Dr. Rodney McKay: Let me ask you a question. Say there's a runaway train. It's hurtling out of control towards ten people standing in the middle of the tracks. The only way to save those people is to flip a switch - send the train down another set of tracks. The only problem is there is a baby in the middle of those tracks.
Teyla Emmagan: Why would anyone leave a baby in harm's way like that?
Dr. Rodney McKay: I don't know. That's not the point. Look, it's an ethical dilemma. Look, Katie Brown brought it up over dinner the other night. The question is: is it appropriate to divert the train and kill the one baby to save the ten people?
Ronon Dex: Wouldn't the people just see the train coming and move?
Dr. Rodney McKay: No. No, they wouldn't see it.
Ronon Dex: Why not?
Dr. Rodney McKay: Well... Look, I dunno. Say they're blind.
Teyla Emmagan: *All* of them?
Dr. Rodney McKay: Yes, all of them.
Ronon Dex: Then why don't you just call out and tell them to move out of the way?
Dr. Rodney McKay: Well, because they can't hear you.
Lt. Colonel John Sheppard: What, they're deaf too?
[Rodney throws him a look]
Lt. Colonel John Sheppard: How fast is the train going?
Dr. Rodney McKay: Look, the speed doesn't matter!
Lt. Colonel John Sheppard: Well, sure it does. If it's goin' slow enough, you could outrun it and shove everyone to the side.
Ronon Dex: Or better yet, go get the baby.
Dr. Rodney McKay: For God's sake! I was just trying to...