Critique of Pure Reason: Exploring the Limits of Human Knowledge
Analysis of Human Reason
Human reason is constantly challenged by questions that extend beyond its grasp, particularly those raised by metaphysics. Kant explored whether understanding can create a universally valid science. Influenced by Hume, Kant recognized the importance of experience and distinguished between empirical and formal conditions of knowledge. He questioned the nature of metaphysics as a science, noting that scientific knowledge progresses through consensus and builds upon previous work. If metaphysics were a science, it should develop like logic or mathematics. Kant proposed a “Copernican revolution” in method: “we only know a priori of things that we put ourselves into them.” This implies that our knowledge isn’t governed by things, but rather things are governed by our way of knowing. Kant divided reality into the phenomenon (the world as experienced through the senses) and the noumenon (the thing itself, unknowable).
The Theory of Judgments
Science consists of judgments, which can be analytical (universal and necessary but not extending knowledge), synthetic (extending knowledge but not necessarily a priori), or synthetic a priori (judgments whose truth can be known without experience). Kant argued that only synthetic a priori judgments can be scientific and advance knowledge. To determine if metaphysics is possible as a science, he questioned the possibility of synthetic a priori judgments in metaphysics, applying his doctrine to the powers of human knowledge.
Transcendental Aesthetics (Sensitivity)
Kant explored how synthetic a priori judgments are possible in mathematics. He posited that space and time are a priori conditions of objectivity, enabling such judgments. Space is a pure intuition, a form of a priori knowledge that is not mere opinion. Intuition is a direct apprehension of individuality. Knowledge requires certain conditions met by the knower. The subject acts upon something, making it an object of knowledge. These are the transcendental conditions of objectivity. Nothing can be an object of knowledge unless it exists in space, making space an a priori form of external sensibility. Time is an a priori form of internal sensibility, relating to the succession of our inner experiences. It is the basis of all experience and pure intuition. Through these a priori forms, sensory perceptions are formalized and become phenomena.
Transcendental Analytic (Understanding)
Kant then questioned how synthetic a priori judgments are possible in physics. He studied understanding to identify the a priori forms that allow intellectual knowledge. The world of phenomena is known as the physical or objective world. Kant distinguished this phenomenal world from the noumenal world, which is transcendent and unknowable. Objectivity is to be defined by a predicate in a judgment. There are as many forms of objects as there are possible judgments. Following Aristotle, Kant identified twelve categories based on quantity, quality, relation, and modality.
Transcendental Dialectic (Reason)
This central theme explores the parameters of science. Kant questioned whether synthetic a priori judgments are possible in metaphysics. He elucidated transcendental illusions, subjective principles presented as objective, arguing that pure reason produces these illusions. All knowledge begins with the senses, proceeds through understanding, and culminates in reason. Reason has two uses: pure logic and practical use. Logic helps reason synthesize knowledge from the understanding. There are three types of reasoning: categorical, hypothetical, and disjunctive, leading to three types of synthesis. However, reason never achieves a complete synthesis. The temptation is to create a total synthesis using pure concepts of reason, which Kant calls ideas. Transcendental ideas are reduced to three: the self, the world, and God. Reason is a synthesizing power, legitimate when applied to experience. However, it can make judgments beyond experience. These are based on the idea that every phenomenon is conditioned by a previous one and conditions a subsequent one. The category of “cause and effect” makes each event both a condition and conditioned. Reason seeks something unconditioned. This illegitimate leap is the illusion of pure reason. Kant argued that metaphysics is a set of illusions. The concept of the soul cannot be scientific because it’s constructed by omitting time, a condition of intelligibility. He also rejected the rational construction of the metaphysics of the universe and natural theology. He argued that attempts to scientifically prove God’s existence are false. The transcendental dialectic results from wanting to know more than experience allows. These three syntheses cannot be experienced within the phenomenal world; they belong to the unknowable noumenal world. For something to be knowable, we must apply our a priori forms of sensibility. Because these objects cannot be experienced, they cannot be known. Kant acknowledged that these ideas of pure reason are a priori forms of reason itself. By denying metaphysics, Kant didn’t deny the existence of metaphysical realities. He believed he’d removed the problem of scientifically proving their existence. Another activity of consciousness is not rational knowledge. Kant found solace in other paths to understanding God, seeing God as a necessary postulate.