One of the surest tests [of a poet’s superiority or inferiority] is the way in which a poet borrows. Immature poets imitate; mature poets steal; bad poets deface what they take, and good poets make it into something better, or at least something different. The good poet welds his theft into a whole of feeling which is unique, utterly different than that from which it is torn; the bad poet throws it into something which has no cohesion. A good poet will usually borrow from authors remote in time, or alien in language, or diverse in interest.
There was an old man of Port Grigor,
Whose actions were noted for vigour;
He stood on his head
till his waistcoat turned red,
That eclectic old man of Port Grigor.
He was black in the face,
and they scarcely could trace
The least likeness to what he had been:
While so great was his fright
that his waistcoat turned white –
A wonderful thing to be seen!