Rhetoric   

arts or systems to guide us, in the hearing of persons who cannot take
in at a glance a complicated argument, or follow a long chain of
reasoning. The subjects of our deliberation are such as seem to
present us with alternative possibilities: about things that could not
have been, and cannot now or in the future be, other than they are,
nobody who takes them to be of this nature wastes his time in
deliberation.
It is possible to form syllogisms and draw conclusions from the
results of previous syllogisms; or, on the other hand, from premisses
which have not been thus proved, and at the same time are so little
accepted that they call for proof. Reasonings of the former kind will
necessarily be hard to follow owing to their length, for we assume an
audience of untrained thinkers; those of the latter kind will fail to
win assent, because they are based on premisses that are not generally
admitted or believed.
The enthymeme and the example must, then, deal with what is in the
main contingent, the example being an induction, and the enthymeme a
syllogism, about such matters. The enthymeme must consist of few
propositions, fewer often than those which make up the normal
syllogism. For if any of these propositions is a familiar fact, there
is no need even to mention it; the hearer adds it himself. Thus, to
show that Dorieus has been victor in a contest for which the prize is
a crown, it is enough to say 'For he has been victor in the Olympic
games', without adding 'And in the Olympic games the prize is a
crown', a fact which everybody knows.
There are few facts of the 'necessary' type that can form the basis of
rhetorical syllogisms. Most of the things about which we make
decisions, and into which therefore we inquire, present us with
alternative possibilities. For it is about our actions that we
deliberate and inquire, and all our actions have a contingent
character; hardly any of them are determined by necessity. Again,
conclusions that state what is merely usual or possible must be drawn
from premisses that do the same, just as 'necessary' conclusions must
be drawn from 'necessary' premisses; this too is clear to us from the
Analytics. It is evident, therefore, that the propositions forming the
basis of enthymemes, though some of them may be 'necessary', will most
of them be only usually true. Now the materials of enthymemes are
Probabilities and Signs, which we can see must correspond respectively
with the propositions that are generally and those that are
necessarily true. A Probability is a thing that usually happens; not,
however, as some definitions would suggest, anything whatever that
usually happens, but only if it belongs to the class of the
'contingent' or 'variable'. It bears the same relation to that in
respect of which it is probable as the universal bears to the
particular. Of Signs, one kind bears the same relation to the
statement it supports as the particular bears to the universal, the
other the same as the universal bears to the particular. The
infallible kind is a 'complete proof' (tekmerhiou); the fallible kind
has no specific name. By infallible signs I mean those on which
syllogisms proper may be based: and this shows us why this kind of
Sign is called 'complete proof': when people think that what they have
said cannot be refuted, they then think that they are bringing forward
a 'complete proof', meaning that the matter has now been demonstrated
and completed (peperhasmeuou); for the word 'perhas' has the same
meaning (of 'end' or 'boundary') as the word 'tekmarh' in the ancient
tongue. Now the one kind of Sign (that which bears to the proposition
it supports the relation of particular to universal) may be
illustrated thus. Suppose it were said, 'The fact that Socrates was
wise and just is a sign that the wise are just'. Here we certainly
have a Sign; but even though the proposition be true, the argument is
refutable, since it does not form a syllogism. Suppose, on the other
hand, it were said, 'The fact that he has a fever is a sign that he is
ill', or, 'The fact that she is giving milk is a sign that she has
lately borne a child'. Here we have the infallible kind of Sign, the