In
epistemology and in its modern sense,
rationalism is "any view appealing to
reason as a source of knowledge or justification" (Lacey 286). In more technical terms it is a method or a
theory "in which the criterion of the truth is not sensory but intellectual and
deductive" (Bourke 263). Different degrees of emphasis on this method or theory lead to a range of rationalist standpoints, from the moderate position "that reason has precedence over other ways of acquiring knowledge" to the radical position that reason is "the unique path to knowledge" (Audi 771). Given a pre-modern understanding of reason, "rationalism" is identical to
philosophy, the Socratic life of inquiry, or the zetetic interpretation of authority (open to the underlying or essential cause of things as they appear to our sense of certainty). In recent decades,
Leo Strauss sought to revive
Classical Political Rationalism as a discipline that understands the task of reasoning, not as foundational, but as
maieutic.
Since the Enlightenment, rationalism is usually associated with the introduction of mathematical methods into philosophy, as in Descartes, Leibniz, and Spinoza (Bourke 263). This is commonly called continental rationalism, because it was predominant in the continental schools of Europe, whereas in Britain empiricism dominated.
Rationalism is often contrasted with empiricism. Taken very broadly these views are not mutually exclusive, since a philosopher can be both rationalist and empiricist (Lacey 286–287). Taken to extremes the empiricist view holds that all ideas come to us through experience, either through the five external senses or through such inner sensations as pain and pleasure, and thus that knowledge is essentially based on or derived from experience. At issue is the fundamental source of human knowledge, and the proper techniques for verifying what we think we know (see Epistemology).
Proponents of some varieties of rationalism argue that, starting with foundational basic principles, like the axioms of geometry, one could deductively derive the rest of all possible knowledge. The philosophers who held this view most clearly were Baruch Spinoza and Gottfried Leibniz, whose attempts to grapple with the epistemological and metaphysical problems raised by Descartes led to a development of the fundamental approach of rationalism. Both Spinoza and Leibniz asserted that, in principle, all knowledge, including scientific knowledge, could be gained through the use of reason alone, though they both observed that this was not possible in practice for human beings except in specific areas such as mathematics. On the other hand, Leibniz admitted that "we are all mere Empirics in three fourths of our actions" (Monadology § 28, cited in Audi 772). Rationalism is predicting and explaining behavior based on logics.
