Jefferson’s approach to moral values differed in the details but was similar at the bottom line. Jefferson’s starting point was what historian Gregg Frazer labels theistic rationalism. Frazer means that Jefferson was willing to concede the existence of God on logical grounds, but reason was always in the driver’s seat when it came to determining his religious beliefs. He rejected as irrational almost all of the fundamental tenets of orthodox Christianity (as outlined in the Apostles’ Creed, for example), was skeptical of the concept of special revelation, and insisted repeatedly that reason was the only reliable guide to virtue.And the second:
... If we were to imagine a continuum of religious belief, theistic rationalism would fall somewhere between orthodox Christianity (defined by historic confessions such as the Apostles’ or Nicene creeds) and Deism.
The latter is a slippery concept. Deism in the late-eighteenth century was not embodied in a formal denomination. It had no official creed or confession, and I’ve come across a range of definitions of it in my reading. I can’t say that Frazer’s understanding of Deism is the right one, but I do applaud him for offering a precise definition up front. Deism, as Frazer defines it, has two distinguishing characteristics: The first is the belief in an absent God, a Deity who takes no active role in his creation. There is no logical reason to pray to such a God or to expect this watchmaker Creator to intervene in human affairs. The second distinguishing feature, which follows logically from the first, is the rejection of the very possibility of what theologians call “special” (as opposed to “general”) revelation. The God of Deism does not speak to humankind except through the order inherent in the natural world.