Substance: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Photos

Marble bust of Aristotle with a beard and draped robe, showing detailed facial features and wavy hair, set against a dark background.

Portrait of Benedict de Spinoza, 17th-century Dutch-Jewish philosopher, with shoulder-length dark hair, white collar, and black robe, set against a dark background.

See All Images →

Topics

philosophy Identity Truth existence of God Form Postmaterialism Logos A priori knowledge Free will Best of all possible worlds Reductionism

Dig Deeper: More Articles That Discuss This Topic