Rationalism: 1. The doctrine associated especially with the French philosopher Rene Descartes (1596-1650), the Dutch philosopher Baruch Spinoza (1632-77), and the German philosopher and mathematician Gottfried Wilhelm von. Liebniz (1646-1716) that it is possible to obtain knowledge by reason alone, that there is only one valid system of reasoning and it is deductive in character, and that everything is explicable in principle by this form of reasoning…. 2. The more general view that everything is explicable in principle by one system of reasoning. 3. A general commitment to reason as opposed to faith, religious belief, prejudice, tradition, or any other source of belief that is without foundation in reason. Rationalist: one who believes in or practices rationalism (1, 2, 3). Rationalistic.
Excerpted from: Colman, Andrew M., ed. Oxford Dictionary of Psychology. New York: Oxford University Press, 2003.