Look, that's why there's rules, understand? So that you think before you break 'em.

The three rules of the Librarians of Time and Space are: 1) Silence; 2) Books must be returned no later than the date last shown; and 3) Do not interfere with the nature of causality.

Christ managed to boil down an awful lot of commandments to a few very simple rules for living. It's when you go backwards through the 'begats' and the Garden of Eden, and you start thinking, 'Hang on, that's a big punishment for eating one lousy apple... There's a human-rights issue.'

They say you have to abide by the rules, but they change the rules every month.

Wizard's Seventh Rule
Life is the future, not the past.

It cannot be said often enough that science fiction as a genre is incredibly educational - and I'm speaking the written science fiction, not 'Star Trek.' Science fiction writers tend to fill their books if they're clever with little bits of interesting stuff and real stuff.