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white. So that neither of these attributes is the genus but an
accident, since we were saying that an accident is an attribute which
can belong to a thing and also not belong.
Moreover, see whether the genus and the species be not found in the
same division, but the one be a substance while the other is a
quality, or the one be a relative while the other is a quality, as
(e.g.) 'slow' and 'swan' are each a substance, while 'white' is not a
substance but a quality, so that 'white' is not the genus either of
'snow' or of 'swan'. Again, knowledge' is a relative, while 'good' and
'noble' are each a quality, so that good, or noble, is not the genus
of knowledge. For the genera of relatives ought themselves also to be
relatives, as is the case with 'double': for multiple', which is the
genus of 'double', is itself also a relative. To speak generally, the
genus ought to fall under the same division as the species: for if the
species be a substance, so too should be the genus, and if the species
be a quality, so too the genus should be a quality; e.g. if white be a
quality, so too should colour be. Likewise, also, in other cases.
Again, see whether it be necessary or possible for the genus to
partake of the object which has been placed in the genus. 'To partake'
is defined as 'to admit the definition of that which is partaken.
Clearly, therefore, the species partake of the genera, but not the
genera of the species: for the species admits the definition of the
genus, whereas the genus does not admit that of the species. You must
look, therefore, and see whether the genus rendered partakes or can
possibly partake of the species, e.g. if any one were to render
anything as genus of 'being' or of 'unity': for then the result will
be that the genus partakes of the species: for of everything that is,
'being' and 'unity' are predicated, and therefore their definition as
well.
Moreover, see if there be anything of which the species rendered is
true, while the genus is not so, e.g. supposing 'being' or 'object of
knowledge' were stated to be the genus of 'object of opinion'. For
'object of opinion' will be a predicate of what does not exist; for
many things which do not exist are objects of opinion; whereas that
'being' or 'object of knowledge' is not predicated of what does not
exist is clear. So that neither 'being' nor 'object of knowledge' is
the genus of 'object of opinion': for of the objects of which the
species is predicated, the genus ought to be predicated as well.
Again, see whether the object placed in the genus be quite unable to
partake of any of its species: for it is impossible that it should
partake of the genus if it do not partake of any of its species,
except it be one of the species reached by the first division: these
do partake of the genus alone. If, therefore, 'Motion' be stated as
the genus of pleasure, you should look and see if pleasure be neither
locomotion nor alteration, nor any of the rest of the given modes of
motion: for clearly you may then take it that it does not partake of
any of the species, and therefore not of the genus either, since what
partakes of the genus must necessarily partake of one of the species
as well: so that pleasure could not be a species of Motion, nor yet be
one of the individual phenomena comprised under the term 'motion'. For
individuals as well partake in the genus and the species, as (e.g.) an
individual man partakes of both 'man' and 'animal'.
Moreover, see if the term placed in the genus has a wider denotation
than the genus, as (e.g.) 'object of opinion' has, as compared with
'being': for both what is and what is not are objects of opinion, so
that 'object of opinion' could not be a species of being: for the
genus is always of wider denotation than the species. Again, see if
the species and its genus have an equal denotation; suppose, for
instance, that of the attributes which go with everything, one were to
be stated as a species and the other as its genus, as for example
Being and Unity: for everything has being and unity, so that neither
is the genus of the other, since their denotation is equal. Likewise,
also, if the 'first' of a series and the 'beginning' were to be placed
one under the other: for the beginning is first and the first is the