must
resort to a compound term for the genus, such as 'absence of some sort
of difference.' Then _equality_ is absence of difference in quantity;
_sameness_ is often absence of difference in quality, though the usage
is not strict: _likeness_, _similarity_, and _resemblance_, in their
actual use, perhaps, cannot be discriminated; unless _likeness_ be the
more concrete, _similarity_ the more abstract; but they may all be used
compatibly with the recognition of more or less difference in the things
compared, and even imply this. _Identity_ is the absence of difference
of origin, a continuity of existence, with so much sameness from moment
to moment as is compatible with changes in the course of nature; so that
egg, caterpillar, chrysalis, butterfly may be identical for the run of
an individual life, in spite of differences quantitative and
qualitative, as truly as a shilling that all the time lies in a drawer.

Co-ordinate Species, when positive, have the least contrariety; but
there are also opposites, namely, negatives, contradictories and fuller
contraries. These may be regarded as either co-ordinate genera or the
species of co-ordinate genera. Thus, _repose_ being a genus,
_not-repose_ is by dichotomy a co-ordinate genus and is a negative and
contradictory; then _activity_ (implying an end in view), _motion_
(limited to matter), _disturbance_ (implying changes from a state of
calm), _tumult_, etc., are co-ordinate species of _not-repose_, and
are therefore co-ordinate opposites, or contraries, of the species of
_repose_.

As for correlative words, like _master and slave_, _husband and wife_,
etc., it may seem far-fetched to compare them with the sexes of the
same species of plants or animals; but there is this resemblance between
the two cases, that sexual names are correlative, as 'lioness,' and that
one sex of a species, like a correlative name, cannot be defined without
implying the other; for if a distinctive attribute of one sex be
mentioned (as the lion's mane), it is implied that the other wants it,
and apart from this implication the species is not defined: just as the
definition of 'master' implies a 'slave' to obey.

Common words, less precise than the terms of a scientific nomenclature,
differ from them also in this, that the same word may occur in different
genera. Thus, _sleep_ is a species of _repose_ as above; but it is also
a species of _unconsciousness_, with co-ordinate species _swoon_,
_hypnotic