Kant’s Transcendental Idealism: A Summary
Kant’s Transcendental Idealism
Intuition and Sensibility
Kant defines intuition as the immediate relation between subject and object of knowledge. The subject possesses a priori forms of sensibility: space and time. These reorder data received through the senses.
Space is the form of outer sense, while time is the form of inner sense. Everything is perceived within space and time. However, space and time are not objective realities, but forms imposed by the subject onto impressions. Sense impressions framed in space and time are called empirical intuitions.
A priori elements in sensibility explain the existence of geometry and arithmetic:
- Geometry: Based on the pure study of space. Its judgments are universal, pre-experiential, and provide essential information. These are synthetic a priori judgments.
- Arithmetic: Based on temporal intuition. Its judgments are also synthetic a priori.
Transcendental Logic: Transcendental Analytic
Transcendental Analytic studies the concepts that structure understanding. Understanding synthesizes representations from sensibility using concepts. Kant distinguishes between pure concepts (categories) and empirical concepts.
Categories are a priori forms of understanding that allow us to think about sensible intuitions. This means:
- Categories are the condition of possibility for sensible intuitions.
- Categories only apply to sensible intuitions. Any other use is illegitimate and leads to errors.
Thinking and intuition are interdependent. Intuitions must be thought by the intellect, and understanding cannot operate without intuitions. The result of sensing reality and thinking through categories is the phenomenon.
Physics is a science because its judgments are based on categories applied to sensible intuitions, resulting in synthetic a priori judgments. Categories like causality cannot be applied to non-phenomenal realities, as that would be an illegitimate use.
The noumenon, or thing-in-itself, is reality before human cognition. It is the limit of experience—the external reality that makes knowledge possible but cannot itself be known. The noumenon is what remains when categories and spatiotemporal intuitions are removed from the phenomenon.
Transcendental Logic: Transcendental Dialectic
Transcendental Dialectic shows that metaphysics is not a science. Reason investigates the causes and basis of reality, leading to three ideas: soul, world, and God.
These ideas transcend experience and have a regulatory function. However, treating them as objects leads to illegitimate use and contradictory statements. The three ideas give rise to three branches of metaphysics: rational psychology (soul), cosmology (world), and theology (God).
- Rational Psychology: The idea of the soul leads to questions about its nature, but this is a misuse of reason.
- Cosmology: The idea of the universe as a unit leads to contradictions when treated as an objective reality.
- Theology: The idea of God as the foundation of reality leads to illegitimate attempts to prove God’s existence, such as:
- Physico-teleological arguments: Concluding God’s existence from the world’s order is illegitimate, as phenomenal matters cannot lead to transcendent realities.
- Cosmological arguments: Arguing for a necessary being (God) based on the world’s contingency is also illegitimate.
- Ontological arguments: Attempting to prove existence from a concept confuses logical and ontological planes.
In conclusion, synthetic a priori judgments about the soul, world, or God are impossible because they are transcendent ideas of reason. Kant doesn’t deny their possible existence, but argues that we cannot prove it because they are not phenomena.