The Complete Aristotle (eng.)

philosophers-i.e. by all, or by the
majority, or by the most notable and illustrious of them. Again
(c), reasoning is ‘contentious’ if it starts from opinions that
seem to be generally accepted, but are not really such, or again if
it merely seems to reason from opinions that are or seem to be
generally accepted. For not every opinion that seems to be
generally accepted actually is generally accepted. For in none of
the opinions which we call generally accepted is the illusion
entirely on the surface, as happens in the case of the principles
of contentious arguments; for the nature of the fallacy in these is
obvious immediately, and as a rule even to persons with little
power of comprehension. So then, of the contentious reasonings
mentioned, the former really deserves to be called ‘reasoning’ as
well, but the other should be called ‘contentious reasoning’, but
not ‘reasoning’, since it appears to reason, but does not really do
so. Further (d), besides all the reasonings we have mentioned there
are the mis-reasonings that start from the premisses peculiar to
the special sciences, as happens (for example) in the case of
geometry and her sister sciences. For this form of reasoning
appears to differ from the reasonings mentioned above; the man who
draws a false figure reasons from things that are neither true and
primary, nor yet generally accepted. For he does not fall within
the definition; he does not assume opinions that are received
either by every one or by the majority or by philosophers-that is
to say, by all, or by most, or by the most illustrious of them-but
he conducts his reasoning upon assumptions which, though
appropriate to the science in question, are not true; for he
effects his mis-reasoning either by describing the semicircles
wrongly or by drawing certain lines in a way in which they could
not be drawn.
    The foregoing must stand for an outline survey of the species of
reasoning. In general, in regard both to all that we have already
discussed and to those which we shall discuss later, we may remark
that that amount of distinction between them may serve, because it
is not our purpose to give the exact definition of any of them; we
merely want to describe them in outline; we consider it quite
enough from the point of view of the line of inquiry before us to
be able to recognize each of them in some sort of way.
     
2
    Next in order after the foregoing, we must say for how many and
for what purposes the treatise is useful. They are
three-intellectual training, casual encounters, and the
philosophical sciences. That it is useful as a training is obvious
on the face of it. The possession of a plan of inquiry will enable
us more easily to argue about the subject proposed. For purposes of
casual encounters, it is useful because when we have counted up the
opinions held by most people, we shall meet them on the ground not
of other people’s convictions but of their own, while we shift the
ground of any argument that they appear to us to state unsoundly.
For the study of the philosophical sciences it is useful, because
the ability to raise searching difficulties on both sides of a
subject will make us detect more easily the truth and error about
the several points that arise. It has a further use in relation to
the ultimate bases of the principles used in the several sciences.
For it is impossible to discuss them at all from the principles
proper to the particular science in hand, seeing that the
principles are the prius of everything else: it is through the
opinions generally held on the particular points that these have to
be discussed, and this task belongs properly, or most
appropriately, to dialectic: for dialectic is a process of
criticism wherein lies the path to the principles of all
inquiries.

Topics, Book II
    Translated by W. A. Pickard-Cambridge
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    div id="book2" class="book" title="Book II">
    1
    Of problems some are universal, others particular. Universal
problems are such as ‘Every pleasure is good’ and ‘No pleasure is
good’; particular problems are such as ‘Some pleasure is good’ and
‘Some pleasure is not good’. The methods of establishing and
overthrowing a view universally are common to both kinds of
problems; for when we have shown that a predicate belongs in every
case, we shall also have shown that it belongs in some cases.
Likewise, also, if we show that it does not belong in any case, we
shall also have shown that it does not belong in every case.