Doctor: Homo sapiens. What an inventive, invincible species. It's only a few million years since they crawled up out of the mud and learned to walk. Puny, defenceless bipeds. They've survived flood, famine and plague. They've survived cosmic wars and holocausts. And now, here they are, out among the stars, waiting to begin a new life. Ready to outsit eternity. They're indomitable. Indomitable. - THE ARK IN SPACE.
Doctor: Failed? No, not really. You see, I know that although the Daleks will create havoc and destruction for millions of years, I know also that out of their evil must come something good. - GENESIS OF THE DALEKS.
Doctor: Here on Zeta Minor is the boundary between existence as you know it and the other universe which you just don't understand. From the beginning of time it has existed side by side with the known universe. Each is the antithesis of the other. You call it nothing, a word to cover ignorance. And centuries ago scientists invented another word for it. "Antimatter," they called it. And you, by coming here, have crossed the boundary into that other universe to plunder it. Dangerous. - PLANET OF EVIL.
Doctor: Through the millennia, the Time Lords of Gallifrey led a life of ordered calm, protected against all threats from lesser civilisations by their great power. But this was to change. Suddenly and terribly, the Time Lords faced the most dangerous crisis in their long history... - THE DEADLY ASSASSIN.