A dialogue is a discourse consisting of question and answer on some philosophical or political subject, with due regard to the characters of the persons introduced and the choice of diction. The dialectic is the art of discourse by which we either refute or establish some proposition by means of question and answer on the part of the interlocutors.

Anaximander son of Praxiades, of Miletus: he said that the principle and element is the Indefinite, not distinguishing air or water or anything else. … he was the first to discover a gnomon, and he set one up on the Sundials (?) in Sparta, according to Favorinus in his Universal History, to mark solstices and equinoxes; and he also constructed hour indicators. He was the first to draw an outline of earth and sea, but also constructed a [celestial] globe. Of his opinions he made a summary exposition, which I suppose Apollodorus the Athenian also encountered. Apollodorus says in his Chronicles that Anaximander was sixty-four years old in the year of the fifty-eighth Olympiad [547/6 B.C.], and that he died shortly afterwards (having been near his prime approximately during the time of Polycrates, tyrant of Samos).

Anaximenes son of Eurystratus, of Miletus, was a pupil of Anaximander; some say he was also a pupil of Parmenides. He said that the material principle was air and the infinite; and that the stars move, not under the earth, but round it. He used simple and economical Ionic speech. He was active, according to what Apollodorus says, around the time of the capture of Sardis, and died in the 63rd Olympiad.

He (Anaxagoras) is said to have been twenty years old at the time of Xerxes' crossing, and to have lived to seventy-two. Apollodorus says in his Chronicles that he was born in the seventieth Olympiad (500-497 B.C.) and died in the first year of the eighty-eighth (428/7). He began to be a philosopher at Athens in the archonship of Callias (456/5), at the age of twenty, as Demetrius Phalereus tells us in his Register of Archons, and they say he spent thirty years there. … There are different accounts given of his trial. Sotion, in his Succession of Philosophers, says that he was prosecuted by Cleon for impiety, because he maintained that the sun was a red hot mass of metal, and after that Pericles, his pupil, had made a speech in his defence, he was fined five talents and exiled. Satyrus in his Uves, on the other hand, says that the charge was brought by Thucydides in his political campaign against Pericles; and he adds that the charge was not only for the impiety but for Medism as well; and he was condemned to death in his absence. ... Finally he withdrew to Lampsacus, and there died. It is said that when the rulers of the city asked him what privilege he wished to be granted, he replied that the children should be given a holiday every year in the month in which he died. The custom is preserved to the present day. When he died the Lampsacenes buried him with full honours.

The mountains too, at a distance, appear airy masses and smooth, but seen near at hand they are rough.