of Apollonia in Crete, a celebrated natural philosopher who flourished at Athens about 460 B.C. As the pupil of Anaximenes, and contemporary and friend of Anaxagoras, his speculations stand midway between the systems of these philosophers. With Anaximenes he regarded air as the single element of the world, and in this respect he fell short of the dualism of Anaxagoras; but according to him this primal principle existed in various modes, it was especially endowed with intelligence, and in this respect he advanced beyond the pure materialism of Anaximenes. From the identification of intelligence and air, of mind and nature, the next step was obvious, viz., their recognition as distinct independent principles. Of his Diogenes, the famous Cynic philosopher, was the son of Icesias, a money-changer of Sinope in Pontus. Having been detected in adulterating coin, his father and he were compelled to leave their native city. According to another account however, Icesias died in prison, and Diogenes fled to Athens with a single attendant. On his arrival in that city he dismissed his attendant with the quaint question, "If Manes could live without Diogenes, why not Diogenes without him?" and on the same principle he denuded himself of all superfluous dress, furniture, and even ideas. A wooden bowl, which, with his cloak and wallet, formed his only moveables, is said to have been immediately discarded when he saw a boy drinking water from the hollow of his hand. The fame of Antisthenes soon attracted him to Cynosarges, and the pertinacity with which, for the sake of wisdom, he not only endured the scoffs but volunteered to submit to the blows of the great teacher, soon procured him a favourable reception from the whole Cynical school. The favourite pupil, however, soon outstripped his master in the extravagancies of his life, and the pungent keenness of his sarcasms. That he took up his abode in a cask belonging to the temple of Cybele, is a circumstance liable to suspicion, from being more frequently alluded to by the satirists than by the biographers of Diogenes. That he used to inure himself to the vicissitudes of the weather by rolling himself in hot sand in summer, and in winter by embracing statues covered with snow, are facts resting on the authority of all the ancient historians. His numerous witty aphorisms are preserved by Diogenes Laertius. After his voyage to Ægina, during which he fell into the hands of pirates, who sold him as a slave in Crete, the conduct of Diogenes appears in a much less ridiculous light. With characteristic boldness he proclaimed to his captors that he knew no trade except "to govern men," and wished to be sold "to a man that wanted a master." Such a purchaser he seems to have found in Xeniares, who took him to Corinth to superintend the education of his children. Here he spent the rest of his life, and is said to have reached an extreme old age. Here at the Isthmian games he taught the assembled concourse in the Kranion; and hither he attracted a crowd of disciples when Antisthenes had ceased to tickle their ears in Cynosarges. Here, too, in all probability, his famous interview with Alexander took place, in which the only favour he had to beg of the prince was that he would not stand between him and the sun; when Alexander is said to have exclaimed, "If I were not Alexander I would be Diogenes." To Athens Diogenes seems never to have returned. Of his death, which is said to have taken place on the same day with that of Alexander the Great, there are various conflicting accounts. That he perished by the bite of a dog, or from the immoderate use of raw-flesh, or by his own hands, are all generally disbelieved. It is more probable that his death was calm and peaceful; and in spite of his desire to be thrown to the beasts of the field, he received from Xeniares an honourable interment. In the days of Pausanias the Corinthians pointed with pride to his grave; and on the isthmus there was a pillar erected to his memory, on which, as the self-chosen symbol of his life, there rested a dog of Parian marble. His connection with Lais, and the open indecencies of which he is said to have been guilty, have thrown a shade upon his character. The former incident is, however, it must be confessed, exceedingly improbable; and the latter charge was undoubtedly exaggerated, if it was not originated by the shameless excesses of the later Cynics.

It is difficult to give any systematic account of the philosophical opinions of Diogenes. His highest ethical principle was the exercise, or as he usually styled it the gymnastics of the soul, and in carrying out this idea in the family of Xeniares the most honourable part of his life was spent. With him virtue was merely negative, and its most prominent features were resolution and impassibility. With Plato his model state was based on a community of goods and wives. Even in antiquity his opinions seem to have been confounded with those of Diogenes of Apollonia, and works which were undoubtedly spurious were confidently attributed to him. For his relation to Socrates and to the later schools of philosophy, see CYNICISM.

Diogenes Laertius, the biographer of the Greek philosophers, is supposed by some to have received his surname from the town of Laerte in Cilicia, and by others from the Roman family of the Laertii. Of the circumstances of his life we know nothing. The date at which he wrote—probably the reign of Septimius Severus—is known only from conjecture. His own opinions are equally uncertain. By some he was regarded as a Christian; but it seems more probable that he was an Epicurean. The work by which he is known professes to give an account of the lives and sayings of the Greek philosophers. Although it is at best an uncritical and unphilosophical compilation, its value, as giving us an insight into the private life of the Greek sages, justly led Montaigne to exclaim that he wished that instead of one Laertius there had been a dozen. In the commencement of the work he divides philosophers into the Ionic and Italic schools. The biographies of the former begin with Anaximander, and end with Clitomachus, Theophrastus, and Chrysippus; the latter begins with Pythagoras, and ends with Epicurus. The Socratic school, with its various branches, is clasped with the Ionic; while the Eleatics and sceptics are treated under the Italic. The whole of the last book is devoted to Epicurus. From the statements of Burckhardt, the text of Laertius seems to have been much fuller than that which we now possess; and hopes have been entertained of obtaining a more complete copy. The best modern edition is that of Hübler, Leipzig, 2 vols. 8vo, 1828-31.