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pleasure is not good, we shall have produced an argument in both ways,
both universally and in particular, to show that some particular
pleasure is not good. If, on the other hand, the statement made be
definite, it will be possible to demolish it in two ways; e.g. if it
be maintained that it is an attribute of some particular pleasure to
be good, while of some it is not: for whether it be shown that all
pleasure, or that no pleasure, is good, the proposition in question
will have been demolished. If, however, he has stated that only one
single pleasure is good, it is possible to demolish it in three ways:
for by showing that all pleasure, or that no pleasure, or that more
than one pleasure, is good, we shall have demolished the statement in
question. If the statement be made still more definite, e.g. that
prudence alone of the virtues is knowledge, there are four ways of
demolishing it: for if it be shown that all virtue is knowledge, or
that no virtue is so, or that some other virtue (e.g. justice) is so,
or that prudence itself is not knowledge, the proposition in question
will have been demolished.
It is useful also to take a look at individual instances, in cases
where some attribute has been said to belong or not to belong, as in
the case of universal questions. Moreover, you should take a glance
among genera, dividing them by their species until you come to those
that are not further divisible, as has been said before:' for whether
the attribute is found to belong in all cases or in none, you should,
after adducing several instances, claim that he should either admit
your point universally, or else bring an objection showing in what
case it does not hold. Moreover, in cases where it is possible to make
the accident definite either specifically or numerically, you should
look and see whether perhaps none of them belongs, showing e.g. that
time is not moved, nor yet a movement, by enumerating how many species
there are of movement: for if none of these belong to time, clearly it
does not move, nor yet is a movement. Likewise, also, you can show
that the soul is not a number, by dividing all numbers into either odd
or even: for then, if the soul be neither odd nor even, clearly it is
not a number.
In regard then to Accident, you should set to work by means like
these, and in this manner.

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By Aristotle
Written 350 B.C.E Part 1
Next we must go on to examine questions relating to Genus and
Property. These are elements in the questions that relate to
definitions, but dialecticians seldom address their inquiries to these
by themselves. If, then, a genus be suggested for something that is,
first take a look at all objects which belong to the same genus as the
thing mentioned, and see whether the genus suggested is not predicated
of one of them, as happens in the case of an accident: e.g. if 'good'
be laid down to be the genus of 'pleasure', see whether some
particular pleasure be not good: for, if so, clearly good' is not the
genus of pleasure: for the genus is predicated of all the members of
the same species. Secondly, see whether it be predicated not in the
category of essence, but as an accident, as 'white' is predicated of
'snow', or 'self-moved' of the soul. For 'snow' is not a kind of
'white', and therefore 'white' is not the genus of snow, nor is the
soul a kind of 'moving object': its motion is an accident of it, as it
often is of an animal to walk or to be walking. Moreover, 'moving'
does not seem to indicate the essence, but rather a state of doing or
of having something done to it. Likewise, also, 'white': for it
indicates not the essence of snow, but a certain quality of it. So
that neither of them is predicated in the category of 'essence'.
Especially you should take a look at the definition of Accident, and
see whether it fits the genus mentioned, as (e.g.) is also the case in
the instances just given. For it is possible for a thing to be and not
to be self-moved, and likewise, also, for it to be and not to be