Rationalisme

Rationalism, or rationalisme in French, is a philosophical position that regards reason as the primary source of knowledge and justification. It emphasizes a priori knowledge—truths that can be known independently of sensory experience—and often relies on deduction from self-evident principles or clear ideas.

In the 17th century, classical rationalists such as René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz argued that certain fundamental propositions could be known with certainty through reason alone. Descartes developed methodological doubt to identify indubitable foundations and sought to reconstruct knowledge from clear and distinct ideas. Spinoza proposed a coherent deductive system built from axioms, while Leibniz defended the existence of innate notions and of necessary truths discoverable by reason.

Rationalism stood in opposition to empiricism, the view that knowledge primarily derives from sensory experience. The two traditions fueled the central early modern debate about the sources of knowledge. Immanuel Kant later argued that experience provides content, but that the mind contributes a priori concepts and structures that shape our understanding, attempting to synthesize rationalist and empiricist elements.

Rationalism influenced the development of mathematics, science, and metaphysics, and it shaped debates about certainty, necessity, and the nature of ideas. It remains a foundational term in epistemology, used to contrast with empiricism and to describe a family of approaches that emphasize reason's justificatory role.