to a great
extent, because he himself preferred bringing forward no arguments for
the purpose of persuasion, but wished rather that the person with whom
he was disputing should form his own conclusions from arguments with
which he had furnished himself, and which he was unavoidably compelled
to approve of from the grounds which he had already assented to.

XXXII. And with reference to this kind of persuasion, it appears to me
desirable to lay down a rule, in the first place, that the argument
which we bring forward by way of simile, should be such that it is
impossible to avoid admitting it. For the premiss on account of
which we intend to demand that that point which is doubtful shall be
conceded to us, ought not to be doubtful itself. In the next place, we
must take care that that point, for the sake of establishing which the
induction is made, shall be really like those things which we have
adduced before as matters admitting of no question. For it will be of
no service to us that something has been already admitted, if that for
the sake of which we were desirous to get that statement admitted be
unlike it; so that the hearer may not understand what is the use of
those original inductions, or to what result they tend.

For the man who sees that, if he is correct in giving his assent to
the thing about which he is first asked, that thing also to which he
does not agree must unavoidably be admitted by him, very often will
not allow the examination to proceed any further, either by not
answering at all, or by answering wrongly. Wherefore it is necessary
that he should, by the method in which the inquiry is conducted, be
led on without perceiving it, from the admissions which he has already
made, to admit that which he is not inclined to admit, and at last
he must either decline to give an answer, or he must admit what is
wanted, or he must deny it. If the proposition be denied, then we must
either show its resemblance to those things which have been already
admitted or we must employ some other induction. If it be granted,
then the argumentation may be brought to a close. If he keeps silence,
then an answer must be extracted, or, since silence is very like a
confession, it may be as well to bring the discussion to a close,
taking the silence to be equivalent to an admission.

And so this kind of argumentation is threefold. The first part
consists of one simile, or of several, the second, of that which we
desire to h