From this proposition it will follow, when arithmetical addition has been defined, that 1+1=2.

—Principia Mathematica, Volume I, page 360.

A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street.

—David Hilbert

Perfection is when there is no longer anything more to take away.

—Antoine de Saint-Exupery

Set theory can be viewed as a form of exact theology.

—Rudy Rucker

We used to think that if we knew one, we knew two, because one and one are two. We are finding that we must learn a great deal more about 'and.'

—Sir Arthur Eddington

Quotes from homepage of Metamath Proof Explorer.

If it isn't axiomatic you probably shouldn't buy into it, because it likely isn't true, plain and simple.

Be careful out there.