Kant's Epistemology: Synthetic A Priori Judgments and Metaphysics

Kant's Copernican Revolution and A Priori Knowledge

Kant's work details the conditions under which sciences are established and the requirements that make scientific knowledge universal and necessary. Kant observed, for example, that the progress of physics was produced by a change in perspective. Instead of determining the knowledge of the subject by the object, Kant proposed the opposite (the Copernican Turn), inverting the relationship between the knower and the object known.

Conditions for Scientific Knowledge

Kant sought to investigate the conditions that make scientific knowledge possible. He identified two types of conditions:

• Empirical Conditions: Derived from experience (a posteriori).
• A Priori Conditions: Universal and necessary. These are pre-experiences that do not come from experience but condition it. These conditions are what make experience possible transcendentally.

Kant viewed science as a set of judgments and made a crucial distinction between analytic and synthetic judgments:

• Analytic Judgments: Do not expand knowledge; they are true and necessary (a priori). The predicate is already contained within the subject.
• Synthetic Judgments: Expand knowledge; they are specific and contingent (a posteriori).

The Synthetic A Priori Judgment

Following this distinction, Kant admitted the existence of a third, crucial type of judgment: the synthetic a priori. These judgments are both extensive (expanding knowledge) and universal and necessary.

Science, Metaphysics, and the Limits of Knowledge

Kant began his search for the methodological characteristics of science to compare them with metaphysics and determine if metaphysics truly qualifies as a science. He noted that metaphysics, which studies general being (causes and principles), had failed to secure the reliable path of science.

The problem, according to Kant, is that metaphysics has attempted to make claims about the world without taking into account the experiences and observations we can make. It has tried to speculate about what is beyond phenomena. Kant argues that only what is in the field of phenomena is that of which we may have experience.

Every science must adhere to specific conditions:

• Empirical Conditions: Derived from facts and subject to change.
• A Priori Conditions: Necessary and universal.
• Transcendental Conditions: The a priori conditions that make experience possible.

Every true science must contain synthetic a priori judgments, which are both informative (synthetic) and irrefutable (a priori).

The Role of A Posteriori Judgments

Judgments are categorized by their truth value and source:

• A Priori Judgments: Necessarily true.
• A Posteriori Judgments: Individual, refutable, and contingent (i.e., a single false instance can disprove them).

Kant distinguished between analytic a priori, synthetic a posteriori (informative and compelling), and synthetic a priori judgments. Metaphysics, in contrast, fails this test. Kant denies that metaphysics, as traditionally practiced, can be a science because it attempts to find things (such as the soul, the world as a whole, or God) that are not phenomena—things that can never be accessed through sensitive intuition or pure reason alone. Therefore, Kant concludes that metaphysics must set limits to knowledge.