The essay presents the figure of the poet in romantic terms as a seer and a genius rather than simply a literary craftsman and an imitator of past classical models. According to Shelley, the poet can communicate universal truths about human existence and contribute to the progress of mankind. Poetry is the medium through which the poet can express his vision. A Defense of Poetry was intended as a polemical reply to Thomas Love Peacock's essay "The Four Ages of Poetry" (1820), where the author argued that poetry was not relevant in an advanced society. Shelley countered that poetry was vital and that poets made a definite contribution to improve society. Because of this, Shelley described poets as "the unacknowledged legislators of the world".