If there is one thing Bayes can teach us to be certain of, however, it is that there is no such thing as absolute certainty of belief. Like a spaceship trying to reach the speed of light, a posterior likelihood can only ever approach 100 percent (or 0 percent). It can never exactly reach it.
And so, anytime we say or think, “I’m absolutely 100 percent certain!” — even for something as probable as our globe-shaped Earth — we’re not only being foolish, we’re being factually wrong. By that statement, we’re effectively saying there is no further evidence in the world, no matter how strong, that could change our minds. And that is as ridiculous as claiming, “I know everything about everything that could ever possibly happen in the universe, ever,” because there are always some unknown unknowns we cannot conceive of, no matter how knowledgeable and wise we think we are.
Liv Boeree, 2018