Diogenes Laertius (between 200 and 500 AD) was a Greek biographer. He wrote Lives of Famous Philosophers (Lives, Teachings, and Sayings of Famous Philosophers, also known as Lives and Maxims of Those who Have Distinguished themselves in Philosophy and the Doctrines of Each Sect). He probably wrote it in 240 AD.
In 10 books he wrote about the life of Greek philosophers, but as the case of Protagoras six hundred years after Protagoras' death, and consequently this biographies could not be accurate. The layout of the books is according to philosophical schools. Some scholars say that this work is indispensable for the history of Greece, especially the Hellenistic period.
The whole Book X is dedicated to Epicurus.
SOME say that the study of philosophy originated with the barbarians. In that among the Persians there existed the Magi, and among the Babylonians or Assyrians the Chaldaei, among the Indians the Gymnosophistae, and among the Celts and Gauls men who were called Druids and Semnothei, as Aristotle relates in his book on Magic, and Sotion in the twenty-third book of his Succession of Philosophers. 
- The foundation of every state is the education of its youth.