"Someone sees a slave being whipped, and it doesn't occur to them right away that slavery is wrong. But they go home and think about it, and imagine themselves in the slave's place, and finally think, "No.""

I think lines like this epitomize how messy your approach to understanding human morality as a natural phenomenon is. Richard (the pro), what resources do you recommend I look into to find people taking a more rigorous approach to understanding the phenomenon of human morality (as opposed to promoting a certain type uncritically)?