The way an individual's psychology is intertwined with their morality is the subject of this fascinating book from the pen of the late Ilham Dilman.
Dilman convincingly argues that evil, though it cannot be reduced to psychological terms (it is a moral concept) is explicable in terms of an individual person's psychology. Goodness, by contrast, comes from the person and not their psychology.
Philosophers the world over will want to read this book and see how Dilman skilfully defends his arguments.