Dear SirYou go, Tommy!
-- The wishes expressed, in your last favor, that I may continue in life and health until I become a Calvinist, at least in his exclamation of `_mon Dieu!_ jusque a quand'! would make me immortal. I can never join Calvin in addressing _his god._ He was indeed an Atheist, which I can never be; or rather his religion was Daemonism. If ever man worshipped a false god, he did.
Whilst Thomas Jefferson did believe that the vast majority of thinkers of history believed in a Creator and he would accept that idea as a Deist, it's a mistake to use this letter as support for the claim that he would be in favor of Intelligent Design based on what we know today. The man was very intelligent and would have updated his views based on what has been learned since his life, and would therefore, by the reasoning used in this letter, eschew ID today.
If Jefferson was a Deist why did he pray to God? Per Deism, God is indifferent to the world, so it would make no sense whatsoever for a Deist to pray.