[demosthenes the elder]

"it is better to keep silent and be thought a fool than to speak and remove all doubt" A.Lincoln, I believe.

[Valin]

I stand corrected.
Well actually I'm sitting but you get the idea. :-)

[Dutchgirl]

Not Lincoln...one of your contemporaries...Aesop:
Something about a lion who goes to his advisors and says: "My Queen has complained of the stench in my mouth. Do I have bad breath? "
The first advisor, thinking he wants the truth, agrees that the King has fetid breath, and the lion eats him, for his rudeness.
The second advisor, says his breath smells of dewdrops and honey, and he gets eaten for being a flatterer.
The third advisor, seeing what happened to the first two is struck with a sudden head cold and claims to not be able to give an opinion, since he can't smell.

[Ignatz]

"it is better to keep silent and be thought a fool than to speak and remove all doubt" A.Lincoln, I believe.

It is much older than Lincoln, according to Bartlett's:

Publius Syrus (42 B.C.) Maxim 914. "Let a fool hold his tongue and he will pass for a sage."

Another Publius Syrus maxim I like: "Fortune is not satisfied with inflicting one calamity." - Maxim 274. When it rains, it pours?