rationalism

Rationalism is a philosophical position that attributes primary authority to reason in the acquisition of knowledge, often in contrast with empiricism, which emphasizes sensory experience. Rationalists contend that there are substantial areas of knowledge that are a priori, necessary, and not derived from observation. They frequently suppose that some ideas are innate or built into the mind’s structure, or at least accessible through rational reflection and deduction.

In the modern era, rationalism is associated with a trio of 17th-century thinkers: René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz. Descartes developed a method of doubt aimed at securing certain knowledge and argued that the mind contains clear and distinct ideas that yield foundational truths, such as the cogito, “I think, therefore I am.” Spinoza pursued a systematic metaphysical unity rooted in reason, while Leibniz defended the existence of innate principles and a priori truths expressed as logical and mathematical truths. Their work emphasized deductive reasoning from self-evident principles to broad domains of knowledge.

Rationalism often stresses the role of mathematics, logic, and metaphysics as models of reliable, a priori knowledge. It has faced criticism from empiricists, notably David Hume, who questioned the justification of causality and the status of innate ideas. Immanuel Kant later proposed a synthesis, arguing that both reason and experience contribute to knowledge, notably through synthetic a priori judgments. Today, rationalist themes persist in discussions of epistemology, mathematics, and the philosophy of mind.