All our knowledge is tentative and provisional, and permanently so.
At no stage we can prove that what we now ‘know’ to be true. And it is always possible that it will turn out to be false. Indeed, it is an elementary fact about the intellectual history of mankind (again my favorite example being history and development of theories of Cosmology… one theory building upon and at times contradicting and falsifying previously better theory) that most of what has been ‘known’ at one time or another has eventually turned out to be not the case.
Thus it is a profound mistake to try to do what scientists and philosophers have tried to do (most of the time, anyway), namely prove the truth of a theory, or justify our belief in a theory.
This is to attempt what is logically impossible (Of course many simply don’t get it and hence the confusion and numerous attempts to ‘prove’ the truth of a theory.)
What we can do, however, and this is of the highest possible importance, is to justify our preference for one theory over another.
A look at any current field of science, one will recognize that we will never able to show that our current theory is/was true but we can (and were able to) show that at each stage/each theory of the time was preferable to its preceding theory.