Theaetetus

Theatetus by Plato

I read this dialogue as part of the Online Great Books program. Once again, I am grateful that I am participating in that program because the Theatetus was nowhere on my radar. Having read it, I now see that it is foundational to the Western worldview. I believe that the title of Alvin Plantinga's book “Warranted True Belief” is a nod to the conclusion that Plato and his interlocutor settle on.

The interlocutor in this case is mostly Theatetus, although Theodorus is involved. The story begins with a discussion between Euclides and Terpsion on the occasion of the death of Theatetus in battle. Theatetus was a mathematician who died in the 360s BC. Plato died circa 402 BC. So, this story is about thirty years after the death of Plato (and forty years after the end of the Peloponnesian War.) Euclides has a copy of the discussion between Plato and Theatetus when he was a boy that he has been working on for years.

The discussion is on the subject of “what is knowledge?” Socrates explains that he is the son of a midwife and is himself a midwife of knowledge. His purpose is to midwife Theatetus's understanding of knowledge.

Initially, Theatetus explains that “knowledge” is “perception.” But mere perception can't be knowledge because perception is found in the person (and can be affected by disorders in the perceiving person's perceptions.) On the other hand, knowledge has something to do with truth, and truth is found in the thing perceived.

So, the discussion moves from perception to “judgment.” Things known to the mind are sensible or intelligible. Things are sensible if they are perceived by the sense; things are intelligible if they are known to the intellect. In the intellect we form ideas based on our sense experiences.

A difference between sensation and knowledge is that knowledge can be articulated into propositions and communicated to others. Sensations cannot be so communicated (unless they are first converted into intelligible propositions.) Hit your hand with a hammer and you can form the propositions “that hurts” or “don't hit your hand with hammers.” If you can't do that, the only thing you can do is to hit the other person's hand with a hammer. So, knowledge involves the formation of a judgment about a proposition.

One has knowledge when one applies reason to known, true premises. Presumably, if one uses a reasoning system that preserves truth to true propositions, then one can conclude concludes with certainty that the judgment is true.

Is this enough? No, it is not. Occasionally we can get lucky and stumble on the truth by accident. If you take a multiple-choice question test without knowing the subject and by randomly marking the answer sheet, we don't say you “know” the answers you accidentally got “right.” So, knowledge seems to involve being able to give an account - or as Plantinga says, provide a “warrant” or explanation - for your judgment. In Plato's formulation, the definition of knowledge is provided in this passage:

“SOCRATES: So, it seems, the answer to the question ‘What is knowledge?' will be ‘Correct judgment accompanied by knowledge of the differentness'—for this is what we are asked to understand by the ‘addition of an account.'

Plato. Plato: Complete Works (p. 267). Hackett Publishing Company, Inc.. Kindle Edition.

Of course, this definition of “knowledge” includes the term being defined, which makes it circular in some sense.

Perhaps the answer is that knowledge is not a perfectly closed system. It requires some starting point that itself cannot be proved, such as knowledge of one's own existence.

I didn't read this version of the text. I read a collection of Plato's dialogue. This text seems like a good one in that its introductory essay covers the issues raised in the dialogue.