The Final Countdown1980

Lasky:
Think of the history of the next forty years...

Commander Richard Owens:
I have a suspicion history will be a little more difficult to beat, than you imagine Mr. Lasky.

Lasky:
I'm talking about the classic paradox of time. Imagine, for example, I go back in time and meet my own Grandfather. Long before he got married, before he had children. And we have an argument, and I kill him. Now if that happens, how am I ever going to be born? And if I can never be born, how can I go back in history and meet my very own Grandfather?

Commander Richard Owens:
[angrily] I'm not half the theorist you are, Mr. Lasky. But I still have a gut instinct that things only happen once. And if they have happened, then there's nothing we can do to change them. Nor should we try.

Lasky:
Well, how are you going to avoid it? It's already happening, and we're already involved!

Commander Dan Thurman:
For Christ's sake! What is this, some half-assed Princeton debating society? We are in a war situation! This is a United States warship! Or, at least, it used to be. Or will be. Or what the hell ever! Oh, Goddammit, you can drive yourself crazy just trying to think about this stuff! [shouts] Jesus, I must be dreaming!