Diogenes Laertius (Διογένης ὁ Λαέρτιος) was a biographer of Greek philosophers, likely active in the first half of the 3rd century CE [1][2]. His name suggests origins in Laerte in Cilicia or Crete, though this remains uncertain [1]. He dedicated his major work to a woman interested in Plato, indicating he moved within educated circles [1].

His extant work is the Lives and Opinions of Eminent Philosophers (Βίοι καὶ γνῶμαι τῶν ἐν φιλοσοφίᾳ εὐδοκιμησάντων), a ten-book compilation. He also wrote the Pammetros (Πάμμετρος), a lost collection of poems by philosophers [1][3].

Diogenes Laertius is a principal source for the history of ancient Greek philosophy. His compilation preserves biographies, doctrines, and anecdotes for over eighty philosophers, drawing from many now-lost sources [1][2]. While criticized for a lack of critical analysis, his work is indispensable, especially for understanding Hellenistic schools like the Epicureans, whose three surviving letters he alone preserved [1][2].

Sources 1. Stanford Encyclopedia of Philosophy: Diogenes Laertius: https://plato.stanford.edu/entries/diogenes-laertius/ 2. Internet Encyclopedia of Philosophy: Diogenes Laertius: https://iep.utm.edu/diogenes-laertius/ 3. Encyclopædia Britannica: Diogenes Laertius: https://www.britannica.com/biography/Diogenes-Laertius