How is Ben Franklin a Rationalist?

In this autobiography, Ben Franklin tells us how many faults that he has in is life that he wants to change. In the passage he quoted," I wished to live without any fault at any time," But unlike a puritan, he wants to figure out human nature scientifically. Not let god figure everything out. That is how he is a rationalist. He made a chart of how he could improve his life. He basically did an experiment on himself.