The Complete Aristotle (eng.)

assume the original point, and those of
false cause, and all that treat a number of questions as one: for
in all of them the deception lies in the smallness of the
difference: for our failure to be quite exact in our definition of
‘premiss’ and of ‘proof’ is due to the aforesaid reason.
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8
    Since we know on how many points apparent syllogisms depend, we
know also on how many sophistical syllogisms and refutations may
depend. By a sophistical refutation and syllogism I mean not only a
syllogism or refutation which appears to be valid but is not, but
also one which, though it is valid, only appears to be appropriate
to the thing in question. These are those which fail to refute and
prove people to be ignorant according to the nature of the thing in
question, which was the function of the art of examination. Now the
art of examining is a branch of dialectic: and this may prove a
false conclusion because of the ignorance of the answerer.
Sophistic refutations on the other hand, even though they prove the
contradictory of his thesis, do not make clear whether he is
ignorant: for sophists entangle the scientist as well with these
arguments.
    That we know them by the same line of inquiry is clear: for the
same considerations which make it appear to an audience that the
points required for the proof were asked in the questions and that
the conclusion was proved, would make the answerer think so as
well, so that false proof will occur through all or some of these
means: for what a man has not been asked but thinks he has granted,
he would also grant if he were asked. Of course, in some cases the
moment we add the missing question, we also show up its falsity,
e.g. in fallacies that depend on language and on solecism. If then,
fallacious proofs of the contradictory of a thesis depend on their
appearing to refute, it is clear that the considerations on which
both proofs of false conclusions and an apparent refutation depend
must be the same in number. Now an apparent refutation depends upon
the elements involved in a genuine one: for the failure of one or
other of these must make the refutation merely apparent, e.g. that
which depends on the failure of the conclusion to follow from the
argument (the argument ad impossible) and that which treats two
questions as one and so depends upon a flaw in the premiss, and
that which depends on the substitution of an accident for an
essential attribute, and-a branch of the last-that which depends
upon the consequent: more over, the conclusion may follow not in
fact but only verbally: then, instead of proving the contradictory
universally and in the same respect and relation and manner, the
fallacy may be dependent on some limit of extent or on one or other
of these qualifications: moreover, there is the assumption of the
original point to be proved, in violation of the clause ‘without
reckoning in the original point’. Thus we should have the number of
considerations on which the fallacious proofs depend: for they
could not depend on more, but all will depend on the points
aforesaid.
    A sophistical refutation is a refutation not absolutely but
relatively to some one: and so is a proof, in the same way. For
unless that which depends upon ambiguity assumes that the ambiguous
term has a single meaning, and that which depends on like verbal
forms assumes that substance is the only category, and the rest in
the same way, there will be neither refutations nor proofs, either
absolutely or relatively to the answerer: whereas if they do assume
these things, they will stand, relatively to the answerer; but
absolutely they will not stand: for they have not secured a
statement that does have a single meaning, but only one that
appears to have, and that only from this particular man.
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    div id="section9" class="section" title="9">
9
    The number of considerations on which depend the refutations of
those who are refuted, we ought not to try to grasp without a
knowledge of everything that is. This, however, is not the province
of any special study: for possibly the sciences are infinite in
number, so that obviously demonstrations may be infinite too. Now
refutations may be true as well as false: for whenever it is
possible to demonstrate something, it is also possible to refute
the man who maintains the contradictory of the truth; e.g. if a man
has stated that the diagonal is commensurate with the side of the
square, one might refute him by