When Nazi alleged war criminals were held in Nuremburg, Captain G. Gilbert was assigned to the prison to serve as their psychologist. He administered Rorschach and IQ tests, and spoke with them at length. He came to the following conclusion:

“In my work with the defendants I was searching for the nature of evil and I now think I have come close to defining it. A lack of empathy. It’s the one characteristic that connects all the defendants, a genuine incapacity to feel with their fellow men. Evil, I think, is the absence of empathy.”