Time travel
From MAlf
When someone travels through time, they are able to screw their grandmother before they were even born. A phenomonen known as Doing the nasty in the pasty.
This happened to Julian Bashir when he traveled backwards in time to meet his grandmother. He did not screw her, and when he returned, he found out he was never born. But because he was never born, he could not have not screwed her, and thus could not be born. therefore he was born so he could go back in time to not screw her.
