It is better to keep your mouth shut and appear stupid than to open it and remove all doubt.

When in doubt tell the truth.

As to the Adjective; when in doubt, strike it out

When all is said and done, the one sole condition that makes spiritual happiness and preserves it is the absence of doubt

Reputation is a hall-mark: it can remove doubt from pure silver, and it can also make the plated article pass for pure.

It's better to stay silent and look a fool, rather than speak and remove all doubt.