Does Knowing Something Require Absolute Certainty?

In everyday speech, “I know” is often heard as “I cannot be wrong”. If knowledge had to exclude every possibility of error, then weather reports, history, medicine and most scientific knowledge would become doubtful, because new evidence may always require revision.

Fallibilism does not claim that every belief is false, nor is it the same as scepticism. It says that even a true and well-supported judgement may rest on evidence that does not provide an absolute guarantee. Many contemporary epistemologists therefore distinguish knowledge from certainty. Knowledge must be true and cannot be a lucky guess, but the knower need not possess an infallible ground that rules out every possible alternative. Certainty is commonly treated as a higher and stricter epistemic status.

Suppose a normally reliable timetable and live platform information indicate that the next train will arrive in ten minutes, and it does arrive on time. This may amount to fallible knowledge even though an unexpected fault could have defeated the prediction. If the train had not arrived, the original belief would not have been knowledge because it was false; yet that would not show that the earlier evidence was worthless.

My judgement is that the strength of knowledge lies not in claiming permanent immunity from error, but in having sufficiently reliable evidence, remaining open to testing and being corrigible when it fails. Making certainty the threshold for all knowledge turns a rational demand into a standard that is almost unusable.

https://plato.stanford.edu/entries/certainty/
https://iep.utm.edu/fallibil/