Soc. And "appears to him" means the same as "he perceives."

  Theaet. True.

  Soc. Then appearing and perceiving coincide in the case of hot and
cold, and in similar instances; for things appear, or may be
supposed to be, to each one such as he perceives them?

  Theaet. Yes.

  Soc. Then perception is always of existence, and being the same as
knowledge is unerring?

  Theaet. Clearly.

  Soc. In the name of the Graces, what an almighty wise man Protagoras
must have been! He spoke these things in a parable to the common herd,
like you and me, but told the truth, his Truth, in secret to his own
disciples.

  Theaet. What do you mean, Socrates?

  Soc. I am about to speak of a high argument, in which all things are
said to be relative; you cannot rightly call anything by any name,
such as great or small, heavy or light, for the great will be small
and the heavy light-there is no single thing or quality, but out of
motion and change and admixture all things are becoming relatively
to one another, which "becoming" is by us incorrectly called being,
but is really becoming, for nothing ever is, but all things are
becoming. Summon all philosophers-Protagoras, Heracleitus, Empedocles,
and the rest of them, one after another, and with the exception of
Parmenides they will agree with you in this. Summon the great
masters of either kind of poetry-Epicharmus, the prince of Comedy, and
Homer of Tragedy; when the latter sings of

     Ocean whence sprang the gods, and mother Tethys,

does he not mean that all things are the offspring, of flux and
motion?

  Theaet. I think so.

  Soc. And who could take up arms against such a great army having
Homer for its general, and not appear ridiculous?

  Theaet. Who indeed, Socrates?

  Soc. Yes, Theaetetus; and there are plenty of other proofs which
will show that motion is the source of what is called being and