Certainty, n.; pl. Certainties.
Etymology: [OF. certaineté.]
1. The quality, state, or condition, of being certain. The certainty of punishment is the truest security against crimes. Fisher Ames.
2. A fact or truth unquestionable established. Certainties are uninteresting and sating. Landor.
3. (Law)
Clearness; freedom from ambiguity; lucidity. Of a certainty, certainly.
Shades of meaning
Fernald has no entry of its own for certainty; he lists it under demonstration.
Where he writes about it:
Demonstration, in the strict and proper sense, is the highest form of proof, and gives the most absolute certainty, but can not be applied outside of pure mathematics or other strictly deductive reasoning; there can be proof and certainty, however, in matters that do not admit of demonstration. — from demonstration
Moral certainty is a conviction resting on such evidence as puts a matter beyond reasonable doubt, while not so irresistible as demonstration. — from demonstration