"Imagine, if you will, escaping from an opressive society and travelling about with someone you truly, truly love. She dies, and in your haste to try and revive her, you develop a weapon that could turn back time for her and revive her. . . but it ends up destroying a planet. Then you discover that she's not really dead, as she is a Time Lord and you never knew it, because the reason she was along with you was because she was a spy from that opressive society." The Doctor paused.

"I don't condone his reasoning. But I understand it was then that he decided to take over the world in order to balance it, at the cost of free will."