Idealism
idealist
The view that reality is fundamentally mental — that what exists is minds and their contents, and the physical world depends on being perceived or thought.
In practice
Any claim that the world as you encounter it is shaped by the apparatus you encounter it with is a descendant of this argument, whatever else you believe.
The common mistake
Confusing philosophical idealism with having ideals. The position is about what exists, not about optimism or high standards.
Idealism reverses the usual picture. Rather than mind emerging from matter, matter is a feature of, or dependent on, mind.
Berkeley's version
George Berkeley gave the sharpest form in 1710. Everything you know of an object is the ideas it produces in you. Positing matter behind those ideas adds an entity you can never encounter and which does no explanatory work. So to be is to be perceived — esse est percipi.
The obvious objection is that objects seem to persist unobserved. Berkeley's answer is that they are perceived by God, which keeps the world stable at the cost of a large commitment.
He is more resistant than he first appears. He is not denying that things are real or that the world is orderly; he denies that their reality consists in material substance, which was already a philosophical posit rather than something observed.
Kant's transcendental idealism
Kant's version is different and more influential. Appearances depend on the structures of our cognition — space, time and the categories are contributed by the mind — while things as they are in themselves remain beyond what we can know.
This is not Berkeley's claim. Kant insists appearances are empirically real; he denies only that they are reality independent of the conditions under which anything can be experienced. See transcendental idealism.
Absolute idealism
Hegel and the German idealists found Kant's unknowable thing-in-itself unstable and dropped it, treating reality as the development of spirit or absolute reason. The result dominated European philosophy for a century and was the target that analytic philosophy formed against — Russell and Moore broke with it in Cambridge around 1900.
Why it is still argued
Idealism is a minority position and it points at a real difficulty: physical description reaches everything except the perspective from which the describing happens. Panpsychism, which some philosophers of mind now treat as worth taking seriously, is a nearby response to the same pressure. See materialism.
Concept web
Open the full webQuestions
What is idealism in philosophy?
The view that reality is fundamentally mental — that what exists is minds and their contents, and the physical world depends on being perceived or thought rather than existing independently.
What does 'esse est percipi' mean?
To be is to be perceived. Berkeley's claim that an object's existence consists in being perceived, since everything known of it is the ideas it produces.
How is Kant's idealism different from Berkeley's?
Kant holds that appearances are empirically real and depend on the structures of cognition, while things in themselves are unknowable. Berkeley denies that anything exists behind perception at all.