The Complete Aristotle (eng.)

final statement as if
it were the conclusion of such a process, ‘Therefore so-and-so is
not true’, ‘Therefore also so-and-so must be true’-so too in
rhetoric a compact and antithetical utterance passes for an
enthymeme, such language being the proper province of enthymeme, so
that it is seemingly the form of wording here that causes the
illusion mentioned. In order to produce the effect of genuine
reasoning by our form of wording it is useful to summarize the
results of a number of previous reasonings: as ‘some he
saved-others he avenged-the Greeks he freed’. Each of these
statements has been previously proved from other facts; but the
mere collocation of them gives the impression of establishing some
fresh conclusion.
    (b) Another variety is based on the use of similar words for
different things; e.g. the argument that the mouse must be a noble
creature, since it gives its name to the most august of all
religious rites-for such the Mysteries are. Or one may introduce,
into a eulogy of the dog, the dog-star; or Pan, because Pindar
said:
O thou blessed one!
Thou whom they of Olympus call
The hound of manifold shape
That follows the Mother of Heaven:
    or we may argue that, because there is much disgrace in there
not being a dog about, there is honour in being a dog. Or that
Hermes is readier than any other god to go shares, since we never
say ‘shares all round’ except of him. Or that speech is a very
excellent thing, since good men are not said to be worth money but
to be worthy of esteem-the phrase ‘worthy of esteem’ also having
the meaning of ‘worth speech’.
    2. Another line is to assert of the whole what is true of the
parts, or of the parts what is true of the whole. A whole and its
parts are supposed to be identical, though often they are not. You
have therefore to adopt whichever of these two lines better suits
your purpose. That is how Euthydemus argues: e.g. that any one
knows that there is a trireme in the Peiraeus, since he knows the
separate details that make up this statement. There is also the
argument that one who knows the letters knows the whole word, since
the word is the same thing as the letters which compose it; or
that, if a double portion of a certain thing is harmful to health,
then a single portion must not be called wholesome, since it is
absurd that two good things should make one bad thing. Put thus,
the enthymeme is refutative; put as follows; demonstrative: ‘For
one good thing cannot be made up of two bad things.’ The whole line
of argument is fallacious. Again, there is Polycrates’ saying that
Thrasybulus put down thirty tyrants, where the speaker adds them up
one by one. Or the argument in the Orestes of Theodectes, where the
argument is from part to whole:
‘Tis right that she who slays her lord should die.
    ‘It is right, too, that the son should avenge his father. Very
good: these two things are what Orestes has done.’ Still, perhaps
the two things, once they are put together, do not form a right
act. The fallacy might also be said to be due to omission, since
the speaker fails to say by whose hand a husband-slayer should
die.
    3. Another line is the use of indignant language, whether to
support your own case or to overthrow your opponent’s. We do this
when we paint a highly-coloured picture of the situation without
having proved the facts of it: if the defendant does so, he
produces an impression of his innocence; and if the prosecutor goes
into a passion, he produces an impression of the defendant’s guilt.
Here there is no genuine enthymeme: the hearer infers guilt or
innocence, but no proof is given, and the inference is fallacious
accordingly.
    4. Another line is to use a ‘Sign’, or single instance, as
certain evidence; which, again, yields no valid proof. Thus, it
might be said that lovers are useful to their countries, since the
love of Harmodius and Aristogeiton caused the downfall of the
tyrant Hipparchus. Or, again, that Dionysius is a thief, since he
is a vicious man-there is, of course, no valid proof here; not
every vicious man is a thief, though every thief is a vicious
man.
    5. Another line represents the accidental as essential. An
instance is what Polycrates says of the mice, that they ‘came to
the rescue’ because they gnawed through the bowstrings. Or it might
be maintained that an invitation to dinner is a great honour, for
it was because he was not invited that Achilles was ‘angered’ with
the Greeks at Tenedos? As a