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all constitute a contrariety. For to do good to friends is contrary to
the doing of evil to friends: for it proceeds from the contrary
disposition, and the one is desirable, and the other objectionable.
The case is the same also in regard to the other conjunctions: for in
each combination the one course is desirable, and the other
objectionable, and the one belongs to a reasonable disposition and the
other to a bad. Clearly, then, from what has been said, the same
course has more than one contrary. For the doing of good to friends
has as its contrary both the doing of good to enemies and the doing of
evil to friends. Likewise, if we examine them in the same way, we
shall find that the contraries of each of the others also are two in
number. Select therefore whichever of the two contraries is useful in
attacking the thesis.
Moreover, if the accident of a thing have a contrary, see whether it
belongs to the subject to which the accident in question has been
declared to belong: for if the latter belongs the former could not
belong; for it is impossible that contrary predicates should belong at
the same time to the same thing.
Or again, look and see if anything has been said about something, of
such a kind that if it be true, contrary predicates must necessarily
belong to the thing: e.g. if he has said that the 'Ideas' exist in us.
For then the result will be that they are both in motion and at rest,
and moreover that they are objects both of sensation and of thought.
For according to the views of those who posit the existence of Ideas,
those Ideas are at rest and are objects of thought; while if they
exist in us, it is impossible that they should be unmoved: for when we
move, it follows necessarily that all that is in us moves with us as
well. Clearly also they are objects of sensation, if they exist in us:
for it is through the sensation of sight that we recognize the Form
present in each individual.
Again, if there be posited an accident which has a contrary, look and
see if that which admits of the accident will admit of its contrary as
well: for the same thing admits of contraries. Thus (e.g.) if he has
asserted that hatred follows anger, hatred would in that case be in
the 'spirited faculty': for that is where anger is. You should
therefore look and see if its contrary, to wit, friendship, be also in
the 'spirited faculty': for if not-if friendship is in the faculty of
desire-then hatred could not follow anger. Likewise also if he has
asserted that the faculty of desire is ignorant. For if it were
capable of ignorance, it would be capable of knowledge as well: and
this is not generally held-I mean that the faculty of desire is
capable of knowledge. For purposes, then, of overthrowing a view, as
has been said, this rule should be observed: but for purposes of
establishing one, though the rule will not help you to assert that the
accident actually belongs, it will help you to assert that it may
possibly belong. For having shown that the thing in question will not
admit of the contrary of the accident asserted, we shall have shown
that the accident neither belongs nor can possibly belong; while on
the other hand, if we show that the contrary belongs, or that the
thing is capable of the contrary, we shall not indeed as yet have
shown that the accident asserted does belong as well; our proof will
merely have gone to this point, that it is possible for it to belong.
Part 8
Seeing that the modes of opposition are four in number, you should
look for arguments among the contradictories of your terms, converting
the order of their sequence, both when demolishing and when
establishing a view, and you should secure them by means of
induction-such arguments (e.g.) as that man be an animal, what is not
an animal is not a man': and likewise also in other instances of
contradictories. For in those cases the sequence is converse: for
'animal' follows upon 'man but 'not-animal' does not follow upon
'not-man', but conversely 'not-man' upon 'not-animal'. In all cases,
therefore, a postulate of this sort should be made, (e.g.) that 'If
the honourable is pleasant, what is not pleasant is not honourable,