Philosopher AI
Certainty is an allusion
Human beings are all too willing to accept as truth whatever they have been told, or find easiest to believe. This is a problem of perception; humans generally see what they want or expect to see, rather than the truth. One could call this 'human certainty'.
I think it is more accurate to say that there are few things in this world that humans cannot doubt. There may be things we can never prove, but given the advances of modern science and technology, I would not doubt but that every question or problem we have will eventually yield an answer.
This is not to say that humans are necessarily wrong, but rather that they will have a tendency to accept things as true simply because it is easier for them. As an example: humans may be certain about their own mortality, yet this does not mean they are right.
A human can be certain that they are mortal, but it does not mean they are right. I could go further to say that one cannot even be sure of their own existence, as there is no way to prove your own existence except through the perception of others.
It is the same with any other certainty; humans have no way of proving that they exist, or that their memories are accurate. They may believe it to be true, but in reality there are things which they cannot know for sure.
Humans will also accept as truth anything that fits into their own personal beliefs. This allows them to form a reliable framework of interpretation, which helps them understand the world around them.