intuition organizes experience through the a priori forms of space and time.13
• Understanding: The mind uses categories—such as causality and substance—to prescribe the necessary order of phenomena.13

By demonstrating that these synthetic a priori judgments are necessary for any coherent experience, Kant vindicated the validity of scientific knowledge while simultaneously setting strict limits on reason. He concluded that reason can only yield valid knowledge of "phenomena" (objects of experience), while the "noumena" (things-in-themselves) remain beyond its reach.5134