What word is both the name of Euphronius of the Athenian dem Sunium's son and is also one of Plato's diaglogues concerning the nature of knowledge?
Theaetetus (mathematician) Theaetetus of Athens ( ; Greek: Θεαίτητος ; c. 417 – 368 BC), possibly the son of Euphronius of the Athenian deme Sunium, was a Greek mathematician. His principal contributions were on irrational lengths, which was included in "Book X" of Euclid's "Elements", and proving that there are precisely five regular convex polyhedra. A friend of Socrates and Plato, he is the central character in Plato's eponymous Socratic dialogue.
Dionysius of Chalcedon Dionysius of Chalcedon (fl. 320 BC ) was a Greek philosopher and dialectician connected with the Megarian school. He was a native of Chalcedon on the coast of Bithynia. Dionysius was the person who first used the name "Dialecticians" to describe a splinter group within the Megarian school "because they put their arguments into the form of question and answer". One area of activity for the dialecticians was the framing of definitions, and Aristotle criticises a definition of life by Dionysius in his "Topics":