What is the purpose of poetry?

What is the purpose of poetry? Not that hard to figure out. Is it?

"When criticism becomes a pursuit separate from poetry, those who follow it are apt to forget that the legitimate ends of the art for which they lay down rules are instruction and delight, and these points being obtained by what road soever, entitled the poet to claim the prize of successful merit."

Walter Scott

Memoirs 
also 
The Dramatic Work of John Dryden


Scott was a literary heavyweight, much neglected these days.