Idealism

What it is

Idealism holds that mind or consciousness is fundamental, and that the physical world is derivative — constituted by experience rather than existing independently of all experience.

It is not the claim that the world is imaginary, and it is not the claim that wishing changes things. An idealist expects the tram to hit you if you step in front of it. The disagreement with physicalism is about what the tram most fundamentally is, not about whether it will hurt.

The label covers positions that differ enormously:

• Subjective idealism (Berkeley) — to exist is to be perceived; objects are collections of ideas, held in being by God's continuous perception when nobody else is looking
• Transcendental idealism (Kant) — we can only know the world as it appears through the structures of our own minds, and things as they are in themselves remain permanently out of reach. This is a claim about the limits of knowledge, and Kant was emphatic that it is not Berkeley's position
• Absolute idealism (Hegel, Bradley) — reality is a single rational whole, and mind is its fundamental character

Kant and Berkeley are routinely lumped together and should not be. Kant spent considerable energy insisting on the difference.

Where it came from

Berkeley published the Principles of Human Knowledge in 1710, arguing that the notion of matter existing unperceived is not merely false but incoherent — we cannot so much as form the idea. Esse est percipi: to be is to be perceived. His argument is far harder to refute than its reputation suggests, and Samuel Johnson's famous rebuttal of kicking a stone missed the point entirely, since Berkeley never denied that stones resist feet.

Kant's Critique of Pure Reason (1781) reframed the whole question. German idealism ran on through Fichte, Schelling and Hegel; British idealism dominated English-language philosophy until the early twentieth century, when Russell and Moore turned decisively against it.

Comparable positions developed independently elsewhere, and the comparison should be made carefully rather than eagerly. Advaita Vedanta holds that Brahman alone is ultimately real and the world of separate things is māyā; Yogācāra Buddhism is often translated as "mind-only". Both get called idealism in popular writing. Specialists in both traditions dispute the label, on the grounds that these schools are answering soteriological questions about liberation rather than metaphysical questions about what exists, and that the categories do not map cleanly. Treat the resemblance as a starting point for reading, not as an established identity.

How it is used

Academically it survives as a minority position with a recent modest revival — the contemporary analytic version associated with Bernardo Kastrup has drawn attention, along with sustained criticism, and should be read as a live proposal under argument rather than a settled result.

In the spiritual world, idealism is invoked constantly. "Consciousness creates reality" is close to a slogan, and it is usually offered as though Berkeley, Kant, quantum mechanics and the Upanishads had jointly established it.

This is where an honest article has to be blunt. The popular claim does not follow from the philosophical position. Berkeley's world is stable, law-governed and emphatically not subject to your preferences — its constancy comes from God's perception, not yours. Kant's categories are universal structures of any possible mind, not personal ones you can adjust. Neither philosopher offers the slightest support for the idea that a person can alter their circumstances by changing their thoughts about them.

Idealism says mind is fundamental to reality. It does not say your mind is in charge of it. The slide between those two is where a difficult metaphysical thesis becomes a marketable one, and it is worth watching for, because a great deal is sold on the strength of it.

What we can and cannot say

We can say idealism is a coherent and serious position that has never been refuted, held by some of the most careful thinkers in the tradition, and that its central complaint against physicalism has force: we only ever encounter the world through experience, so treating experience as the derivative thing does invert the order in which we actually meet reality.

We can say it has one clear advantage — the hard problem of consciousness does not arise, because it does not have to derive mind from something mindless.

We can say it pays for that with its own problems, and the sharpest is regularity. If the world is fundamentally mental, why is it so consistent, so shared, so indifferent to what we want, and so full of detail nobody has ever observed? Berkeley needed God to hold it steady. Later idealists need something to do that work, and what they use is generally the least convincing part of the system.

We cannot say the matter is settled either way, and we should say clearly that no experiment currently distinguishes idealism from physicalism, because both predict the same observations. Anyone claiming that quantum mechanics has proved idealism is going well beyond what physicists — including those sympathetic to the idea — will endorse.

Further reading

• George Berkeley, A Treatise Concerning the Principles of Human Knowledge (1710) — short, and much stronger than its caricature.
• Immanuel Kant, Critique of Pure Reason (1781) — difficult; the Prolegomena is the usual way in.
• Paul Guyer and Rolf-Peter Horstmann, "Idealism", Stanford Encyclopedia of Philosophy — free, and good on the distinctions the popular usage collapses.