Although he knew that joining the Abolitionist Movement would mean neglecting his poetry, Whittier felt it was his duty to fight this evil. In " Proem" he acknowledges the sacrifice he is making, but like John Milton and Andrew Marvell, seventeenth century British poets who used their gifts for the cause of religious freedom, Whittier feels it would be wrong not to devote his “gift” to fighting the evil of slavery.
This was a sacrifice not only because of the time lost from the creation of less polemical and dated poetry, but because the anti-slavery cause was as yet an unpopular one in New England, and his advocacy of the cause could cost him opportunities to get his work published.
O Freedom! If to me belong
Nor mighty Milton's gift divine,
Nor Marvell's wit and graceful song,
Still with a love as deep and strong
As theirs, I lay, like them, my best gifts on they shrine!
Full text of "Proem"