Stephen Symonds Foster (1809–1881) was a radical American abolitionist known for his dramatic and aggressive style of public speaking, and for his stance against those in the church who failed to fight slavery. His marriage to Abby Kelley Foster brought his energetic activism to bear on women's rights. He spoke out for temperance, and agitated against any government, including his own, that would condone slavery.

Foster helped establish the New Hampshire Anti-Slavery Society, and belonged to the 'New Hampshire radicals' group within the American Anti-Slavery Society. Foster wrote anti-slavery tracts and published in 1843 a widely-discussed book that met with protest and critical response: The Brotherhood of Thieves; or A True Picture of the American Church and Clergy: A Letter to Nathaniel Barney, of Nantucket. At Liberty Farm where they lived, Foster and his wife formed a link on the underground railroad, and helped fugitive slaves gain their freedom.

http://en.wikipedia.org/wiki/Stephen_Symonds_Foster