" Survivor—under what conditions?”
“Any conditions. Adaptability, toughness, quickness—those are the things that count most.”
“I think kindness means a lot,” said Sheila timidly.
“It’s a luxury, I’m afraid, though of course it’s such luxuries that make us human,” said Mandelbaum. “Kindness to whom? Sometimes you just have to cut loose and get violent. Some wars are necessary. "

― Poul Anderson , Brain Wave