Diogenes Laërtius'

Diogenes Laërtius (/daɪˈɒdʒɪniːz leɪˈɜːrʃiəs/;Greek: Διογένης Λαέρτιος, Diogenēs Laertios; fl. 3rd century AD) was a biographer of the Greek philosophers. Nothing is definitively known about his life, but his surviving Lives and Opinions of Eminent Philosophers is a principal source for the history of Greek philosophy. "Diogenes has acquired an importance out of all proportion to his merits because the loss of many primary sources and of the earlier secondary compilations has accidentally left him the chief continuous source for the history of Greek philosophy."

Although not definitive, Laërtius must have lived after Sextus Empiricus (c. 200), whom he mentions, and before Stephanus of Byzantium and Sopater of Apamea (c. 500), who quote him. His work makes no mention of Neoplatonism, even though it is addressed to a woman who was "an enthusiastic Platonist". Hence he is assumed to have flourished in the first half of the 3rd century, during the reign of Alexander Severus (222–235) and his successors.

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