The Doctor in “The Age of Steel”

Oh, Lumic, you're a clever man. I'd call you a genius, except I'm in the room. But everything you've invented, you did to fight your sickness. And that's brilliant. That is so human. But once you get rid of sickness and mortality, then what's there to strive for, eh? The Cybermen won't advance, you'll just stop! You'll stay like this forever. A metal Earth with metal men and metal thoughts, lacking the one thing that makes this planet so alive: people! Ordinary, stupid, brilliant people!