In 1872 he was elected master of conferences at the Ecole Normale, and was made doctor of philosophy in recognition of his two treatises, Platonis Hippias Minor sive Socratica contra liberum arbitrium argumenta and La Liberte et le determinisme.
However contemptuous in his portraiture of Hippias and Dionysodorus, however severe in his polemic against Isocrates, Plato regards Protagoras with admiration and Gorgias with respect.
The quadratrix of Dinostratus was well known to the ancient Greek geometers, and is mentioned by Proclus, who ascribes the invention of the curve to a contemporary of Socrates, probably Hippias of Elis.
As supplying a method of doubling the cube), and the curve discovered most probably by Hippias of Elis about 420 B.C., and known by the name rerpaywqouva, or quadratrix.
From the mines of Thrace, and perhaps from the harbour dues and from the mines of Laurium, he derived a large revenue; under his encouragement, Miltiades had planted an Athenian colony on the shores of the Thracian Chersonese; he had even made friends with Thessaly and Macedonia, as is evidenced by the hospitality extended by them to Hippias on his final expulsion.
After a period of disorder and party-feud among the nobles the new constitution was superseded in fact, if not in form, by the autocratic rule of Peisistratus, and his sons Hippias and Hipparchus.
By a former marriage he already had two sons, Hippias and Hipparchus, now growing up, and in his first tyranny or his first exile he married an Argive, Timonassa, by whom he had two other sons Iophon and Hegesistratus, the latter of whom is said to be identical with Thessalus (Ath.
He was the first of its rulers to have relations with other countries; he entered into an alliance with the Peisistratidae, and when Hippias was driven out of Athens he offered him the territory of Anthemus on the Thermaic Gulf, with the object of turning the Greek party feuds to his own advantage (Herodotus v.
Distrusting tradition, he took a few of the finest dialogues as his standard, and from internal evidence denounced as spurious not only those which are generally admitted to be so (Epinomis, Minos, Theages, Arastae, Clitophon, Hipparchus, Eryxias, Letters and Definitions), but also the Meno, Euthydemus, Charmides, Lysis, Laches, First and Second Alcibiades, Hippias Major and Minor, Ion, Euthyphro, Apology, Crito, and even (against Aristotle's explicit assertion) The Laws.