“We have family on Mars. And when you have children, there isn't anything you wouldn't do to protect them."

Doctor: "You'd even allow an innocent person to die?"

"Yes, if I had to."

Doctor: "Well then, that's the difference between us. I'd give up my own life without hesitation; it's mine to give. Just don't ask me to give up anybody else's. ... This is how evil starts: With the belief that the ends justify the means. But once you start down that road, there's no turning back. What if you can save a million lives, but you have to let ten people die? Or a hundred? Or a hundred thousand? Where do you stop?”