Kant’s Critique of Pure Reason: Structure and Key Concepts
Critique of Pure Reason (CPR): Kant’s seminal work examines the nature, role, and limits of human reason. The primary problem addressed is the rational foundation of metaphysics. Despite being considered the mother of all sciences, metaphysics faces challenges in being demonstrated through rational methods comparable to natural sciences or mathematics. Kant argues that metaphysics often relies on a priori concepts lacking universal validity and derived from simple concepts and trial-and-error approaches. Consequently, he deems it an invalid form of knowledge. He concludes that attempts to establish a metaphysical knowledge base have failed and proposes a ‘Copernican turn’ in philosophy: instead of the object dictating the subject’s understanding, the subject shapes the object’s perception; reality conforms to human understanding. This concept, known as transcendental idealism, synthesizes rationalism and empiricism. Kant asserts that objects, or rather experience, possess a priori rules that precede and shape our understanding of them.
CPR Part 3: Sensibility and the A Priori
The Critique of Pure Reason is divided into three parts. The first concerns the conditions for perceiving objects: vision, perception, orientation, and observation of nature depend on two necessary and universal conditions: space and time. These are the a priori forms of sensibility.
Space and time as a priori forms of sensibility:
- Forms-means: Space and time are not about specific sensory inputs (colors, sounds, etc.) but rather the way we perceive all impressions. Colors, sounds, and movements are all perceived within space and time.
- A priori: Their validity doesn’t depend on experience but exists prior to it. Space and time are not derived from experience but are the preconditions that make experience possible.
- Of sensibility: They pertain to all sensory knowledge. Kant distinguishes between inner and outer sensibility. Outer sensibility is subject to space and time, while inner sensibility is subject only to time (series of experiences, imaginations, memories, etc.).
Space and time can be understood as pure intuitions.
CPR Part 1: The Problem of Knowledge
Kant formulates the question: How do we come to know objects? There are two possibilities:
- The subject produces its object of knowledge (rationalism). The subject follows reality and draws conclusions from ideas in the mind.
- The object is passively received by the subject (empiricism).
Kant argues that a priori knowledge is necessary but not always universal and objective, while objective knowledge is acquired through experience but is universal and necessary. He seeks a solution that provides knowledge that is both universal and necessary, similar to Newton’s objectively necessary and universal science. The Critique of Pure Reason aims for a critical analysis of our reason. Kant believed that Hume’s position was inadequate and that empiricism was not the definitive solution, stating, “Reason without experience is empty, experience without reason is blind.”
CPR Part 2: The Copernican Revolution in Epistemology
True knowledge, according to Kant, arises from a combination of reason and experience. He describes his theory of knowledge as a “Copernican revolution,” arguing that the mind should not conform to objects to know them, but rather objects should conform to our minds. He proposes that objects should be governed by our knowledge, allowing for the possibility of a priori knowledge. This implies that we cannot know objects in themselves but only as they appear to us, as our minds actively shape the process of knowledge. Kant identifies synthetic a priori judgments as the basis for knowledge in mathematics, physics, and metaphysics.
- Analytic and Synthetic Judgments: A judgment is analytic if the predicate is already contained within the subject (e.g., “All bachelors are unmarried”). It doesn’t expand our knowledge. A synthetic judgment adds new information (e.g., “The table is heavy”).
- A priori and A posteriori Judgments: An a priori judgment is known independently of experience (e.g., mathematical truths), while an a posteriori judgment is known through experience (e.g., “The sky is blue”).
- Synthetic A priori Judgments: Kant argues for the existence of synthetic a priori judgments, which expand our knowledge of reality and are universally valid.