Kant’s Theory of Knowledge: Phenomena, Noumena, and the Limits of Reason
Kant’s Theory of Knowledge
Synthetic A Priori Judgments
The principle that the sum of the angles of a triangle equals 180 degrees is a synthetic judgment a priori. The concept of the sum of internal angles doesn’t inherently contain the specific number 180. This principle is necessary and universal, applying to every triangle.
Physics, the study of natural laws, explores the dynamics of all things. Nature, determined by these laws, represents the essence of things. However, if nature signified the essence of things-in-themselves, we could never know it, neither a priori nor a posteriori. How can we know the reality of a thing beyond our concept of it? Experience provides only isolated cases, insufficient for deriving universal laws. Yet, knowing these laws a priori also requires experience as a factor in understanding relations between things.
Physics utilizes mathematics (constructed from synthetic judgments a priori) and concepts (which are analytical). The formula for speed (v = d/t) is a synthetic proposition a priori. The concept of speed isn’t contained within the concept of distance multiplied by time. It’s a priori because it’s necessary; a car traveling at a constant speed of 50 kilometers per hour will inevitably travel 50 kilometers in one hour.
If physical laws don’t belong to objects themselves and are synthetic and a priori, how can they determine actual experience? Theoretical propositions of pure reason (like those in mathematics and physics) have universal validity because they determine not experience itself, but the possibility of experience. Objective knowledge requires an object of reference. Without it, concepts are empty. An object, to be understood, must be exposed to intuition, whether real or possible. The possibility of experience gives objective reality to a priori knowledge.
Metaphysics: Phenomena and Noumena
The noumenon, in Kant’s philosophy, refers to an object not belonging to sensible intuition but to a supersensible, intellectual intuition. Phenomena constitute the world as we perceive it, while noumena represent the world independent of our experience—the “thing-in-itself.” Humans can only know things as experienced, not things-in-themselves. Philosophy, therefore, must focus on understanding the process of experience.
This concept influenced phenomenology (Hegel, Husserl, Heidegger, Derrida), psychodynamic models in psychology, and theories about brain-mind-world interaction. The term “noumenon” has also been used to denote things-in-themselves, independent of any representation.
Negative Sense of Criticism: Reason Limited to Phenomena
Theoretical science of reason, based on reason and verified by experience, includes pure mathematics (arithmetic and geometry) and theoretical physics. These forms of knowledge are considered infallible. The proposition 2 + 2 = 4 is apodictic. While seemingly analytic, it’s actually synthetic. The concept of 2 + 2 implies a sum, not specifically 4. The result is new knowledge.
A more complex example, like 25,164 + 59,468, clarifies this. We know the sum will be a number, but not the specific number. The proposition is synthetic because the result is new knowledge. However, it’s also a priori because the result is necessarily the same every time. Mathematical propositions are a priori, not empirical, due to their inherent necessity.
Geometry also employs synthetic judgments a priori. The statement “the shortest distance between two points is a straight line” is synthetic because the concept of “straight” doesn’t contain the concept of magnitude (“shortest”). It’s a priori because it’s a necessary truth for any two points in space.