butterfly: For every aphorism, there's an equal and opposite one. Like "Out of sight; out of mind" and "Absence makes the heart grow fonder." Or "Many hands make light work" and "Too many cooks spoil the broth."
jic: It's the Law of Conservation of Platitudes!

Speaking of Conservation Laws....

The Law of Conservation of Mass and Energy can be written:
f(t₀) = f(t) for all values of t.

In order for time travel to be possible, either this law is invalid as written, or whenever something is displaced in time (at a rate other than that defined by the light cone), an equal and opposite displacement must occur.