our intercourse with our fellow-men this or that stratagem is employed
by one side or the other. By finding out the common elements in tricks
repeated in different forms, we shall be enabled to exhibit certain
general stratagems which may be advantageous, as well for our own use,
as for frustrating others if they use them.

[Footnote 1: Diogenes Laertes tells us that among the numerous
writings on Rhetoric by Theophrastus, all of which have been lost,
there was one entitled [Greek: Agonistikon taes peri tous eristikous
gogous theorias.] That would have been just what we want.]

What follows is to be regarded as a first attempt.


THE BASIS OF ALL DIALECTIC.

First of all, we must consider the essential nature of every dispute:
what it is that really takes place in it.

Our opponent has stated a thesis, or we ourselves,--it is all one.
There are two modes of refuting it, and two courses that we may
pursue.

I. The modes are (1) _ad rem_, (2) _ad hominem_ or _ex concessis_.
That is to say: We may show either that the proposition is not in
accordance with the nature of things, i.e., with absolute, objective
truth; or that it is inconsistent with other statements or admissions
of our opponent, i.e., with truth as it appears to him. The latter
mode of arguing a question produces only a relative conviction, and
makes no difference whatever to the objective truth of the matter.