Randall Cluff, "Whittier, John Greenleaf," American National Biography Online, February 2000, http://www.anb.org/articles/16/16-01765.html.
Despondent over the headaches that interrupted his work and his lack of direction in life, Whittier reached a turning point in 1833. Garrison wrote asking him to join the fledgling abolitionist movement. Recognizing the risks—both northern and southern interests opposed abolitionism—he joined, believing such a course to be morally correct and socially necessary. In June 1833 he published the antislavery pamphlet Justice and Expediency and in December was a founding member of the American Anti-Slavery Society. He would later regard his signing of the Anti-Slavery Declaration of 1833 the most important thing he had done.