ἐνθουσιασμός

Enthusiasm comes from Greek ἐνθουσιασμός (enthousiasmós), from ἔνθεος (entheos), meaning 'having a god within,' from ἐν (en, 'in') and θεός (theos, 'god'). To be enthusiastic was, in the original Greek sense, to be filled with divine presence — possessed, overtaken, speaking with a voice not entirely one's own. The word described the state of the Delphic priestess inhaling volcanic vapors and prophesying, the Bacchic worshipper lost in ecstatic dance, the poet seized by the Muse. Enthusiasm was not an emotion. It was an invasion.

Plato treated enthusiasm with philosophical seriousness. In the Phaedrus, he distinguished four forms of divine madness: prophetic (from Apollo), ritual (from Dionysus), poetic (from the Muses), and erotic (from Aphrodite). Each was a form of enthousiasmós — a god entering the human vessel and temporarily displacing reason. Plato considered this divine madness superior to mere human sanity: the greatest blessings, he argued, come through madness, provided the madness is given by the gods. The philosopher who distrusted democracy and banished poets from his ideal republic nevertheless granted enthusiasm a place above reason.

The word's reputation collapsed in seventeenth-century England. During the English Civil War and its aftermath, 'enthusiasm' became a term of abuse applied to radical Protestant sects — Quakers, Ranters, Levellers — who claimed direct divine inspiration. John Locke, in his Essay Concerning Human Understanding (1689), devoted an entire chapter to enthusiasm, defining it as 'founded neither on reason nor divine revelation, but rising from the conceits of a warmed or overweening brain.' The word became synonymous with dangerous fanaticism, irrational fervor, and the refusal to submit private revelation to public reason.

The rehabilitation of enthusiasm took another century. By the late eighteenth century, Romantic writers had reclaimed the word. Shaftesbury, Diderot, and the German Romantics argued that enthusiasm — passionate engagement, creative fire, moral conviction — was not madness but the highest form of human experience. The word gradually softened from 'possessed by a god' to 'very interested in something.' The god departed; the warmth remained. Modern enthusiasm for a hobby, a sports team, or a new restaurant carries no trace of the Delphic oracle or the Puritan fanatic — only a faint, domesticated glow where divine fire once burned.