Rationalist

A rationalist is a person who holds that reason is the primary source of knowledge and justification, often independent of sensory experience. In epistemology, rationalism is the view that significant propositions about the world can be known through reason alone or via deduction from self-evident principles, sometimes with the aid of innate ideas.

In Western philosophy, early modern rationalists include René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz, who argued that mathematics, logic, and basic metaphysical truths can be established a priori. Earlier and contemporary Islamic and Jewish philosophers, such as al-Farabi, Avicenna, and Maimonides, also developed rationalist methodologies, integrating logic with revelation or tradition.

In ordinary use, a rationalist describes someone who emphasizes reason and evidence in forming beliefs, often contrasting with empiricists who stress sensory experience. The term can indicate a stance within secular humanism or scientific skepticism, but it also designates a broad temperament toward thorough, coherent thinking rather than a single, cohesive movement.

The rationalist program faces critiques that rational deduction may mislead without empirical input, and debates over innate ideas or the meaning of a priori knowledge. Immanuel Kant argued that pure rationalism cannot by itself yield knowledge of the empirical world, prompting a synthesis of reason and experience in subsequent philosophy.