This is from an address that Hamilton biographer Richard Brookhiser gave to the Family Research Council. That such conservative sources reinforce my interpretation of Hamilton's religion shows that among serious Hamilton scholars of whatever political persuasion this is not a matter of debate: He was not an orthodox Christian when he did his principle work founding America.
This part of his life is important because he goes through many phases. The people who knew him as a young man, namely a man named Robert Troup who went to King's College with him, remembered him being very devout--saying his prayers. Troup remembered saying prayers with Hamilton. One of the people who sent him to this country was a minister named Knox. So there were these influences operating on Hamilton early in his life.
It seems to me that when he got involved in the war, on Washington's staff, and in politics, he really put that aside. I don't see much emphasis of religion continuing to motivate him in this part of his career. He does ghost the farewell address and that has a famous paragraph about the importance of religion as a foundation of morality and this is something that should never be scanted or scoffed at. I do not agree with that particular argument--I am an admirer of Washington, obviously, and of Hamilton--but that strikes me as a little bit of an instrumentalist argument, that we better have religion to keep the peasants in line.
However, I think when Phillip is killed in 1801, Hamilton becomes religious again. A central part of his life is shattered and it is not just the grief that any man would feel if his son died in these circumstances--you always have to remember that in Hamilton's mind is his own father. His own father had left him; had shamed him by leaving. So Hamilton is always trying as a father to be better than James Hamilton. Then Phillip is killed. What does that say? You are not better, you are worse. Your father was a bum, but he never told you anything that got you killed. It must have been a blow that is hard to conceive.
By all accounts and memories of his children, he was devout again at the end of his life. He was probably trying to make sense of what had happened, sort of trying to put his view of the world back together. This is when he thinks of the Christian Constitutional Society. His letters to his wife about his final duel make it plain that his scruples against aiming at Burr are moral and religious ones.