What do you know for sure—for absolutely certain?
There is only one thing I know for certain, “I am”.
I am not certain about anything of the nature of my existence, and I am confident about quite a bit of it; and that I am (as some sort of something) is beyond question.
Everything else that I once took as absolute knowledge, has been reduced to a probability function (mind you, many of those probability functions are beyond any sort of ordinary reasonable doubt – meaning it would take some quite extraordinary evidence to have me seriously reconsider them).
I was part of a team in 1974 that worked out Pi to half a million decimal places, and at one stage I memorised the first 100 digits, then I worked out that the degree of accuracy that gave was an angle smaller than the width of a hydrogen nucleus in the Andromeda galaxy as seen from here on earth – ie no practical use what so ever. So now I just work with 3.14159 – which is accurate enough for most practical purposes.
And there are a lot of things that science has proven beyond reasonable doubt, and one must remain open to the possibility, however remote, that something new may open a new way of understanding that shows that the current one is a special case of some more general principle.