How did Kant’s philosophy combine rationalism with skepticism?

Immanuel Kant’s philosophy, known as transcendental idealism, synthesized rationalism and skepticism by reorienting the relationship between the human mind and the world.12

Kant addressed the skepticism of David Hume—who argued that causality and other necessary connections could not be proven—by shifting the focus from whether knowledge is possible to how it is possible.13

• Rationalist Element: Kant argued that the mind is not a passive recipient of data but actively constructs knowledge. He posited that human experience is structured by a priori "forms" of sensibility (space and time) and "pure concepts of the understanding" (such as causality and necessity). These universal conditions allow for genuine scientific knowledge within the realm of experience.123
• Skeptical Element: Kant maintained a strict skepticism regarding metaphysics. He asserted that we can only know phenomena (things as they appear to us). We can never know things-in-themselves (noumena), which exist independently of our minds and are beyond the reach of human reason.143

While theoretical knowledge of God, freedom, and immortality is impossible, Kant argued these are necessary postulates for moral agents, bridging the gap between his epistemology and ethics.145