[ubernostrum]

C.S. Peirce, in "The Fixation of Belief", argued that people progress through a series of "methods" of deciding what to believe.

First was the "method of tenacity", which simply consisted of someone believing whatever they had always believed. But this has difficulty as soon as someone runs into a person who believes something different. Who is right?

Next came the "method of authority", deferring to some trusted third party. But again a problem: what happens when that person's social group encounters a different group who follow a different authority?

Next is the "method of a priori", or "method of philosophy", which attempts to deduce the truth from self-evidently true first principles. But of course people may disagree even there.

Finally comes the "method of science", which constantly criticizes and tests itself, knowing and accepting that it is fallible and in need of continuous effort to avoid falling into false conclusions.

Peirce expressed confidence that there is objective truth, but skepticism that any method of human investigation can ever definitively arrive at it. Yet he used this as a definition; truth, he said, is "the opinion which is fated to be ultimately agreed to by all who investigate".