Parker, Theodore (1810-60), was the son of a small farmer at Lexington, Massachusetts. While remaining a farmer he studied at Harvard. In 1837, after having for some years kept a school, he became a Unitarian minister, but in consequence of a sermon preached in 1841 lost many of his supporters, and had to retire to Europe. In 1846 he seceded, and joined a freer society. His later years were occupied in preaching and writing, the abolition of slavery finding in him ct powerful advocate. He died at Florence.