Kant, Descartes, and Hume: Comparative Philosophy

Relationship between Kant, Descartes, and Hume

Kant's thought can be understood in relation to other philosophers, such as R. Descartes and D. Hume. A comparison between Descartes and Kant reveals key differences in their approaches to epistemology.

Descartes vs. Kant

Descartes, in his quest to understand knowledge, prioritized ideas meeting the criteria of clarity and distinction, effectively dismissing empirical data derived from the senses. He believed only mathematical and metaphysical truths met this standard. Descartes' method of doubt aimed to establish a foundational principle for all human knowledge, not solely mathematical knowledge.

Kant, with his central question, "What can I know?" (addressed in the *Critique of Pure Reason*), similarly sought to define the origin, nature, and limits of human knowledge. Like Descartes, he searched for a solid foundation for philosophy and science. However, Kant found the rationalist response insufficient.

In his *Critique of Pure Reason*, Kant examines the conditions that enable science and questions whether metaphysics can be considered a science. He posits that while some concepts originate from experience (contrary to pure empiricism), these concepts are only applicable within the realm of experience (contrary to pure rationalism). He concludes that metaphysics, as a science, is impossible because categories can only be applied to phenomena. Metaphysical concepts (God, Soul, World, Liberty) lie beyond phenomenal experience.

Hume vs. Kant

Kant's work should also be contrasted with the solutions offered by British empiricism, particularly the work of D. Hume. Hume also aimed to clarify the limits of human knowledge. He argued that the contents of the human mind, which he termed "perceptions," are of two types: impressions and ideas. Ideas are copies, memories, or images of impressions, which originate directly from experience.

For Hume, only ideas that adhere to the "copy principle"—possessing a clear referent in experience—are valid. Consequently, he rejects metaphysics, viewing it as obscure, dogmatic, and conducive to superstition. Kant acknowledged that reading Hume awakened him from his "dogmatic slumber" and concurred that metaphysics cannot be a science.

However, Kant diverges from empiricism, asserting that the intellect spontaneously generates certain concepts *not* derived from experience, such as cause, necessity, and substance. The concept of cause highlights a significant difference between Hume and Kant.

Hume denied the possibility of knowing causal connections in the future, as we lack experience of events that haven't occurred. Therefore, we must rely on probabilities based on habit and custom. Kant, in contrast, argued that Hume conflated particular laws with the general principle of causality. Kant uses this example: suppose, according to a law, bodies expand when heated. If an exception occurs and a body contracts, this wouldn't violate the *universal* principle of causality (which states that everything that begins to exist has a cause). Instead, it would be an exception to a *particular* law; the contraction would still have a cause, upholding the principle of causality.

Furthermore, Kant enriched Hume's distinction between *relations of ideas* (analytic propositions) and *matters of fact* (synthetic statements) by asserting that the propositions of mathematics and physics are *synthetic a priori* (both informative and universally and necessarily true).

Another crucial difference is that Kant shifts the focus of inquiry from the *object* of knowledge (ideas for rationalists, sensory perception for empiricists) to the *subject*. The human being is the active element that contributes their own structure to knowledge. The object is only known insofar as humans can integrate it into their cognitive system (a pivotal shift in philosophy).