Comment by mitthrowaway2

Attaching a number to it isn't so daunting, if you view that number as a reflection of your own subjective certainty as to the truth of the proposition. There's no other "correct" number to shoot for; in reality it was either an accident or it wasn't; Nature knows which proposition is true but we don't. Our mission is only to find the figure that minimizes the logarithm of our error, if the truth were at some point to be revealed to us. The more evidence you gather and the more work you put in will get you a better minimum, but there's no reason to be afraid of putting even a rough quantitative number on it before doing that legwork; you'd just be doing it from a state of higher uncertainty, and your stated probability would have to be farther from either confident extreme (0% or 100%) accordingly.