A reformer and abolitionist, his words and popular quotations would later inspire speeches by Abraham Lincoln and Martin Luther King Jr. Parker was born in Lexington, Massachusetts,[1] the youngest child in a large farming family.

He responded to these tragedies by refusing to lapse into what he called "the valley of tears", focusing instead on other events and demands, and by affirming "the immortality of the soul", later a benchmark of his theology.

[6] Descriptions of Parker as a teenager recall him as "raw" and rough, emotional and poetic, sincere, "arch", "roguish", volatile, witty, and quick.

He was accepted but could not pay the tuition, so he lived and studied at home, continued to work on his father's farm, and joined his classmates only for exams.

[12] While at Watertown, Parker produced his first significant manuscript, The History of the Jews, which outlined his skepticism of biblical miracles and an otherwise liberal approach to the Bible.

[15] His journal and letters show that he was acquainted with many other languages, including Chaldee, Syriac, Arabic, Coptic and Ethiopic.

Parker had spent 1836 visiting pulpits in the Boston area, but for family reasons accepted a pastorate at West Roxbury, Massachusetts, in 1837.

"The principle of morality is obedience to the Law of con[science]," he wrote, while religion required more: that we "feel naturally, allegiance to a superior Being: dependence on him & accountability to him."

Morality involves right acting, while religion requires love of God and regular prayer, which Parker considered essential to human life.

"[26] For years he had wrestled with the factuality of the Hebrew Scriptures, and by 1837 he was wishing "some wise man would now write a book…and show up the absurdity of…the Old Testament miracles, prophecies, dreams, miraculous births, etc.'"

"[27] Questions regarding biblical realism and meaning, and the answers clergy increasingly found through the German-based higher criticism, formed the basis of liberal Christianity as it emerged and developed throughout the nineteenth century.

In 1838 Parker published his first major article, a critical review of an orthodox work written by his former professor John Gorham Palfrey.

He instead argued for a type of Christian belief and worship in which the essence of Jesus's teachings remained permanent but the words, traditions, and other forms of their conveyance did not.

After this unwilling break with the Unitarian establishment, he spent two years (1841–1843) adjusting to the reality of his newly controversial and independent career and increasing his social activism on religious grounds.

[39] Returning to the United States, Parker found Unitarianism on the cusp of a division over his right to fellowship as a minister.

The debate over the nature and degree of Parker's "infidelity" caused Unitarians to adopt a liberal creed, which they had formerly declined to do based on an inclusive principle.

[41] Despite misgivings, Parker accepted and preached his first sermon at the Melodeon (Boston, Massachusetts) Theater in February.

[43] Parker's congregation grew to 2,000 and included influential figures such as Louisa May Alcott, William Lloyd Garrison, Julia Ward Howe (a personal friend), and Elizabeth Cady Stanton.

[44] Stanton called his sermons "soul-satisfying" when beginning her career, and she credited him with introducing her to the idea of a Heavenly Mother in the Trinity.

In Boston, he led the movement to combat the stricter Fugitive Slave Act, a controversial part of the Compromise of 1850.

Parker called the law "a hateful statute of kidnappers" and helped organize open resistance to it.

He and his followers formed the Boston Vigilance Committee, which refused to assist with the recovery of fugitive slaves and helped hide them.

Due to such efforts, from 1850 to the onset of the American Civil War in 1861, only twice were slaves captured in Boston and transported back to the South.

[47] As Parker's early biographer John White Chadwick wrote, Parker was involved with almost all of the reform movements of the time: "peace, temperance, education, the condition of women, penal legislation, prison discipline, the moral and mental destitution of the rich, the physical destitution of the poor" though none became "a dominant factor in his experience" with the exception of his antislavery views.

[48] He "denounced the Mexican War and called on his fellow Bostonians in 1847 'to protest against this most infamous war,'"[49] while at the same time promoting economic expansionism and exposing a racist view of Mexicans' inherent inferiority, calling them "a wretched people; wretched in their origin, history, and character".

He sought refuge in Florence because of his friendship with Elizabeth Barrett and Robert Browning, Isa Blagden and Frances Power Cobbe, but died scarcely a month following his arrival.

I do not pretend to understand the moral universe; the arc is a long one, my eye reaches but little ways; I cannot calculate the curve and complete the figure by the experience of sight; I can divine it by conscience.