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things; and in general, both in demolishing and in establishing an
argument, you should examine things in the light of any resemblance of
whatever description, as we were saying in the case of generation and
destruction. For if what tends to destroy tends to decompose, then
also to be destroyed is to be decomposed: and if what tends to
generate tends to produce, then to be generated is to be produced, and
generation is production. Likewise, also, in the case of the
capacities and uses of things: for if a capacity be a disposition,
then also to be capable of something is to be disposed to it, and if
the use of anything be an activity, then to use it is to be active,
and to have used it is to have been active.
If the opposite of the species be a privation, there are two ways of
demolishing an argument, first of all by looking to see if the
opposite be found in the genus rendered: for either the privation is
to be found absolutely nowhere in the same genus, or at least not in
the same ultimate genus: e.g. if the ultimate genus containing sight
be sensation, then blindness will not be a sensation. Secondly, if
there be a sensation. Secondly, if there be a privation opposed to
both genus and species, but the opposite of the species be not found
in the opposite of the genus, then neither could the species rendered
be in the genus rendered. If, then, you are demolishing a view, you
should follow the rule as stated; but if establishing one there is but
one way: for if the opposite species be found in the opposite genus,
then also the species in question would be found in the genus in
question: e.g. if 'blindness' be a form of 'insensibility', then
'sight' is a form of 'sensation'.
Again, look at the negations of the genus and species and convert the
order of terms, according to the method described in the case of
Accident: e.g. if the pleasant be a kind of good, what is not good is
not pleasant. For were this no something not good as well would then
be pleasant. That, however, cannot be, for it is impossible, if 'good'
be the genus of pleasant, that anything not good should be pleasant:
for of things of which the genus is not predicated, none of the
species is predicated either. Also, in establishing a view, you should
adopt the same method of examination: for if what is not good be not
pleasant, then what is pleasant is good, so that 'good' is the genus
of 'pleasant'.
If the species be a relative term, see whether the genus be a relative
term as well: for if the species be a relative term, so too is the
genus, as is the case with 'double' and 'multiple': for each is a
relative term. If, on the other hand, the genus be a relative term,
there is no necessity that the species should be so as well: for
'knowledge'is a relative term, but not so 'grammar'. Or possibly not
even the first statement would be generally considered true: for
virtue is a kind of 'noble' and a kind of 'good' thing, and yet, while
'virtue' is a relative term, 'good' and 'noble' are not relatives but
qualities. Again, see whether the species fails to be used in the same
relation when called by its own name, and when called by the name of
its genus: e.g. if the term 'double' be used to mean the double of a
'half', then also the term 'multiple' ought to be used to mean
multiple of a 'half'. Otherwise 'multiple' could not be the genus of
'double'.
Moreover, see whether the term fail to be used in the same relation
both when called by the name of its genus, and also when called by
those of all the genera of its genus. For if the double be a multiple
of a half, then 'in excess of 'will also be used in relation to a
'half': and, in general, the double will be called by the names of all
the higher genera in relation to a 'half'. An objection may be raised
that there is no necessity for a term to be used in the same relation
when called by its own name and when called by that of its genus: for
'knowledge' is called knowledge 'of an object', whereas it is called a
'state' and 'disposition' not of an 'object' but of the 'soul'.
Again, see whether the genus and the species be used in the same way
in respect of the inflexions they take, e.g. datives and genitives and