There are three sentences of wisdom engraved on the temple of Apollo at Delphi.
Everybody knows the first two:
1. Know thyself (seems dangerous)
2.Everything in moderation. (Yes, I know the joke about that one - everything in moderation including moderation.)
3. The third is more subtle, and seems to be variously translated. It's in the direction of "certainty is dangerous", or "surety leads to ruin," or "certainty is insanity." Seems like a warning about hubris.
The topic came up on an Althouse post.