Diogenes Laertius (3rd C. CE)

Diogenes Laertius, native of Laerte in Cilicia, was a biographer of
ancient Greek philosophers. His Lives of the Philosophers (Philosophoi
Biol), in ten books, is still extant and is an important source of
information on the development of Greek philosophy. The period when he
lived is not exactly known, but it is supposed to have been during the
reigns of Septimius Severus and Caracalla. Because of his long and
fairly sympathetic account of Epicurus, some think that Diogenes
belonged to the Epicurean School, but this is not clear. He expresses
his admiration for many philosophers, but his own allegiances, if any,
are not stated.

He divides all the Greek philosophers into two classes: those of the
Ionic and those of the Italic school. He derives the first from
Anaximander, the second from Pythagoras. After Socrates, he divides
the Ionian philosophers into three branches: (a) Plato and the
Academics, down to Clitomachus; (b) the Cynics, down to Chrysippus;
(c) Aristotle and Theophrastus. The series of Italic philosophers
consists, after Pythagoras, of the following: Telanges, Xenophanes,
Parmenides, Zeno of Elea, Leucippus, Democritus, and others down to
Epicurus. The first seven books are devoted to the Ionic philosophers;
the last three treat of the Italic school.

The work of Diogenes is a crude contribution towards the history of
philosophy. It contains a brief account of the lives, doctrines, and
sayings of most persons who have been called philosophers; and though
the author is limited in his philosophical abilities and assessment of
the various schools, the book is valuable as a collection of facts,
which we could not have learned from any other source, and is
entertaining as a sort of pot-pourri on the subject. Diogenes also
includes samples of his own wretched poetry about the philosophers he
discusses.

Diogenes is generally as reliable as whatever source he happens to be
copying from at that moment. Especially when Diogenes is setting down
amusing or scandalous stories about the lives and deaths of various
philosophers which are supposed to serve as fitting illustrations of
their thought, the reader should be wary. The article on Epicurus,
however, is quite valuable, since it contains some original letters of
that philosopher, which comprise a summary of the Epicurean doctrines.