Thanks to Bill Nichols for this.

*Never make a calculation until you know the answer. Make an estimate before every calculation, try simple physical argument, (symmetry!, invariance!, conservation!) before every derivation, guess the answer to every puzzle. *

*Courage: no one else needs to know what the guess is. Therefore make it quickly, by instinct. a right guess reinforces this instinct. A wrong guess brings the refreshment of surprise. In either case life as a speculative expert, however long, is more fun. *

From Taylor and Wheeler, *Spacetime Physics*, page 60.

The notion that "guesses" are somehow bad is of course wrong. We guess at this all the time. The confidence in our guessing is what the problem is. A "best guess" is qualified with the variance and confidence of the guess.

Without an understanding of the underlying statistics of the domain, it will be difficult to quantify the guess. The credibility of the guesser and the guess will be suspect.