Schopenhauer extended Kant's distinction between appearance and the thing-in-itself by arguing that the thing-in-itself is Will—a single, blind, purposeless striving that underlies all appearance, including the human body and its desires. In "The World as Will and Representation" (1818), he drew the pessimistic conclusion that because willing is endless and unsatisfiable, existence is structurally suffering, escapable only through aesthetic contemplation, compassion, or ascetic denial of the will.
Intellectual setting
Schopenhauer developed his system in explicit opposition to the post-Kantian idealism of Fichte and Hegel that dominated German universities in the 1810s-1820s, and drew on early translations of the Upanishads and Buddhist texts then becoming available in Europe; his ideas gained wide influence only in the 1850s-60s, late in his life.
Key ideas
The world as Will
Beneath the world of representation—objects structured by space, time, and causality—Schopenhauer posited a single underlying reality, Will, a blind and endless striving without ultimate purpose that manifests in gravity, instinct, and human desire alike.
Aesthetic contemplation and denial of the will
Because willing produces endless, unsatisfiable striving, Schopenhauer held that suffering is built into existence; temporary relief comes through will-less aesthetic contemplation (especially of music), and more lasting relief through compassion and ascetic renunciation of desire.
Legacy
Schopenhauer's account of the will and of suffering shaped Nietzsche's early thought, Wagner's operas, and Freud's theory of unconscious drives, and his engagement with Indian philosophy made him a key conduit between Buddhist and Vedantic ideas and nineteenth-century European thought.