DIOGENES LAERTIUS (or LAERTIUS DIOGENES)  , 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 . He must have lived after Sextus Empiricus (c . A.D . 200), whom he mentions, and before Stephanus of Byzantium (e . A.D . 500), who quotes him . It is probable that he flourished during the reign of Alexander Severus (A.D . 222-235) and his successors . 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 . He treats his subject in two divisions which he describes as the Ionian and the Italian schools; the division is quite unscientific . 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 classed with the Ionic; while the Eleatics and sceptics are treated under the Italic . The whole of the last book is devoted to Epicurus, and contains three most interesting letters addressed to Herodotus, Pythocles and Menoeceus . His chief authorities were Diocles of Magnesia's Cursory Notice ('E7ri.po u) of Philosophers and Favorinus's Miscellaneous History and Memoirs . From the statements of Burlaeus (Walter Burley, a 14th-century monk) in his De vita et moribus philosophorum the text of Diogenes seems to have been much fuller than that which we now possess . In addition to the Lives, Diogenes was the author of a work in verse on famous men, in various metres .