Scully: It's a celebration, but of what?
Mulder: Of something that never happened.
Scully: What? Mulder, this is a photograph. It is a documented moment in time.
Mulder: In a future that somebody is trying like hell to prevent from happening.
Mulder: Think about it, Scully. If Lucas Menand never gets hit by the bus, his complaint gets heard before the grant committee. Jason Nichols loses his funding and he never gets to collaborate on his research with Dr. Yonechi. Therefore, this photograph never gets taken because this celebration never happens.
Scully: Yeah, and if your sister is your aunt and your mother marries your uncle, you'd be your own grandpa.
Mulder: Although common sense may rule out the possibility of time travel, the laws of quantum physics certainly do not. In case you forgot, that's from your graduate thesis. You were a lot more open-minded when you were a youngster.
Mulder: He gave a rather detailed description of the old man.
Scully: What was he wearing, a long black robe and carrying a scythe?