The Complete Aristotle (eng.)

thing, but
not of another, it is partly false; for it ought to hold of all
reality, if it is said to be of Reality essentially and not
accidentally: as is the case with other relative terms: for every
object of knowledge is a term relative to knowledge: likewise,
also, with other relative terms, inasmuch as all such are
convertible. Moreover, if the right way to render account of a
thing be to render it as it is not in itself but accidentally, then
each and every relative term would be used in relation not to one
thing but to a number of things. For there is no reason why the
same thing should not be both real and white and good, so that it
would be a correct rendering to render the object in relation to
any one whatsoever of these, if to render what it is accidentally
be a correct way to render it. It is, moreover, impossible that a
definition of this sort should be peculiar to the term rendered:
for not only but the majority of the other sciences too, have for
their object some real thing, so that each will be a science of
reality. Clearly, then, such a definition does not define any
science at all; for a definition ought to be peculiar to its own
term, not general.
    Sometimes, again, people define not the thing but only the thing
in a good or perfect condition. Such is the definition of a
rhetorician as ‘one who can always see what will persuade in the
given circumstances, and omit nothing’; or of a thief, as ‘one who
pilfers in secret’: for clearly, if they each do this, then the one
will be a good rhetorician, and the other a good thief: whereas it
is not the actual pilfering in secret, but the wish to do it, that
constitutes the thief.
    Again, see if he has rendered what is desirable for its own sake
as desirable for what it produces or does, or as in any way
desirable because of something else, e.g. by saying that justice is
‘what preserves the laws’ or that wisdom is ‘what produces
happiness’; for what produces or preserves something else is one of
the things desirable for something else. It might be said that it
is possible for what is desirable in itself to be desirable for
something else as well: but still to define what is desirable in
itself in such a way is none the less wrong: for the essence
contains par excellence what is best in anything, and it is better
for a thing to be desirable in itself than to be desirable for
something else, so that this is rather what the definition too
ought to have indicated.
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13
    See also whether in defining anything a man has defined it as an
‘A and B’, or as a ‘product of A and B’ or as an ‘A+B’. If he
defines it as and B’, the definition will be true of both and yet
of neither of them; suppose, e.g. justice to be defined as
‘temperance and courage.’ For if of two persons each has one of the
two only, both and yet neither will be just: for both together have
justice, and yet each singly fails to have it. Even if the
situation here described does not so far appear very absurd because
of the occurrence of this kind of thing in other cases also (for it
is quite possible for two men to have a mina between them, though
neither of them has it by himself), yet least that they should have
contrary attributes surely seems quite absurd; and yet this will
follow if the one be temperate and yet a coward, and the other,
though brave, be a profligate; for then both will exhibit both
justice and injustice: for if justice be temperance and bravery,
then injustice will be cowardice and profligacy. In general, too,
all the ways of showing that the whole is not the same as the sum
of its parts are useful in meeting the type just described; for a
man who defines in this way seems to assert that the parts are the
same as the whole. The arguments are particularly appropriate in
cases where the process of putting the parts together is obvious,
as in a house and other things of that sort: for there, clearly,
you may have the parts and yet not have the whole, so that parts
and whole cannot be the same.
    If, however, he has said that the term being defined is not ‘A
and B’ but the ‘product of A and B’, look and see in the first
place if A and B cannot in the nature of things have a single
product: for some things are so related to one another that nothing
can come of them, e.g. a line and a number. Moreover, see if the
term that has been defined is in the nature of things found
primarily in some single