Heraclitean flux
in Nature was extended to Mind also; only the sensation exists, and
that only at the moment of its occurrence; this alone is truth, this
alone is reality; all else is delusion.

[180]

It followed from this that as a man felt a thing to be, so for him it
veritably was. Thus abstract truth or falsity could not be; the same
statements could be indifferently true or false--to different {88}
individuals at the same time, to the same individual at different
times. It followed that all appearances were equally true: what seemed
to be to any man, that was alone the true for him. The relation of
such a doctrine as this to politics and to morals is not far to seek.
Every man's opinion was as good as another's; if by persuasion you
succeeded in altering a man's opinion, you had not deceived the man,
his new opinion was as true (to him) as the old one. Persuasiveness,
therefore, was the only wisdom. Thus if a man is ill what he eats and
drinks seems bitter to him, and it is so; when he is well it seems the
opposite, and is so. He is not a wiser man in the second state than in
the first, but the second state is pleasanter. If then you can
persuade him that what he thinks bitter is really sweet, you have done
him good. This is what the physician tries to do by his drugs; this is
what the Sophist tries to do by his words. Virtue then is teachable in
so far as it is possible to persuade a boy or a man by rhetoric that
that course of conduct which pleases others is a pleasant course for
him. But if any one happens not to be persuaded of this, and continues
to prefer his own particular course of conduct, this _is_ for him the
good course. You cannot blame him; you cannot say he is wrong. If you
punish him you simply endeavour to supply the dose of unpleasantness
which may {89} be needed to put the balance in his case on the same
side as it already occupies in the case of other people.

It may be worth while to anticipate a little, and insert here in
summary the refutation of this position put into the mouth of Socrates
by Plato in the _Theaetetus_: "But I ought not to conceal from you that
there is a serious objection which may be urged against this doctrine
of Protagoras. For there are states, such as madness and dreaming, in
which perception is false; and half our life is spent in dreaming; and
who can say that at this instant we are not dreaming? Even the fancies
of madmen are real at the time. But