Almost everything we do is just an educated guess. The probability of it being correct is a function of our education (for whatever kind of education is applicable).

For example: I guess that when I get out of bed in the morning, my ankles will support my weight. They might not, but for most people, the answer is probably going to be their best guess.

It's easy to see this process in action among young children as another example. They're not born knowing that they won't fall over when they run, then they start assuming they can run safely, then they discovered skinned knees and hands.