Although outwardly an Episcopalian (even attending on a regular basis when Christ Church opened in Charlottesville in 1819 or 1820 until his death in 1826), Jefferson had privately embraced many key Unitarian views.
The following observations are not found in our book, Doubting Thomas, but I bring them up to make the point that people like Jefferson and others who were adopting the Unitarian-type theology, thought of themselves as the true Christians…as opposed to the Trinitarian Christians. In any event, when we use the word “Unitarian” today, it is very different than the word Unitarian in Jefferson’s day.
In short, the Unitarianism of Jefferson’s day is not the same as the Unitarianism of today. Initially, the Unitarians essentially did not disparage the Bible, like today’s Unitarians do (for the most part). For example, the foremost leader of the Unitarians at the outset of nineteenth century America was Rev. William Ellery Channing, pastor of the Federal Street Church of Boston. Listen to what Channing says about Unitarian beliefs (at the time): “We regard the Scriptures as the records of God’s successive revelations to mankind, and particularly of the last and most perfect revelation of His will by Jesus Christ. Whatever doctrines seem to us to be clearly taught in the Scriptures, we receive without reservation or exceptions.” This is found in his message called “An Attack on Orthodox Calvinism,” reproduced in Volume 4 of The Annals of America.
He went on to say, “We object to the doctrine of the Trinity that, while acknowledging in words, it subverts in effect, the unity of God. According to this doctrine, there are three infinite and equal persons possessing supreme divinity, called the Father, Son, and Holy Ghost.”
He called Trinitarian belief “irrational”: “We do, then, with all earnestness, though without reproaching our brethren, protest against the irrational and unscriptural doctrine of the Trinity.”
However, he does not reject the atonement of Christ. He refers to “the sufferings which [Jesus] bore for our salvation.” He adds, “We are particularly touched by His death, which was endured for our redemption. . . .”
Later, after Jefferson’s death, Unitarians became far more theologically liberal than we see in Channing’s comments above. But we must not make the anachronistic mistake of assuming that the Unitarians of Jefferson’s day were like today’s Unitarians, who for the most part reject the doctrines of the Bible. Unitarians in Jefferson’s day thought of themselves as Christians. A recent survey found that only 20% of Unitarians today consider themselves Christian.
 William Ellery Channing, “An Attack on Orthodox Calvinism,” The Annals of America, 20 vols., (Chicago, et al.: Encyclopaedia Britannica, 1976), 4:545.
 Ibid., 4:546.
 Ibid., 4:547.
 Ibid., 4:549.