Theaetetus of Athens ( // ; Greek : Θεαίτητος; c. 417 – c. 369 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.
Theaetetus, like Plato, was a student of the Greek mathematician Theodorus of Cyrene. Cyrene was a prosperous Greek colony on the coast of North Africa, in what is now Libya, on the eastern end of the Gulf of Sidra. Theodorus had explored the theory of incommensurable quantities, and Theaetetus continued those studies with great enthusiasm; specifically, he classified various forms of irrational numbers according to the way they are expressed as square roots. This theory is presented in great detail in Book X of Euclid's Elements.
Theaetetus was one of the few Greek mathematicians who was actually a native of Athens. Most Greek mathematicians of antiquity came from the numerous Greek cities scattered around the Ionian coast, the Black Sea and the whole Mediterranean basin.
He evidently resembled Socrates in the snubness of his nose and bulging of his eyes. This and most of what we know of him comes from Plato, who named a dialogue after him, the Theaetetus . He apparently died from wounds and dysentery on his way home after fighting in an Athenian battle at Corinth, now presumed to have occurred in 369 BC; some scholars argue alternately for 391 BC as his date of death, the date of an earlier battle at Corinth.
The crater Theaetetus on the Moon is named after him.
Plato was an Athenian philosopher during the Classical period in Ancient Greece, founder of the Platonist school of thought and the Academy, the first institution of higher learning in the Western world.
Protagoras was a pre-Socratic Greek philosopher and rhetorical theorist. He is numbered as one of the sophists by Plato. In his dialogue Protagoras, Plato credits him with inventing the role of the professional sophist.
This article concerns the period 389 BC – 380 BC.
This article concerns the period 369 BC – 360 BC
The Theaetetus is one of Plato's dialogues concerning the nature of knowledge, written circa 369 BCE.
Ancient Greek philosophy arose in the 6th century BC, at a time when the inhabitants of ancient Greece were struggling to repel devastating invasions from the east. Greek philosophy continued throughout the Hellenistic period and the period in which Greece and most Greek-inhabited lands were part of the Roman Empire. Philosophy was used to make sense out of the world using reason. It dealt with a wide variety of subjects, including astronomy, epistemology, mathematics, political philosophy, ethics, metaphysics, ontology, logic, biology, rhetoric and aesthetics.
Aristides was an ancient Athenian statesman. Nicknamed "the Just", he flourished in the early quarter of Athens' Classical period and is remembered for his generalship in the Persian War. The ancient historian Herodotus cited him as "the best and most honourable man in Athens", and he received similarly reverent treatment in Plato's Socratic dialogues.
Euclid of Megara was a Greek Socratic philosopher who founded the Megarian school of philosophy. He was a pupil of Socrates in the late 5th century BC, and was present at his death. He held the supreme good to be one, eternal and unchangeable, and denied the existence of anything contrary to the good. Editors and translators in the Middle Ages often confused him with Euclid of Alexandria when discussing the latter's Elements.
Hippasus of Metapontum was a Pythagorean philosopher. Little is known about his life or his beliefs, but he is sometimes credited with the discovery of the existence of irrational numbers. The discovery of irrational numbers is said to have been shocking to the Pythagoreans, and Hippasus is supposed to have drowned at sea, apparently as a punishment from the gods for divulging this. However, the few ancient sources which describe this story either do not mention Hippasus by name or alternatively tell that Hippasus drowned because he revealed how to construct a dodecahedron inside a sphere. The discovery of irrationality is not specifically ascribed to Hippasus by any ancient writer.
Theodorus of Cyrene was an ancient Libyan Greek and lived during the 5th century BC. The only first-hand accounts of him that survive are in three of Plato's dialogues: the Theaetetus, the Sophist, and the Statesman. In the former dialogue, he posits a mathematical theorem now known as the Spiral of Theodorus.
Greek mathematics refers to mathematics texts written during and ideas stemming from the Archaic through the Hellenistic and Roman periods, mostly extant from the 7th century BC to the 4th century AD, around the shores of the Eastern Mediterranean. Greek mathematicians lived in cities spread over the entire Eastern Mediterranean from Italy to North Africa but were united by Greek culture and the Greek language. The word "mathematics" itself derives from the Ancient Greek: μάθημα, romanized: máthēmaAttic Greek: [má.tʰɛː.ma]Koine Greek: [ˈma.θi.ma], meaning "subject of instruction". The study of mathematics for its own sake and the use of generalized mathematical theories and proofs is an important difference between Greek mathematics and those of preceding civilizations.
Theaetetus (Θεαίτητος) is a Greek name which could refer to:
Glaucon son of Ariston, was an ancient Athenian and Plato's older brother. He is primarily known as a major conversant with Socrates in the Republic, and the interlocutor during the Allegory of the Cave. He is also referenced briefly in the beginnings of two dialogues of Plato, the Parmenides and Symposium.
This page is a list of topics in ancient philosophy.
Theodorus the Atheist, of Cyrene, was a Greek philosopher of the Cyrenaic school. He lived in both Greece and Alexandria, before ending his days in his native city of Cyrene. As a Cyrenaic philosopher, he taught that the goal of life was to obtain joy and avoid grief, and that the former resulted from knowledge, and the latter from ignorance. However, his principal claim to fame was his alleged atheism. He was usually designated by ancient writers ho atheos, "the atheist."
Socrates was a Greek philosopher from Athens who is credited as one of the founders of Western philosophy, and as being the first moral philosopher of the Western ethical tradition of thought. An enigmatic figure, he authored no texts, and is known chiefly through the accounts of classical writers composing after his lifetime, particularly his students Plato and Xenophon. Other sources include the contemporaneous Antisthenes, Aristippus, and Aeschines of Sphettos. Aristophanes, a playwright, is the main contemporary author to have written plays mentioning Socrates during Socrates' lifetime, although a fragment of Ion of Chios' Travel Journal provides important information about Socrates' youth.
Wilbur Richard Knorr was an American historian of mathematics and a professor in the departments of philosophy and classics at Stanford University. He has been called "one of the most profound and certainly the most provocative historian of Greek mathematics" of the 20th century.
Socrates the Younger was an ancient Athenian philosopher. Ancient texts suggest that he was a young student of the elder Socrates and later a cohort of Plato. He is best remembered for his depiction in Plato's Statesman, and scholars have suggested that he had ties to Academic and Pythagorean philosophy.
This page lists topics related to ancient Greece.