Peter Klein: What Is Knowledge? (Gettier Problem) | Who Shaves the Barber? #37

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Peter Klein

What is knowledge?

For some time, the answer to this perennial question was thought by many to be “justified true belief”. If I believe X to be true, I have good reason for believing X to be true, and X really is true, then I know X. In 1963, Edmund Gettier published a now legendary three-page paper titled “Is Justified True Belief Knowledge?” in which he gave two examples of justified true belief that did not constitute knowledge. Since then, epistemologists have mostly agreed that there’s some extra ingredient requisite for knowledge but have disagreed about what it is. After drawing out Gettier’s examples, Peter Klein explains that there are two major camps. The first he calls etiology of belief: theories in which the extra ingredient has to do with how the belief was attained. Reliabilists, for example, argue that a justified true belief counts as knowledge if the belief is arrived at via a method that reliably delivers accurate beliefs. Klein belongs to the second camp: quality of evidence theories, which have to do with the strength of the justification, not the cause of the belief. Klein defends his own preferred quality of evidence theory: defeasibility theory, which involves the existence or absence of “defeaters” for the justification.

Next week: David Papineau: Physicalism

Interested in knowledge? You may be interested in Alvin Plantinga’s epistemology, which I discussed with professor Jim Slagle.

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Special thanks to Jackie Blum for the podcast art, and The Tin Box for the theme music.…

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The Münchhausen Trilemma

There are many forms of radical skepticism: skepticism of the external world, skepticism of other minds, and skepticism of rationality, to name just a few. They arrive at skepticism via different channels, some more successful than others.

Agrippan skepticism is an ancient Greek variety. It is perhaps the hardest-hitting attack on the possibility of knowledge in the history of philosophy. I don’t know of any satisfactory solution.

Epistemologists agree on this much: in order for a belief to count as knowledge, it needs to be at least a justified true belief. What does it mean for a belief to be justified? It means we have a reason for believing it. If this reason will work as justification, it must be a reason that we know.

Of course, if we know this reason, it must be a justified true belief. So what is its justification? It has to be some other reason that we know. And we’re off on a regress.

The problem can be put this way: justification can only happen in three ways:

  • Regress argument: belief A is justified by belief B, which is justified by belief C, which is justified by belief D, and so on.
  • Circular argument: belief A is justified by belief B, which is justified by belief A.
  • Dogmatic argument: belief A is axiomatic. It requires no justification.

None of these options succeed in justifying a belief. Regress arguments fail to justify because they never bottom out at some belief that is already justified.…

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