Idealism

Idealism is the family of metaphysical positions holding that reality is fundamentally mental in nature — that what we call the physical world either depends on, is constituted by, or is identical with mind, experience, or idea. Against the common-sense view that the material world exists independently of any observer, idealism maintains that matter is ontologically secondary or derivative.

The tradition runs from Plato's doctrine of Forms (the most real things are the eternal objects of intellect, not the passing phenomena of sense) through George Berkeley's esse est percipi (to be is to be perceived) to German Idealism's claim — in Fichte, Schelling, and most systematically in Hegel — that the whole of reality is the self-development of Spirit (Geist). Each version draws the boundary between mind and world differently, but all share the commitment that the mind-independent world, if it exists at all, is not what is ultimately real.

Idealism was the dominant tradition in European philosophy through most of the nineteenth century, and its collapse under the combined pressure of scientific naturalism, Logical Positivism, and the analytic tradition's revolt against idealism around 1900 was one of the most rapid and decisive philosophical reversals on record. That collapse has not been fully reckoned with: many of idealism's questions — about the relationship between consciousness and physical reality, about the grounding of objective knowledge in subjective experience — are now posed in the vocabulary of Philosophy of Mind without acknowledgment of their idealist provenance. The questions survived the tradition that originally formulated them.