Kant's Critique of Pure Reason: Metaphysics and Human Understanding

The Problem of Metaphysics

In metaphysics, critical reason seeks to understand the reality of the speculative or theoretical, apart from sensory experience. Kant observed that this discipline was barely progressing, often regressing, and dominated by disagreements. He attributed this to the dogmatism of some philosophers and the skepticism of others. To resolve this impasse, Kant undertook a metaphysical inquiry that was critical rather than dogmatic.

Kant addressed the problem of metaphysics by distinguishing between scientific knowledge, moral philosophy, and dogmatic metaphysics. This distinction led to three consequences:

• The possibility of metaphysics as a theory about the foundations of knowledge and science.
• The possibility of metaphysics as a set of moral beliefs required for practical reason.
• The impossibility of science knowing metaphysical realities beyond experience. Metaphysics is not knowledge, much less science, but an illusion.

The Inevitability of Metaphysical Illusion

This illusion is not accidental; it is inevitable because it originates in the very nature of human reason, which, according to Kant, always tends toward metaphysics. Hence, the need for a critique of reason. Kant identified two faculties of knowledge: sensitivity and understanding. However, he distinguished a third faculty in humans: reason. Reason is not a faculty of knowledge but rather a faculty for systematizing knowledge, providing unity. This is a requirement of human reason, which is not satisfied by any experience.

Reason's Operations and the Three Ideas

Reason, in its operations, which Kant called "Ideas," fulfills this vocation for generality. Because Ideas are very general concepts, beyond all possible experience, they synthesize sequences of conditioned phenomena. Reason traces the series of phenomena, identifies a number of conditions, jumps over them, and locates itself in the unconditioned. It then develops an Idea that summarizes the terms of the multiplicity of paths.

Kant identified three Ideas of reason, corresponding to the three major issues of metaphysics:

• Soul: Reason thinks of the substantial unity of the subject.
• World: The Idea of the world is the unity of all phenomena.
• God: The Idea of God is the unity, in a supreme synthesis, of all objects of thought and is the foundation of the other two Ideas.

The Legitimate Function of Ideas

For now, these Ideas are legitimate; they are requirements of our reason. They are just Ideas that do not imply the existence of corresponding content. Ideas function as ideal limits, regulating scientific research. Metaphysics has not yet begun.

The Illusion of Applying Categories to Ideas

Humans cannot think without categories. From the moment that reason produces the most general Ideas, it operates with categories. When these categories are applied to experience, the illusion occurs that specifies the metaphysics of the world, soul, and God as things in themselves and not mere Ideas, mere limits, or horizons in research. This illusion is almost inevitable from the moment reason produces Ideas and understanding cannot think without categories.