[From Latin rationalis: having the power of reasoning.]
(epistemology) Specifically, a tradition of philosophy in the 17th and 18th centuries that emphasized deductive reasoning and focused on the "hard" branches of philosophy (e.g., epistemology) instead of the value branches (e.g., ethics, politics, and aesthetics); the most prominent rationalists were Descartes (1596-1650), Leibniz (1646-1716), and Spinoza (1632-1677). More generally, any philosophy that is overly deductive and attempts to mold reality to fit its theories rather than the other way around; in this sense Platonism is a form of rationalism.