Doctor Who: Defining Life

"Pain and loss - they define us as much as happiness or love."*

In the second season, we got to see the Doctor happy and in love and joyous. There were hints of darkness there, but they were kept at bay by the presence of Rose.

( Spoilers through Doctor Who 3x09 -- Family of Blood )

I rewatched Dalek recently and some lines jumped out at me. It was always so clear that the Dalek and the Doctor were meant to be compared, as they do as much in the actual episode ("I know what should happen... exterminate."), but the relationship between the Doctor and Rose and the Dalek and Rose really jumps out to me now.

( some quotes and comparisions )

The Dalek was a soldier. The Doctor was a rebel. With their people gone, neither of them can be what they were before. The Dalek couldn't survive the transition to something new. The Doctor has no more law to rebel against and there is anarchy where there used to be order. He can't afford to be a rebel anymore, but he's never wanted to be a god. And yet... there's no one else. Someone has to be the Doctor, Rose says in The Christmas Invasion. And the Doctor is learning that, in the absence of the Time Lords, someone has to be a watchguard against the perversion of time and the theft of life. He has to be judge, jury, and executioner now, because he thinks there's no one else left.

"I'm so old now. I used to have so much mercy."

( *note; spoilers for S2 )