The tradition represented by the great 17th-c figures Descartes, Leibniz, and Spinoza, who believed that the general nature of the world could be established by reason alone, through a priori knowledge independent of sense-experience. It is usually contrasted with empiricism. In a popular sense, a commitment to reason as opposed to faith, convention, or emotion. It is therefore contrasted with irrationalism.
In philosophy and in its broadest sense, rationalism is "any view appealing to reason as a source of knowledge or justification" (Lacey, 286). 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).
In various contexts, the appeal to reason is contrasted with revelation, as in religion, or with emotion and feeling, as in ethics.
Within the Western philosophical tradition, "rationalism begins with the Eleatics, Pythagoreans, and Plato, whose theory of the self-sufficiency of reason became the leitmotif of Neoplatonism and idealism" (Runes, 263). Since the Enlightenment, rationalism is usually associated with the introduction of mathematical methods into philosophy, as in Descartes, Leibniz, and Spinoza (Bourke, 263).
Rationalism is often contrasted with this view known as empiricism. 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.
Philosophical usage
The distinction between rationalists and empiricists was drawn at a later period, and would not have been recognised by the philosophers involved. for example, the three main rationalists were all committed to the importance of empirical science, and in many respects the empiricists were closer to Descartes in their methods and metaphysical theories than were Spinoza and Leibniz.
History of rationalism
Classical Greek rationalists
Socrates (ca 470–399)
Socrates firmly believed that, before anyone can understand the world, they first need to understand themselves.
Neoplatonism
René Descartes (1596–1650)
Descartes thought that only knowledge of eternal truths – including the truths of mathematics, and the epistemological and metaphysical foundations of the sciences – could be attained by reason alone; He also argued that although dreams appear as real as sense experience, these dreams cannot provide persons with knowledge. Descartes developed a method to attain truths according to which nothing which cannot be recognised by the intellect (or reason) can be classified as knowledge.
Descartes therefore argued, as a result of his method, that reason alone determined knowledge, and that this could be done independently of the senses.
Baruch Spinoza (1632–1677)
Baruch Spinoza, a key precursor to the Age of Enlightenment, offered both a solution to the mind-body problem and determined the relationship between God as an infinite substance with the finite substance of the world. As a corollary of this, God is the only being that exists, of necessity, and the empirical world is just modifications of the infinite attributes of God, of which we are aware by thought and reason.
In opposition to Descartes, Spinoza argued that there is only one substance, and that this is God when conceived under the attribute of thought, natura naturans, and Nature when conceived under the attribute of extension, natura naturata.
Gottfried Leibniz (1646–1716)
Leibniz was the last of the great Rationalists, who contributed heavily to other fields such as mathematics. Leibniz rejected Cartesian dualism, and denied the existence of a material world. In Leibniz's view there are infinitely many simple substances, which he called "monads" (possibly taking the term from the work of Anne Conway).
Leibniz developed his theory of monads in response to both Descartes and Spinoza. Monads are the fundamental unit of reality, according to Leibniz, constituting both inanimate and animate things. Leibniz therefore introduced his principle of pre-established harmony, in order to account for apparent causality in the world.
Immanuel Kant (1724–1804)
Immanuel Kant started as a traditional rationalist, having studied the rationalists Leibniz and Wolff, but after studying David Hume's works which "awoke [him] from [his] dogmatic slumbers", he developed a distinctive and very influential rationalism of his own which attempted to synthesise the traditional rationalist and empiricist traditions. Leibniz, Gottfried (1714), Monadology. Kant, Immanuel, (1781/1787), Critique of Pure Reason.
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