We all, apart from thise with certain abnormal developments, have an inner sense of morality. That is probably genetic. However, what we define as moral and immoral is not universal. It does vary from place to place, time to time, even the same place at different times. There is nothing beyond us that drives and defines morality. It's not a physics law where we can clearly write out what is going on and objectively support our conclusions with mathematics. It's why slavery is ok to some, condemned by others, and because we can reason we can also change out positions from supporting to condemning slavery, or even vice versa. And most people are now living in a world that has widely condemned slavery. We didn't just happen to get that way.