<metaphysics, philosophical school> in metaphysics, idealism is a term used to describe the sort of theory which claims that something "ideal" or non-physical or non-material or non-extended is the primary reality. In this sense, Plato, Berkeley, Leibniz and Hegel are among the most significant of the idealists (Leibniz is perhaps the most consistent, since he said that all physical things are actually made up of little bundles of consciousness he called "monads", an idea that is close to panpsychism). Obviously, spiritualism is similar to idealism, but spiritualism tends to be used to refer more to religious, supernatural conceptions of reality, rather than to philosophical theories like those of Plato or Hegel. Plato can be considered the "Founding Father" of idealism in Western philosophy, since he claimed that what is fundamentally real are ideas, of which physical objects are pale imitations. The opposite of idealism is materialism. Just as materialism in metaphysics is often linked with subjectivism in epistemology, idealism is often linked with intrinsicism in epistemology (though epistemological intrinsicism is sometimes also called, confusingly, idealism, since intrinsicism holds that we literally perceive universals or ideas). In popular usage, "idealism" is more of an ethical term, characterizing people who have a strong code of values or a great deal of integrity, though sometimes to an excessive degree (often contrasted with those who are merely or healthily pragmatic). (References from absolutism, abstractionism, Cartesianism, dualism, essentialism, Hegelianism, intrinsicism, Kantianism, Marxism, materialism, mentalism, monism, Neo-Platonism, Platonism, realism, spiritualism, and transcendentalism.)
[The Ism Book]
<history of philosophy, gnoseology, metaphysics> belief that only mental entities are real, so that physical things exist only in the sense that they are perceived. Berkeley defended his "immaterialism" on purely empiricist grounds, while Kant and Fichte arrived at theirs by transcendental arguments. German, English, and (to a lesser degree) American philosophy during the nineteenth century was dominated by the monistic absolute idealism of Hegel, Bradley, and Royce. Recommended Reading: David Berman, George Berkeley: Idealism and the Man (Oxford, 1996); German Idealist Philosophy, ed. by Rudiger Bubner (Penguin, 1997); The Cambridge Companion to German Idealism, ed. by Karl Ameriks (Cambridge, 2001); John Foster, The Case for Idealism (Routledge, 1982); and Current Issues in Idealism, ed. by Paul Coates and Daniel D. Hutto (St. Augustine, 1997).
[A Dictionary of Philosophical Terms and Names]
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