He's really sort of the devil. He's completely emotionally detached. He has no empathy. You find that in psychopaths. It's about power with Voldemort. It's an aphrodisiac for him. Power makes him feel alive.
“Be as smart as you can, but remember that it is always better to be wise than to be smart.”
“I used to think I had ambition... but now I'm not so sure. It may have been only discontent. They're easily confused.”