Fallibilism: Thesis about man or human knowledge to the effect that these are fallible - they may be mistaken, even if human beings have good evidence and have done their sincere rational best.
There is much good evidence that fallibilism in the above sense makes sense. And there is also a positive side: Presumed knowledge is corrigible, extendible, partial, incomplete, perfectable, and perhaps outside mathematics and logic never fully certain, precisely because it is revisable. ("What is empirical is not certain. What is certain is not empirical." Einstein.)
Rational men tend to be fallibilists in principle, though they also will insist there are degrees of uncertainty, and more or less fundamental or well-founded theories. But they know they may be mistaken, even in their dearest opinions.
Believers in a faith, fanatics for an ideology, and followers of parties or creeds tend not to be fallibilists where their faith, ideology, party or priests are concerned, which is the reason they often are, in practice if not in their own eyes, totalitarian.
Here is a great experimental physicist on the subject:
"Nothing is more difficult and requires more care than philosophical deduction, nor is there any thing more adverse to its accuracy than fixity of opinion. The man who is certain he is right is almost sure to be wrong; and he has the additional misfortune of inevitably remaining so. All our theories are fixed upon uncertain data, and all of them want alteration and support. Ever since the world began opinion has changed with the progress of things, and it is something more than absurd to suppose that we have a certain claim to perfection; or that we are in the possession of the acme of intellectuality which has, or can result from human thought. Why our successors should not displace us in our opinions, as well as in persons, it is difficult to say; it ever has been so, and from an analogy would be supposed to continue so. And yet with all the practical evidence of the fallibility of our opinions, all and none more than philosophers, are ready to assert the real truth of their opinions."
(Michael Faraday, quoted in L. Pearce Williams)