o grow again. There come to me also those who have
nothing in them, and have no need of my art; and I am their matchmaker
(see above), and marry them to Prodicus or some other inspired sage who
is likely to suit them. I tell you this long story because I suspect
that you are in labour. Come then to me, who am a midwife, and the son
of a midwife, and I will deliver you. And do not bite me, as the women
do, if I abstract your first-born; for I am acting out of good-will
towards you; the God who is within me is the friend of man, though he
will not allow me to dissemble the truth. Once more then, Theaetetus,
I repeat my old question--"What is knowledge?" Take courage, and by the
help of God you will discover an answer.' 'My answer is, that knowledge
is perception.' 'That is the theory of Protagoras, who has another way
of expressing the same thing when he says, "Man is the measure of all
things." He was a very wise man, and we should try to understand him.
In order to illustrate his meaning let me suppose that there is the same
wind blowing in our faces, and one of us may be hot and the other cold.
How is this? Protagoras will reply that the wind is hot to him who is
cold, cold to him who is hot. And "is" means "appears," and when you
say "appears to him," that means "he feels." Thus feeling, appearance,
perception, coincide with being. I suspect, however, that this was only
a "facon de parler," by which he imposed on the common herd like you and
me; he told "the truth" (in allusion to the title of his book, which
was called "The Truth") in secret to his disciples. For he was really
a votary of that famous philosophy in which all things are said to be
relative; nothing is great or small, or heavy or light, or one, but all
is in motion and mixture and transition and flux and generation, not
"being," as we ignorantly affirm, but "becoming." This has been the
doctrine, not of Protagoras only, but of all philosophers, with the
single exception of Parmenides; Empedocles, Heracleitus, and others, and
all the poets, with Epicharmus, the king of Comedy, and Homer, the king
of Tragedy, at their head, have said the same; the latter has these
words--

"Ocean, whence the gods sprang, and mother Tethys."

And many arguments are used to show, that motion is the source of life,
and rest of death: fire and warmth are produced by friction, and living
creatures owe their origin to a similar cause; the bodily frame is
preserved by exercise