Philosophical History of Idealism

The philosophical history of Idealism—the view that reality is fundamentally mental, spiritual, or immaterial—can be traced to ancient traditions in both Eastern and Western thought and to more recent explorations by German, British, and American philosophers in the 18th to 20th centuries.

Eastern and Classical Roots of Idealism

In Eastern philosophy, the Upanishads (c. 800–300 BCE, India) taught that Brahman (ultimate reality) is identical with Atman (self)—a startlingly original idealist insight that has consciousness as primitive and fundamental. The material world (Maya) is often seen as illusion, or at least derived from consciousness, which leads to a non-dual consciousness-only reality (see next sections). (The Upanishads are the final part of the Vedas, the most ancient and sacred scriptures of Hinduism, written in Sanskrit.)

In Western Philosophy, Plato (c. 428–348 BCE) is generally credited with laying the groundwork for Idealism with his theory of Forms. He argued that ultimate reality consists not of the material world, but of eternal, unchanging Forms or Ideas (e.g., the Form of Beauty, Justice, etc., and his Allegory of the Cave shows how the physical world is merely a shadow of the true reality of the Forms). These Forms are apprehended only by the mind, not by the senses. While not a robust Idealism of later philosophers, Plato's metaphysics stresses non-material worlds as being more real than the material world. The Neoplatonist Plotinus (c. 204–270 CE) developed a more spiritualized system, making the case for an immaterial source of all existence, called the One—a purely intellectual and spiritual reality from which all things emanate. Reality, then, descends from mind (Nous) to soul to matter, with matter being the least real.

Modern European Idealism

The philosopher most associated with idealism and primarily responsible for its modern development was the Anglo-Irish philosopher, writer, and clergyman George Berkeley (1685–1753). Known as Bishop Berkeley, he is the originator of what he called “immaterialism,” which was later labeled “subjective idealism” and is now known simply as “idealism.” The core idea is that physical objects do not exist outside a mind that perceives them; reality consists of minds (or spirits) and their ideas, with no matter existing independently of perception. His famous slogan is esse est percipi (aut percipere)—to be is to be perceived (or to perceive). The immediate objects of perception are ideas, which are passive; only spirits are active. The orderly, law-governed stability of the world reflects the coordinating will of God, the omnipresent perceiver who guarantees continuity of existence even when no human is doing the perceiving. In other words, for an object to exist, it must be perceived either by a human mind or, to account for objects not being observed by sentient beings, by the omnipresent mind of God.

Berkeley rejects the notion of abstract ideas and the supposed “substratum” of matter, insists that ideas can only resemble ideas (the “likeness principle”), and presents his famous “master argument”—that you cannot coherently conceive an unconceived object. He dismisses the idea of a mind-independent material substance, arguing that such a thing is impossible to conceive and unnecessary to explain our experience of the world. To Berkeley, this is not skepticism but common sense—tables and trees are nothing more than collections of ideas or sensations that exist only in our minds; they are simply stable bundles of ideas presented to us according to divine laws.

German Idealism began with Immanuel Kant (1724–1804), who was influenced by Berkeley; his deservedly famous work, Critique of Pure Reason, initiated the modern Idealist movement by offering “transcendental idealism”—the view that we can only know phenomena (things as they appear), not noumena (things-in-themselves). Johann Gottlieb Fichte (1762–1814) developed subjective idealism, introducing a self-generating subjectivity by articulating the self's role in constructing knowledge; the “I” posits both itself and the “not-I” (external world). Friedrich Wilhelm Joseph Schelling (1775–1854) sought to unify nature and spirit, theorizing that nature is a visible spirit and spirit is an invisible nature. Georg Wilhelm Friedrich Hegel (1770–1831) had enormous influence; his Phenomenology of Spirit developed absolute idealism, in which reality unfolds through a dialectical process of thesis, antithesis, and synthesis. Arthur Schopenhauer (1788-1860), in his The World as Will and Representation, has the Will as the inner essence of all things; our individual consciousness is a localized reflection of the universal Will.

British and American Idealism

British Idealism arose in the mid-to-late 19th century, inspired by German Idealism, especially Hegel. Its peak was arguably Francis Herbert Bradley (1846–1924), whose Appearance and Reality argues that empirical reality is contradictory and must be transcended by the Absolute, an all-encompassing whole. J. M. E. McTaggart (1866–1925) posited that time is not real (his A-series and B-series distinction) and developed a metaphysical form of personal idealism.

American Idealism (also called Objective Idealism) was shaped by German Idealism, especially Transcendentalism. Ralph Waldo Emerson (1803–1882), a literary giant (not a systematic philosopher), created the Transcendentalist movement, emphasizing the soul, intuition, and nature as manifestations of the divine. Charles Sanders Peirce (1839–1914), while primarily a pragmatist, espoused a form of objective idealism—reality as governed by intelligible laws or signs.