In philosophy, idealism is the group of philosophies which
assert that reality, or reality as we can know it, is fundamentally mental,
mentally constructed, or otherwise immaterial. Epistemologically, idealism
manifests as skepticism about the possibility of knowing any mind-independent
thing.
In a sociological sense, idealism emphasizes how human ideas —
especially beliefs and values — shape society. As an ontological doctrine,
idealism goes further, asserting that all entities are composed of mind or
spirit. Idealism thus rejects physicalist and dualist theories that fail to
ascribe priority to the mind. The corresponding idea in metaphysics is monism.
The earliest extant arguments that the world of experience is
grounded in the mental derive from India and Greece. The Hindu idealists in
India and the Greek Neoplatonists gave pantheistic arguments for an
all-pervading consciousness as the ground or true nature of reality. In
contrast, the Yogācāra School, which arose within Mahayana Buddhism in India in
the 4th century CE, based its "mind-only" idealism to a greater
extent on phenomenological analyses of personal experience. This turn toward
the subjective anticipated empiricists such as George Berkeley, who revived
idealism in 18th-century Europe by employing skeptical arguments against
materialism.
