How Do Duties Come From Without a Personal God?

In the variance of Hinduism that don't believe in a personal God, it's awfully hard to see where duties could come from. Unfortunately, there's not a lot of Hindus which have got into the realm of philosophy of religion. I know some of your YouTube videos have dealt with some of the testimony that people have given that they can recall prior lives. How does that work and how credible do you believe that is?