John Adams was Unitarian. Benjamin Franklin was a Freethinker. James Madison drank.
"James Madison drank." I drink and don't think for a second that I don't believe in GOD!
Well, ya gotta believe in something. I believe I'll have a drink, too.
Also notice that Franklin thanks God for helping him to lead a good life. Franklin does not often show a religious side, and he will explain in greater depth later on that he is a Deist, or one who believes in a usually non-interventionist God without ascribing to any particular religious denomination. We are perhaps to believe that Franklin assumes either a false humility at the beginning of the book or that he grew in faith in his later years.
http://www.sparknotes.com/lit/franklinautobio/section1.html