personality is a soul.
It is mentioned often that when a person is born, that is something unique inside him. It is as unique as the physical markings in his body - the fingerprints, and the brain patterns. It can only be described through manifestations, which is through actions.
Ethics is the way the teacher ( author ) tells the only thing you will bring in your death. This is why when a person dies, one unique person is removed from this world. Much more grievous evil is to kill someone who is about to enter this world. This is why we call that "evil nature" or sin and guilt is the pang that comes after it.