Thomas Jefferson apparently is one of the most contradictory persons in this context: one of the largest slave holder in the country, yet, denied the right to import slaves to United States, yet, did nothing to discourage the local slave trades, yet, did plan on gradual liberation of slaves, yet, held Africans to be inferior to Europeans – a list of paradoxes that just keeps growing. This is an interesting muddle to deal with, but one which I regretfully will have to leave for specialists of Jefferson's thought.
I am now mostly interested in Jefferson's religious ideas, or more precisely, in the way how he suggested religion should be seen in the affairs of state. Of course, his religious ideas as such are also of interest. Apparently, he had constructed his very own version of Gospels, cutting up pieces of life story and sayings of Jesus from all the Gospels and putting it all together into a whole. Particularly, Jefferson had discarded all descriptions of miracles and all suggestions of the divinity of Jesus, which might suggest that he was a deist of some sort.
Although Jefferson thus disparaged all ideas of supernatural, he appears to still have been interested of Christianity – why else would he go through the trouble of picking up lines from Bible? The idea of Jesus as a mere teacher of morality was, of course, a standard line in Enlightenment. Yet, it is of interest what Jefferson appropriated from these moral teachings.
The famous Virginia Statue of Religious Freedom (1777) begins with a statement that God created human beings free (well, technically Jefferson is speaking only of ”man”, but I am giving him the benefit of doubt and assume he isn't really restricting his statement to one gender). This is a crucial assumption in many versions of Christianity – freedom is an essential precondition for human responsibility (of course, Augustine might be of a different opinion, but I doubt Jefferson really cared about Augustine in this matter).
When Jefferson speaks of God as an author of ”our religion”, that is, Christianity, it is difficult to say how serious he really is – even if Jefferson believed in God, his God probably was an author of no religion. Yet, this statement is obviously a rhetorical move – it gives an air of authority and responsibility for what Jefferson is about to say.
Jefferson's strategy is to take some of the central ingredients of Christianity (or what he sees as these central thoughts). Humans are created free, thus, we must respect their freedom in every matter. Especially this holds of religion. If God would have wanted, he could have made us follow Christiniaty by default – yet, we know by experience he hasn't. Thus, we must follow God's example in this case and let everyone decide their own religious opinions for themselves, especially as every human being is by default prone to fall in error and thus no one person's judgement on religious affairs should be followed.
Jefferson's idea concurs with modern sensibilities, and his argument is also quite beautiful, relying on central ideas of the supposed opposition. It is quite astonishing to think that two quite different influences were behind the American revolution – the freethinking deism of Jefferson and the belief in personal guidance of God by Benjamin Franklin. A more speculative thinker might even suggest that these two ideologies are still battling of the spirit of American people, perhaps in the guise of very party system of that country.