Lives of the Eminent Philosophers by Diogenes Laertius, translated from the Greek by Pamela Mensch, edited by James Miller Oxford University Press, 676 pp., $45.00

Poor Diogenes Laertius. He gets no respect. A “perfect ass”—“asinus germanus”—one nineteenth-century scholar called him. “Dim-witted,” said Nietzsche. An “ignoramus,” declared the twentieth-century classicist Werner Jaeger. In his lyric moods he wrote “perhaps the worst verses ever published,” an anthologist pronounced. And he had “no talent for philosophical exposition,” declares The Oxford Companion to Philosophy.

Then why waste time on him? For this excellent reason: Diogenes Laertius compiled the sole extant work from antiquity that gives anything like a comprehensive picture of Greek and Hellenistic philosophy. He may have been a flaming mediocrity. He may have been credulous and intellectually shallow. He may have produced a scissors-and-paste job cribbed from other ancient sources. But those other sources are lost, which makes what Diogenes Laertius left behind, to quote the Routledge Encyclopedia of Philosophy, “truly priceless.” Eighty percent of success is showing up, Woody Allen supposedly said. Well, Lives of the Eminent Philosophers showed up. And by dint of that, its author has become what Nietzsche called “the night watchman of the history of Greek philosophy: no one can enter into it unless he has given him the key.”

What made this fellow so lucky? It’s not hard to explain why certain works survive. We still have Plato’s dialogues because they were diligently preserved by the Academy. Aristotle too founded a school, and his treatises were widely copied and studied. (Still, the nineteen or so dialogues Aristotle composed—esteemed for their literary quality by Cicero as “a river of flowing gold”—were somehow mislaid by Western civilization.) But Diogenes Laertius didn’t have a school, as far as anyone knows. In fact, almost nothing is known about the man. Even his slightly absurd Greco-Roman name is a puzzle—was “Laertius” some kind of nickname? Judging from the historical references in Lives (which stop just short of the Neoplatonists), he probably lived early in the third century CE. There is a hint in his text that he might have been a native of the eastern city of Nicea. Beyond that he is a cipher. That his work should endure, when the vast majority of the philosophical writings he drew on perished, may simply have been a “quirk of fate”—so guesses James Miller, the editor of this welcome new translation.

If so, it was not an altogether unhappy quirk. Despite the ridicule to which he has been subjected, Diogenes Laertius has some undeniable virtues. It is true that he shows little interest in, and scant understanding of, actual philosophical reasoning. But he is keenly attuned to the philosopher as a social type, and an eccentric one at that. Philosophy to him was not a mere body of propositions; it was a way of life, one that pretended to be superior to conventional modes of…