How do you know that what you believe is true? That is the question known as epistemology or the “theory of knowledge.”
I don’t think we can know very much for certain. We have to give up that search. But I do think we can discover how probable a claim to truth is.
I will make a complex issue simple. You can tell whether a claim is probably true by applying the three C’s: correspondence, consistency, and consequences.
Truth is the correspondence of a claim with reality. If what you claim matches reality then what you claim is true. If your claim doesn’t match reality then it is false.
The important question is how do you tell whether or not your belief matches reality? By the objective and verifiable evidence for or against the belief. So the correspondence is mostly about a belief matching the available evidence.
The next test of truth is the consistency of the belief with one’s whole worldview. Contraction is a sign that something is wrong, either the belief is false or part of one’s worldview is false.
The final test of truth is the consequences of accepting the claim as true. If you can live it, it may be false. You will know a claim by its fruits. You don’t get bad results from a good belief, nor do you get good results from a bad belief.
This is a very simple epistemology. It is merely the outline for a larger exploration.