<P> "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 by Edward Moxon in London . It contains Shelley's famous claim that "poets are the unacknowledged legislators of the world". </P> <P> The essay was written in response to his friend Thomas Love Peacock's article "The Four Ages of Poetry", which had been published in 1820 . Shelley wrote to the publishers Charles and James Ollier (who were also his own publishers): </P>

To which book is shelley responding in his defence of poetry