From the Beginning to Plato

FROM THE BEGINNING TO PLATO 229
probably died after 421 BC. According to one tradition he was educated as a boy
under Persian religious teachers at his house in Thrace. He probably first visited
Athens well before 443 BC, as in that year he was asked by Pericles to frame a
constitution for the new pan-Hellenic colony of Thurii in southern Italy. It is clear
that throughout his life Protagoras was able to rely on the support of Pericles. He
was said to have died by drowning on a sea-voyage, when he had to leave
Athens after he had been tried and convicted of impiety. As a result of his trial it
was recorded that his books were burnt in the agora after they had been called in
from those who possessed them, by a herald’s proclamation. The immediate
basis for the charge of impiety seems to have been his work On the Gods, of
which the opening words were:
concerning the gods, I cannot know either that [or perhaps ‘how’] they
exist or do not exist or what they are like in appearance, for there are many
things which prevent one’s knowing: the obscurity of the subject and the
shortness of human life.
(DK 80 B4)
As a result Protagoras came to be included in later lists of alleged atheists from
the sophistic period, alongside Prodicus, Critias, Euripides, Anaxagoras and
Phidias. It seems more probable however that Protagoras’ position was actually
one of agnosticism rather than outright atheism.
Diogenes Laertius, who wrote probably in the third century AD, lists twelve
works as written by Protagoras and from other later writers we can add a further
six titles. The tradition of the discussion and interpretation of Protagoras’ most
important doctrines begins with Plato, above all in the dialogues Protagoras and
Theaetetus. But all we have by way of actual fragments of Protagoras’ writings
is a handful of brief statements and single sentences, and it is not possible to form
any certain idea of the arrangement and order of the arguments in his writings.
What must be done is to attempt a reconstruction of his doctrines on the basis of
the doxographic tradition, and we have good reason to suppose that the
doxographic tradition as a whole was ultimately rooted in what Protagoras had
actually written.
By far the most famous of his doctrines is that known by the catch-phrase as
the homo mensura or man the measure theory. This was stated in the first
sentence of a work entitled On Truth, perhaps with a subtitle Overthrowing
Arguments. The fragment reads, ‘Of all things man is the measure, of things that
are that [or perhaps “how”] they are and of things that are not that [or “how”]
they are not (DK 80 B1).’ Every feature of this famous sentence has been the
subject of vigorous controversies, and there is no agreement among scholars as to
its precise meaning. In what follows I attempt to state the main matters of
controversy and to suggest what seem to me to be the most likely interpretations.
In the nineteenth century quite a number of scholars took the word ‘man’ in the
quotation to mean not the individual human being but mankind as a whole, and