Raised in a pious evangelical Baptist family, Potter was a precocious boy who by the age of three was able to recite entire Bible passages from memory. Potter accepted a Baptist pastorate in Dover, New Hampshire, in 1908 and another in Mattapan, Massachusetts, in 1910. During Potter’s years as a Baptist preacher he began to question many of the orthodox Christian tenets with which he had been raised. He was increasingly influenced by liberal theological ideas, especially the “higher criticism” of the Bible. In 1914 frustration with Baptist church leaders who questioned his theological views led to his resignation from the Baptist ministry and conversion to Unitarianism.
In 1919 Potter was called to be minister of the West Side Unitarian Church in New York City, where he served from 1920-25. Under Potter’s stimulating leadership the West Side Unitarian Church became a focal point of liberal thought, activity and interpretation of the scriptures. Potter came to national attention in 1923-24 when he participated in a series of radio debates with the formidable fundamentalist Baptist pastor, Rev. John Roach Straton of the Calvary Baptist Church in Manhattan. The debates at Carnegie Hall stirred public interest in the fundamentalist-modernist doctrinal questions that were circulating at the time. They were soon published in four volumes entitled The Battle Over the Bible, Evolution versus Creation, The Virgin Birth—Fact or Fiction?, and Was Christ Both Man and God?