Our abstract thoughts regarding matters of fact are rarely always absolute. Confidence in the truth often can be applied in varying degrees of acceptance. In other words, we can accept something as basically true with some lingering doubt.
Life is a dog you are used to play with by throwing him a stick. You are used to the game, you trust the dog, but one day it doesn’t come back with the stick. Another day even the dog doesn’t return. The man is a master who finds out too late he owned no dog.