There was nothing in Abner Kneeland's upbringing to suggest that he would lead a highly unconventional life. He was born to a carpenter and his wife in 1774. He attended local schools in Worcester County and spent one term at a private academy in New Hampshire. At 21, Kneeland moved to Dummerston, Vermont, with his older brother to set up a carpentry business. Two years later, he married and joined a Baptist church in a nearby town. In 1801 Abner Kneeland began to preach the gospel.

But Kneeland's theology was constantly changing. After reading the works of Universalist Elhanan Winchester, he left the Baptist church and became a Universalist. In 1803 he met Hosea Ballou, one of Universalism's most influential and liberal thinkers. Ballou believed there was no need for human atonement, since finite creatures such as humans were incapable of offending an infinite God. Kneeland became a disciple of Ballou, who remained a lifelong friend, and began a career as a Universalist preacher.

For the next 26 years, as he served Universalist churches in New Hampshire, Vermont, Pennsylvania, New York, and Massachusetts, his theological views were moving farther and farther from Universalist teachings. At one point, he had such doubts about revealed religion and the authority of Scripture that he resigned his Boston pulpit and opened a dry goods store. An exchange of letters with Hosea Ballou convinced Kneeland to return to his pulpit.

As Kneeland continued to read and think, his certainty about divine revelation disappeared. He began to alienate and offend parishioners by asserting his own highly unorthodox interpretation of Universalist doctrine. He published feverishly, debated publicly, and created controversy wherever he went.

In 1824 he met the utopian socialist Robert Owen, who became his new mentor. The religious content of Kneeland's sermons was increasingly liberal and skeptical, and he began to call for social reform as well. He edited the Olive Branch and Christian Enquirer, a newspaper devoted to "free inquiry, pure morality, and rational Christianity." He lent his pulpit to Frances Wright, whose views on woman's rights, sexual freedom, dress reform, abolition, and other radical causes were considered scandalous. Kneeland himself publicly advocated for such unpopular reforms as equal rights for women and blacks, interracial marriage, birth control, divorce, and the right of married women to keep their own names and property.

Kneeland's theological liberalism and freethinking social views were too much for his Universalistic parishioners. It came as no surprise when in 1828 he was voluntarily "disfellowed" by the New England Universalistic General Convention.

Disfellowed but not disheartened, Kneeland moved to Boston in 1831 to become the lecturer for a newly formed "First Society of Free Enquirers." Each Sunday morning and Wednesday evening, he delivered radical social and ethical exhortations in the Federal Street Theater to crowds that regularly numbered over 2,000 people. He formed friendships with like-minded men, including William Ellery Channing, Ralph Waldo Emerson, Theodore Parker, and William Lloyd Garrison. Kneeland's newspaper, the Boston Investigator, promoted his radical social views and ultra liberal religious teachings and earned him the animosity of Boston's orthodox clergy and conservative authorities.

In December of 1833, the Investigator carried a letter Kneeland had written declaring that he did not believe in the Universalist conception of God. Although he denied being an atheist ("God and Nature are the same, hence I am not an atheist, I am a pantheist"), he was charged with blasphemy. Under Massachusetts law — then and now — blasphemy is defined as a libel of God. Questioning the existence of God was considered a blasphemous libel.

Kneeland defended himself by asserting his constitutional right to religious freedom and freedom of the press. The courts rejected his arguments; after numerous unsuccessful appeals, he was sentenced to 60 days in jail. His friends petitioned for his release, but more people signed a petition urging his imprisonment. Kneeland served his full sentence.

His time in jail seems to have extinguished his desire to quarrel with the New England establishment. He moved to Iowa and started a utopian community. It disbanded at his death in 1844.