y not always
to appear useless? For we have already laid down the principle that
things cannot be at one time useful and at another time not, in the same
process.

CRITIAS: But in that respect your argument and mine are the same. For
you maintain if they are useful to a certain end, they can never become
useless; whereas I say that in order to accomplish some results bad
things are needed, and good for others.

SOCRATES: But can a bad thing be used to carry out a good purpose?

CRITIAS: I should say not.

SOCRATES: And we call those actions good which a man does for the sake
of virtue?

CRITIAS: Yes.

SOCRATES: But can a man learn any kind of knowledge which is imparted by
word of mouth if he is wholly deprived of the sense of hearing?

CRITIAS: Certainly not, I think.

SOCRATES: And will not hearing be useful for virtue, if virtue is taught
by hearing and we use the sense of hearing in giving instruction?

CRITIAS: Yes.

SOCRATES: And since medicine frees the sick man from his disease, that
art too may sometimes appear useful in the acquisition of virtue, e.g.
when hearing is procured by the aid of medicine.

CRITIAS: Very likely.

SOCRATES: But if, again, we obtain by wealth the aid of medicine, shall
we not regard wealth as useful for virtue?

CRITIAS: True.

SOCRATES: And also the instruments by which wealth is procured?

CRITIAS: Certainly.

SOCRATES: Then you think that a man may gain wealth by bad and
disgraceful means, and, having obtained the aid of medicine which
enables him to acquire the power of hearing, may use that very faculty
for the acquisition of virtue?

CRITIAS: Yes, I do.

SOCRATES: But can that which is evil be useful for virtue?

CRITIAS: No.

SOCRATES: It is not therefore necessary that the means by which we
obtain what is useful for a certain object should always be useful for
the same object: for it seems that bad actions may sometimes serve good
purposes? The matter will be still plainer if we look at it in this
way:--If things are useful towards the several ends for which they
exist, which ends would not come into existence without them, how would
you regard them? Can ignorance, for instance, be useful for knowledge,
or disease for health, or vice for virtue?

CRITIAS: Never.

SOCRATES: And yet we have already agreed--have we not?--that there
can be no knowledge where there has not previously been ignorance, nor
health where there has not been disease, nor virt