The Complete Aristotle (eng.)

Broadly speaking, however, the only sort of
person who can strictly be called a judge is the man who decides
the issue in some matter of public controversy; that is, in law
suits and in political debates, in both of which there are issues
to be decided. In the section on political oratory an account has
already been given of the types of character that mark the
different constitutions.
    The manner and means of investing speeches with moral character
may now be regarded as fully set forth.
    Each of the main divisions of oratory has, we have seen, its own
distinct purpose. With regard to each division, we have noted the
accepted views and propositions upon which we may base our
arguments-for political, for ceremonial, and for forensic speaking.
We have further determined completely by what means speeches may be
invested with the required moral character. We are now to proceed
to discuss the arguments common to all oratory. All orators,
besides their special lines of argument, are bound to use, for
instance, the topic of the Possible and Impossible; and to try to
show that a thing has happened, or will happen in future. Again,
the topic of Size is common to all oratory; all of us have to argue
that things are bigger or smaller than they seem, whether we are
making political speeches, speeches of eulogy or attack, or
prosecuting or defending in the law-courts. Having analysed these
subjects, we will try to say what we can about the general
principles of arguing by ‘enthymeme’ and ‘example’, by the addition
of which we may hope to complete the project with which we set out.
Of the above-mentioned general lines of argument, that concerned
with Amplification is-as has been already said-most appropriate to
ceremonial speeches; that concerned with the Past, to forensic
speeches, where the required decision is always about the past;
that concerned with Possibility and the Future, to political
speeches.
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    Let us first speak of the Possible and Impossible. It may
plausibly be argued: That if it is possible for one of a pair of
contraries to be or happen, then it is possible for the other: e.g.
if a man can be cured, he can also fall ill; for any two contraries
are equally possible, in so far as they are contraries. That if of
two similar things one is possible, so is the other. That if the
harder of two things is possible, so is the easier. That if a thing
can come into existence in a good and beautiful form, then it can
come into existence generally; thus a house can exist more easily
than a beautiful house. That if the beginning of a thing can occur,
so can the end; for nothing impossible occurs or begins to occur;
thus the commensurability of the diagonal of a square with its side
neither occurs nor can begin to occur. That if the end is possible,
so is the beginning; for all things that occur have a beginning.
That if that which is posterior in essence or in order of
generation can come into being, so can that which is prior: thus if
a man can come into being, so can a boy, since the boy comes first
in order of generation; and if a boy can, so can a man, for the man
also is first. That those things are possible of which the love or
desire is natural; for no one, as a rule, loves or desires
impossibilities. That things which are the object of any kind of
science or art are possible and exist or come into existence. That
anything is possible the first step in whose production depends on
men or things which we can compel or persuade to produce it, by our
greater strength, our control of them, or our friendship with them.
That where the parts are possible, the whole is possible; and where
the whole is possible, the parts are usually possible. For if the
slit in front, the toe-piece, and the upper leather can be made,
then shoes can be made; and if shoes, then also the front slit and
toe-piece. That if a whole genus is a thing that can occur, so can
the species; and if the species can occur, so can the genus: thus,
if a sailing vessel can be made, so also can a trireme; and if a
trireme, then a sailing vessel also. That if one of two things
whose existence depends on each other is possible, so is the other;
for instance, if ‘double’, then ‘half’, and if ‘half’, then
‘double’. That if a thing can be produced without art or
preparation, it can be produced still more certainly by the careful
application of art to it. Hence Agathon has said:
To some things we by art must needs attain,
Others by destiny or