Both angels and demons are ignorant of the future, yet they make predictions. The angels do so when God reveals the future to them and commands them to prophesy, and what they prophesy comes to pass. Demons also make predictions, but these are only guesses based on what they see from afar. John of Damascus
There are no secrets better kept than the secrets everybody guesses. George Bernard Shaw
The best of seers is he who guesses well. Euripides
Let's stop making wild guesses and start gathering data. Poul Anderson
He who guesses well prophesies well. Italian Proverb
The heart is like the astrologer who guesses at the truth. Spanish Proverb