Diogenes Laërtius was a historian. He wrote a "history of Greek philosophy", in ten volumes. Very little is known about him as a person. Probably he lived in the 3rd century BC. The last philiosopher found in this work is a student of Sextus Empiricus. Sextus Empiricus lived in the 2nd century. Diogenes Laertius does not list many Roman philiosphers. He also does not talk about Middle Platonism, which must have been popular during that time.