The Complete Aristotle (eng.)

the genus has a contrary, the species has none;
for if the genus be contrary to anything, so too is the species, as
virtue to vice and justice to injustice.
    Likewise. also, if one were to look at other instances, one
would come to see clearly a fact like this. An objection may be
raised in the case of health and disease: for health in general is
the contrary of disease, whereas a particular disease, being a
species of disease, e.g. fever and ophthalmia and any other
particular disease, has no contrary.
    If, therefore, you are demolishing a view, there are all these
ways in which you should make your examination: for if the
aforesaid characters do not belong to it, clearly what has been
rendered is not the genus. If, on the other hand, you are
establishing a view, there are three ways: in the first place, see
whether the contrary of the species be found in the genus stated,
suppose the genus have no contrary: for if the contrary be found in
it, clearly the species in question is found in it as well.
Moreover, see if the intermediate species is found in the genus
stated: for whatever genus contains the intermediate contains the
extremes as well. Again, if the genus have a contrary, look and see
whether also the contrary species is found in the contrary genus:
for if so, clearly also the species in question is found in the
genus in question.
    Again, consider in the case of the inflexions and the
co-ordinates of species and genus, and see whether they follow
likewise, both in demolishing and in establishing a view. For
whatever attribute belongs or does not belong to one belongs or
does not belong at the same time to all; e.g. if justice be a
particular form of knowledge, then also ‘justly’ is ‘knowingly’ and
the just man is a man of knowledge: whereas if any of these things
be not so, then neither is any of the rest of them.
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4
    Again, consider the case of things that bear a like relation to
one another. Thus (e.g.) the relation of the pleasant to pleasure
is like that of the useful to the good: for in each case the one
produces the other. If therefore pleasure be a kind of ‘good’, then
also the pleasant will be a kind of ‘useful’: for clearly it may be
taken to be productive of good, seeing that pleasure is good. In
the same way also consider the case of processes of generation and
destruction; if (e.g.) to build be to be active, then to have built
is to have been active, and if to learn be to recollect, then also
to have learnt is to have recollected, and if to be decomposed be
to be destroyed, then to have been decomposed is to have been
destroyed, and decomposition is a kind of destruction. Consider
also in the same way the case of things that generate or destroy,
and of the capacities and uses of 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