Diogenes Laertius

Diogenes Laertius was a Greek writer of the third century AD about whose life almost nothing is known; we know only that he wrote the Lives of the Eminent Philosophers. Yet that book preserves a wealth of biography, anecdote, sayings and doctrine of the Greek philosophers, much of it drawn from sources long lost. From Thales to Epicurus, more than eighty philosophers are known to us largely through him, and the three letters and Principal Doctrines of Epicurus survive only because he copied them out in full.