What are the main points of Shelley's essay A Defence of Poetry?

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".