I would agree with Francis Collins that the Moral Law is evidence for the existence of God. We know right from wrong because we have a conscience or a moral compass that gives us guidance. That doesn’t mean we always get it right, but we don’t do actions that stand contrary to the Moral Law as for instance kill someone for kicks, a bit of fun. A psychopath will do so and not because they don’t know right from wrong, but because they have deadened their conscience. I have described how this is done in this post: Biggest stumbling block for me - Hell - #145 by Ani99
Yes, they do have a soul, but their soul is dark. When my late, psychopathic husband confessed who he was and exposed the actions that are done to gain power and influence over others in their lives, I became aware of sheer blackness that seemed to emanate from him. It was not something visual. It was my sudden awareness of his soul. During the talks we had, which lasted for well over two years, I had to glue candles to the table and lite them because I felt a desperate need to see light and though I had all the lights in the house and yard on it was not enough.