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whether it be so of relative opposites and of contraries and of terms
signifying the privation or presence of certain states, and of
contradictory terms. Then, if no clear result be reached so far in
these cases, you should again divide these until you come to those
that are not further divisible, and see (e.g.) whether it be so of
just deeds and unjust, or of the double and the half, or of blindness
and sight, or of being and not-being: for if in any case it be shown
that the knowledge of them is not the same we shall have demolished
the problem. Likewise, also, if the predicate belongs in no case. This
rule is convertible for both destructive and constructive purposes:
for if, when we have suggested a division, the predicate appears to
hold in all or in a large number of cases, we may then claim that the
other should actually assert it universally, or else bring a negative
instance to show in what case it is not so: for if he does neither of
these things, a refusal to assert it will make him look absurd.
Another rule is to make definitions both of an accident and of its
subject, either of both separately or else of one of them, and then
look and see if anything untrue has been assumed as true in the
definitions. Thus (e.g.) to see if it is possible to wrong a god, ask
what is 'to wrong'? For if it be 'to injure deliberately', clearly it
is not possible for a god to be wronged: for it is impossible that God
should be injured. Again, to see if the good man is jealous, ask who
is the 'jealous' man and what is 'jealousy'. For if 'jealousy' is pain
at the apparent success of some well-behaved person, clearly the good
man is not jealous: for then he would be bad. Again, to see if the
indignant man is jealous, ask who each of them is: for then it will be
obvious whether the statement is true or false; e.g. if he is
'jealous' who grieves at the successes of the good, and he is
'indignant' who grieves at the successes of the evil, then clearly the
indignant man would not be jealous. A man should substitute
definitions also for the terms contained in his definitions, and not
stop until he comes to a familiar term: for often if the definition be
rendered whole, the point at issue is not cleared up, whereas if for
one of the terms used in the definition a definition be stated, it
becomes obvious.
Moreover, a man should make the problem into a proposition for
himself, and then bring a negative instance against it: for the
negative instance will be a ground of attack upon the assertion. This
rule is very nearly the same as the rule to look into cases where a
predicate has been attributed or denied universally: but it differs in
the turn of the argument.
Moreover, you should define what kind of things should be called as
most men call them, and what should not. For this is useful both for
establishing and for overthrowing a view: e.g. you should say that we
ought to use our terms to mean the same things as most people mean by
them, but when we ask what kind of things are or are not of such and
such a kind, we should not here go with the multitude: e.g. it is
right to call 'healthy' whatever tends to produce health, as do most
men: but in saying whether the object before us tends to produce
health or not, we should adopt the language no longer of the multitude
but of the doctor.
Part 3
Moreover, if a term be used in several senses, and it has been laid
down that it is or that it is not an attribute of S, you should show
your case of one of its several senses, if you cannot show it of both.
This rule is to be observed in cases where the difference of meaning
is undetected; for supposing this to be obvious, then the other man
will object that the point which he himself questioned has not been
discussed, but only the other point. This commonplace rule is
convertible for purposes both of establishing and of overthrowing a
view. For if we want to establish a statement, we shall show that in
one sense the attribute belongs, if we cannot show it of both senses:
whereas if we are overthrowing a statement, we shall show that in one
sense the attribute does not belong, if we cannot show it of both