PREFACE.

DIOGENES, the author of the following work, was a native—as is generally believed—of Laërte, in Cilicia, from which he derived the surname of Laërtius. Little is known of him personally, nor is the age in which he lived clearly established. However, since Plutarch, Sextus Empiricus, and Saturninus are among the writers he quotes, he is generally believed to have lived near the end of the second century of our era, although some place him in the time of Alexander Severus, and others as late as Constantine. His work consists of ten books, variously titled: The Lives of Philosophers, A History of Philosophy, and The Lives of Sophists. From internal evidence (III. 47, 29), we learn that he wrote it for a noble lady (according to some, Arria; according to others, Julia, the Empress of Severus), who occupied herself with the study of philosophy, and especially of Plato.

Diogenes Laërtius divides Greek philosophy into the Ionic school, beginning with Anaximander and ending with Theophrastus (in which class he includes the Socratic philosophy and all its various branches), and the Italian school, beginning with Pythagoras and ending with Epicurus, in which he includes the Eleatics, as well as Heraclitus and the Sceptics. From the minute consideration he devotes to Epicurus and his system, it has been supposed that he himself belonged to that school.

His work is the chief source of information we possess