idéalisme

The philosophical term was coined in the early eighteenth century, derived from Greek idea (form, pattern, from idein, to see). Leibniz used idéalisme in French around 1702 to describe positions like Berkeley's — that material objects exist only as perceptions. The word was clinical, not complimentary. It named a specific metaphysical thesis: reality is fundamentally mental.

German Idealism became the dominant philosophical movement of the late eighteenth and early nineteenth centuries. Kant's transcendental idealism held that space and time are not features of things-in-themselves but structures imposed by the mind. Johann Gottlieb Fichte, Friedrich Schelling, and Georg Wilhelm Friedrich Hegel each built systems of absolute idealism — reality as the self-development of mind, spirit, or the Absolute. Hegel's Phenomenology of Spirit (1807) was the summit of the tradition.

The popular meaning — idealism as optimism, as holding to high ideals — emerged in the nineteenth century and gradually displaced the philosophical meaning in common speech. An idealist in everyday English is someone who believes the world can be better. An idealist in philosophy is someone who believes the world is made of mind. The two meanings coexist without acknowledgment, causing confusion in every introductory philosophy class ever taught.

Marx and Engels attacked Hegelian idealism with dialectical materialism — turning Hegel 'on his head' by arguing that material conditions, not ideas, drive history. The idealism-materialism debate in philosophy mirrors the everyday opposition between dreamers and realists, but the technical meanings are stranger. Philosophical idealism is not dreaming. It is a serious claim about what exists.