The Complete Aristotle (eng.)

by a reference to something else and in
no other way. Thus, a habit is a habit of something, knowledge is
knowledge of something, attitude is the attitude of something. So
it is with all other relatives that have been mentioned. Those
terms, then, are called relative, the nature of which is explained
by reference to something else, the preposition ‘of’ or some other
preposition being used to indicate the relation. Thus, one mountain
is called great in comparison with son with another; for the
mountain claims this attribute by comparison with something. Again,
that which is called similar must be similar to something else, and
all other such attributes have this external reference. It is to be
noted that lying and standing and sitting are particular attitudes,
but attitude is itself a relative term. To lie, to stand, to be
seated, are not themselves attitudes, but take their name from the
aforesaid attitudes.
    It is possible for relatives to have contraries. Thus virtue has
a contrary, vice, these both being relatives; knowledge, too, has a
contrary, ignorance. But this is not the mark of all relatives;
‘double’ and ‘triple’ have no contrary, nor indeed has any such
term.
    It also appears that relatives can admit of variation of degree.
For ‘like’ and ‘unlike’, ‘equal’ and ‘unequal’, have the
modifications ‘more’ and ‘less’ applied to them, and each of these
is relative in character: for the terms ‘like’ and ‘unequal’ bear
‘unequal’ bear a reference to something external. Yet, again, it is
not every relative term that admits of variation of degree. No term
such as ‘double’ admits of this modification. All relatives have
correlatives: by the term ‘slave’ we mean the slave of a master, by
the term ‘master’, the master of a slave; by ‘double’, the double
of its hall; by ‘half’, the half of its double; by ‘greater’,
greater than that which is less; by ‘less,’ less than that which is
greater.
    So it is with every other relative term; but the case we use to
express the correlation differs in some instances. Thus, by
knowledge we mean knowledge the knowable; by the knowable, that
which is to be apprehended by knowledge; by perception, perception
of the perceptible; by the perceptible, that which is apprehended
by perception.
    Sometimes, however, reciprocity of correlation does not appear
to exist. This comes about when a blunder is made, and that to
which the relative is related is not accurately stated. If a man
states that a wing is necessarily relative to a bird, the connexion
between these two will not be reciprocal, for it will not be
possible to say that a bird is a bird by reason of its wings. The
reason is that the original statement was inaccurate, for the wing
is not said to be relative to the bird qua bird, since many
creatures besides birds have wings, but qua winged creature. If,
then, the statement is made accurate, the connexion will be
reciprocal, for we can speak of a wing, having reference
necessarily to a winged creature, and of a winged creature as being
such because of its wings.
    Occasionally, perhaps, it is necessary to coin words, if no word
exists by which a correlation can adequately be explained. If we
define a rudder as necessarily having reference to a boat, our
definition will not be appropriate, for the rudder does not have
this reference to a boat qua boat, as there are boats which have no
rudders. Thus we cannot use the terms reciprocally, for the word
‘boat’ cannot be said to find its explanation in the word ‘rudder’.
As there is no existing word, our definition would perhaps be more
accurate if we coined some word like ‘ruddered’ as the correlative
of ‘rudder’. If we express ourselves thus accurately, at any rate
the terms are reciprocally connected, for the ‘ruddered’ thing is
‘ruddered’ in virtue of its rudder. So it is in all other cases. A
head will be more accurately defined as the correlative of that
which is ‘headed’, than as that of an animal, for the animal does
not have a head qua animal, since many animals have no head.
    Thus we may perhaps most easily comprehend that to which a thing
is related, when a name does not exist, if, from that which has a
name, we derive a new name, and apply it to that with which the
first is reciprocally connected, as in the aforesaid instances,
when we derived the word ‘winged’ from ‘wing’ and from
‘rudder’.
    All relatives, then, if