but this seems to be untrue, in spite of the fact that he wrote a book On the Gods, which began:
"With regard to the gods, I cannot feel sure either that they are or that they are not, nor what they
are like in figure; for there are many things that hinder sure knowledge, the obscurity of the
subject and the shortness of human life."
His second visit to Athens is described somewhat satirically in Plato Protagoras, and his doctrines
are discussed seriously in the Theaetetus. He is chiefly noted for his doctrine that "Man is the
measure of all things, of things that are that they are, and of things that are not that they are not."
This is interpreted as meaning that each man is the measure of all things, and that, when men
differ, there is no objective truth in virtue of which one is right and the other wrong. The doctrine
is essentially sceptical, and is presumably based on the "deceitfulness" of the senses.
One of the three founders of pragmatism, F.C.S. Schiller, was in the habit of calling himself a
disciple of Protagoras. This was, I think, because Plato, in the Theaetetus, suggests, as an
interpretation of Protagoras, that one opinion can be better than another, though it cannot be truer.
For example, when a man has jaundice everything looks yellow. There is no sense in saying that
things are really not yellow, but the colour they look to a man in health; we can say, however, that,
since health is better than sickness, the opinion of the man in health is better than that of the man
who has jaundice. This point of view, obviously, is akin to pragmatism.
The disbelief in objective truth makes the majority, for practical purposes, the arbiters as to what
to believe. Hence Protagoras was led to a defence of law and convention and traditional morality.
While, as we saw, he did not know whether the gods existed, he was sure they ought to be
worshipped. This point of view is obviously the right one for a man whose theoretical scepticism
is thoroughgoing and logical.
Protagoras spent his adult life in a sort of perpetual lecture tour through the cities of Greece,
teaching, for a fee, "any one who desired practical efficiency and higher mental culture" ( Zeller,
p. 1299). Plato objects--somewhat snobbishly, according to modern notions-to the Sophists'
practice of charging money for instruction. Plato himself had adequate private means, and was
unable, apparently, to realize the necessities of those who had not his good fortune. It is odd that