And that is how Theology started. People already knew about God in a vague way. Then came a man who claimed to be God; and yet He was not the sort of man you could dismiss as a lunatic. He made them believe Him. They met Him again after they had seen Him killed. And then, after they had been formed into a little society or community, they found God somehow inside them as well: directing them, making them able to do things they could not do before. And when they worked it all out they found they had arrived at the Christian definition of the three-personal God.
Quotes from Mere Christianity, Part 64
C.S. Lewis, Mere Christianity (1952; Harper Collins: 2001) 163.