A Defence of Poetry and Other Essays by Percy Bysshe Shelley

According to Wikipedia: "A Defence of Poetry is an essay by the English poet Percy Bysshe Shelley, written in 1821 and first published posthumously in 1840 in Essays, Letters from Abroad, Translations and Fragments (1840) [1839]. It contains Shelley's famous claim that "poets are the unacknowledged legislators of the world".