foregoing-i.e. neither a definition nor a property nor a genus yet
belongs to the thing: (something which may possibly either belong or
not belong to any one and the self-same thing, as (e.g.) the
'sitting posture' may belong or not belong to some self-same thing.
Likewise also 'whiteness', for there is nothing to prevent the same
thing being at one time white, and at another not white. Of the
definitions of accident the second is the better: for if he adopts the
first, any one is bound, if he is to understand it, to know already
what 'definition' and 'genus' and 'property' are, whereas the second
is sufficient of itself to tell us the essential meaning of the term
in question. To Accident are to be attached also all comparisons of
things together, when expressed in language that is drawn in any
kind of way from what happens (accidit) to be true of them; such as,
for example, the question, 'Is the honourable or the expedient
preferable?' and 'Is the life of virtue or the life of self-indulgence
the pleasanter?', and any other problem which may happen to be phrased
in terms like these. For in all such cases the question is 'to which
of the two does the predicate in question happen (accidit) to belong
more closely?' It is clear on the face of it that there is nothing
to prevent an accident from becoming a temporary or relative property.
Thus the sitting posture is an accident, but will be a temporary
property, whenever a man is the only person sitting, while if he be
not the only one sitting, it is still a property relatively to those
who are not sitting. So then, there is nothing to prevent an
accident from becoming both a relative and a temporary property; but a
property absolutely it will never be.

                                 6

  We must not fail to observe that all remarks made in criticism of
a 'property' and 'genus' and 'accident' will be applicable to
'definitions' as well. For when we have shown that the attribute in
question fails to belong only to the term defined, as we do also in
the case of a property, or that the genus rendered in the definition
is not the true genus, or that any of the things mentioned in the
phrase used does not belong, as would be remarked also in the case
of an accident, we shall have demolished the definition; so that, to
use the phrase previously employed,' all the points we have enumerated
might in a certain sense be called 'definitory'. But we must not on
this account expect to find a single line of inquiry which will
apply universally to them all: for this is not an easy thing to
find, and, even were one found, it would be very obscure indeed, and
of little service for the treatise before us. Rather, a special plan
of inquiry must be laid down for each of the classes we have
distinguished, and then, starting from the rules that are
appropriate in each case, it will probably be easier to make our way
right through the task before us. So then, as was said before,' we
must outline a division of our subject, and other questions we must
relegate each to the particular branch to which it most naturally
belongs, speaking of them as 'definitory' and 'generic' questions. The
questions I mean have practically been already assigned to their
several branches.

                                 7

  First of all we must define the number of senses borne by the term
'Sameness'. Sameness would be generally regarded as falling, roughly
speaking, into three divisions. We generally apply the term
numerically or specifically or generically-numerically in cases
where there is more than one name but only one thing, e.g. 'doublet'
and 'cloak'; specifically, where there is more than one thing, but
they present no differences in respect of their species, as one man
and another, or one horse and another: for things like this that
fall under the same species are said to be 'specifically the same'.
Similarly, too, those things are called generically the same which
fall under the same genus, such as a horse and a man. It might
appear that the sense in which water from the same spring is called
'the same water' is somehow different and unlike the senses
mentioned above: but really such a case as this ought to be ranked
in the same class with the things that in one way or another are
called 'the same' in view of unity of species. For all such things
seem to be of one family and to resemble one another. For the reaon
why all water is said to be specifically the same as all other water
is because of a certain likeness it bears to it, and the only
difference in the case of water drawn from the same spring is this,
that the likeness is more emphatic: that is why we do not
distinguish it from the things that in one way or another are called
'the same' in view of unity of species. It is generally supposed
that the term 'the same' is most used in a sense agreed on by every
one when applied to what is numerically one. But even so, it is apt to
be rendered in more than one sense; its most literal and primary use
is found whenever the sameness is rendered in reference to an
alternative name or definition, as when a cloak is said to be the same
as a doublet, or an animal that walks on two feet is said to be the
same as a man: a second sense is when it is rendered in reference to a
property, as when what can acquire knowledge is called the same as a
man, and what naturally travels upward the same as fire: while a third
use is found when it is rendered in reference to some term drawn
from Accident, as when the creature who is sitting, or who is musical,
is called the same as Socrates. For all these uses mean to signify
numerical unity. That what I have just said is true may be best seen
where one form of appellation is substituted for another. For often
when we give the order to call one of the people who are sitting down,
indicating him by name, we change our description, whenever the person
to whom we give the order happens not to understand us; he will, we
think, understand better from some accidental feature; so we bid him
call to us 'the man who is sitting' or 'who is conversing over
there'-clearly supposing ourselves to be indicating the same object by
its name and by its accident.