clearly follows that the species must be in two non-subaltern
genera. Or perhaps it is not impossible for the same differentia to be
used of two non-subaltern genera, and we ought to add the words
'except they both be subordinate members of the same genus'. Thus
'walking animal' and 'flying animal' are non-subaltern genera, and
'biped' is the differentia of both. The words 'except they both be
subordinate members of the same genus' ought therefore to be added;
for both these are subordinate to 'animal'. From this possibility,
that the same differentia may be used of two non-subaltern genera,
it is clear also that there is no necessity for the differentia to
carry with it the whole of the genus to which it belongs, but only the
one or the other of its limbs together with the genera that are higher
than this, as 'biped' carries with it either 'flying' or 'walking
animal'.
See, too, if he has rendered 'existence in' something as the
differentia of a thing's essence: for the general view is that
locality cannot differentiate between one essence and another.
Hence, too, people condemn those who divide animals by means of the
terms 'walking' and 'aquatic', on the ground that 'walking' and
'aquatic' indicate mere locality. Or possibly in this case the censure
is undeserved; for 'aquatic' does not mean 'in' anything; nor does
it denote a locality, but a certain quality: for even if the thing
be on the dry land, still it is aquatic: and likewise a land-animal,
even though it be in the water, will still be a and not an
aquatic-animal. But all the same, if ever the differentia does
denote existence in something, clearly he will have made a bad
mistake.
Again, see if he has rendered an affection as the differentia: for
every affection, if intensified, subverts the essence of the thing,
while the differentia is not of that kind: for the differentia is
generally considered rather to preserve that which it
differentiates; and it is absolutely impossible for a thing to exist
without its own special differentia: for if there be no 'walking',
there will be no 'man'. In fact, we may lay down absolutely that a
thing cannot have as its differentia anything in respect of which it
is subject to alteration: for all things of that kind, if intensified,
destroy its essence. If, then, a man has rendered any differentia of
this kind, he has made a mistake: for we undergo absolutely no
alteration in respect of our differentiae.
Again, see if he has failed to render the differentia of a
relative term relatively to something else; for the differentiae of
relative terms are themselves relative, as in the case also of
knowledge. This is classed as speculative, practical and productive;
and each of these denotes a relation: for it speculates upon
something, and produces something and does something.
Look and see also if the definer renders each relative term
relatively to its natural purpose: for while in some cases the
particular relative term can be used in relation to its natural
purpose only and to nothing else, some can be used in relation to
something else as well. Thus sight can only be used for seeing, but
a strigil can also be used to dip up water. Still, if any one were
to define a strigil as an instrument for dipping water, he has made
a mistake: for that is not its natural function. The definition of a
thing's natural function is 'that for which it would be used by the
prudent man, acting as such, and by the science that deals specially
with that thing'.
Or see if, whenever a term happens to be used in a number of
relations, he has failed to introduce it in its primary relation: e.g.
by defining 'wisdom' as the virtue of 'man' or of the 'soul,' rather
than of the 'reasoning faculty': for 'wisdom' is the virtue
primarily of the reasoning faculty: for it is in virtue of this that
both the man and his soul are said to be wise.
Moreover, if the thing of which the term defined has been stated
to be an affection or disposition, or whatever it may be, be unable to
admit it, the definer has made a mistake. For every disposition and
every affection is formed naturally in that of which it is an
affection or disposition, as knowledge, too, is formed in the soul,
being a disposition of soul. Sometimes, however, people make bad
mistakes in matters of this sort, e.g. all those who say that
'sleep' is a 'failure of sensation', or that 'perplexity' is a state
of 'equality between contrary reasonings', or that 'pain' is a
'violent disruption of parts that are naturally conjoined'. For
sleep is not an attribute of sensation, whereas it ought to be, if
it is a failure of sensation. Likewise, perplexity is not an attribute
of opposite reasonings, nor pain of parts naturally conjoined: for
then inanimate things will be in pain, since pain will be present in
them. Similar in character, too, is the definition of 'health', say,
as a 'balance of hot and cold elements': for then health will be
necessarily exhibited by the hot and cold elements: for balance of
anything is an attribute inherent in those things of which it is the
balance, so that health would be an attribute of them. Moreover,
people who define in this way put effect for cause, or cause for
effect. For the disruption of parts naturally conjoined is not pain,
but only a cause of pain: nor again is a failure of sensation sleep,
but the one is the cause of the other: for either we go to sleep
because sensation fails, or sensation fails because we go to sleep.
Likewise also an equality between contrary reasonings would be
generally considered to be a cause of perplexity: for it is when we
reflect on both sides of a question and find everything alike to be in
keeping with either course that we are perplexed which of the two we
are to do.
Moreover, with regard to all periods of time look and see whether
there be any discrepancy between the differentia and the thing
defined: e.g. supposing the 'immortal' to be defined as a 'living
thing immune at present from destruction'. For a living thing that
is immune 'at present' from destruction will be immortal 'at present'.
Possibly, indeed, in this case this result does not follow, owing to
the ambiguity of the words 'immune at present from destruction': for
it may mean either that the thing has not been destroyed at present,
or that it cannot be destroyed at present, or that at present it is
such that it never can be destroyed. Whenever, then, we say that a
living thing is at present immune from destruction, we mean that it is
at present a living thing of such a kind as never to be destroyed: and
this is equivalent to saying that it is immortal, so that it is not
meant that it is immortal only at present. Still, if ever it does
happen that what has been rendered according to the definition belongs
in the present only or past, whereas what is meant by the word does
not so belong, then the two could not be the same. So, then, this
commonplace ru
le ought to be followed, as we have said.
7
You should look and see also whether the term being defined is
applied in consideration of something other than the definition
rendered. Suppose (e.g.) a definition of 'justice' as the 'ability
to distribute what is equal'. This would not be right, for 'just'
describes rather the man who chooses, than the man who is able to
distribute what is equal: so that justice could not be an ability to
distribute what is equal: for then also the most just man would be the
man with the most ability to distribute what is equal.
Moreover, see if the thing admits of degrees, whereas what is
rendered according to the definition does not, or, vice versa, what is
rendered according to the definition admits of degrees while the thing
does not. For either both must admit them or else neither, if indeed
what is rendered according to the definition is the same as the thing.
Moreover, see if, while both of them admit of degrees, they yet do not
both become greater together: e.g. suppose sexual love to be the
desire for intercourse: for he who is more intensely in love has not a
more intense desire for intercourse, so that both do not become
intensified at once: they certainly should, however, had they been the
same thing.
Moreover, suppose two things to be before you, see if the term to be
defined applies more particularly to the one to which the content of
the definition is less applicable. Take, for instance, the
definition of 'fire' as the 'body that consists of the most rarefied
particles'. For 'fire' denotes flame rather than light, but flame is
less the body that consists of the most rarefied particles than is
light: whereas both ought to be more applicable to the same thing,
if they had been the same. Again, see if the one expression applies
alike to both the objects before you, while the other does not apply
to both alike, but more particularly to one of them.
Moreover, see if he renders the definition relative to two things
taken separately: thus, the beautiful' is 'what is pleasant to the
eyes or to the ears": or 'the real' is 'what is capable of being acted
upon or of acting'. For then the same thing will be both beautiful and
not beautiful, and likewise will be both real and not real. For
'pleasant to the ears' will be the same as 'beautiful', so that 'not
pleasant to the ears' will be the same as 'not beautiful': for of
identical things the opposites, too, are identical, and the opposite
of 'beautiful' is 'not beautiful', while of 'pleasant to the ears' the
opposite is not pleasant to the cars': clearly, then, 'not pleasant to
the ears' is the same thing as 'not beautiful'. If, therefore,
something be pleasant to the eyes but not to the ears, it will be both
beautiful and not beautiful. In like manner we shall show also that
the same thing is both real and unreal.
Moreover, of both genera and differentiae and all the other terms
rendered in definitions you should frame definitions in lieu of the
terms, and then see if there be any discrepancy between them.
8
If the term defined be relative, either in itself or in respect of
its genus, see whether the definition fails to mention that to which
the term, either in itself or in respect of its genus, is relative,
e.g. if he has defined 'knowledge' as an 'incontrovertible conception'
or 'wishing' as 'painless conation'. For of everything relative the
essence is relative to something else, seeing that the being of
every relative term is identical with being in a certain relation to
something. He ought, therefore, to have said that knowledge is
'conception of a knowable' and that wishing is 'conation for a
good'. Likewise, also, if he has defined 'grammar' as 'knowledge of
letters': whereas in the definition there ought to be rendered
either the thing to which the term itself is relative, or that,
whatever it is, to which its genus is relative. Or see if a relative
term has been described not in relation to its end, the end in
anything being whatever is best in it or gives its purpose to the
rest. Certainly it is what is best or final that should be stated,
e.g. that desire is not for the pleasant but for pleasure: for this is
our purpose in choosing what is pleasant as well.
Look and see also if that in relation to which he has rendered the
term be a process or an activity: for nothing of that kind is an
end, for the completion of the activity or process is the end rather
than the process or activity itself. Or perhaps this rule is not
true in all cases, for almost everybody prefers the present experience
of pleasure to its cessation, so that they would count the activity as
the end rather than its completion.
Again see in some cases if he has failed to distinguish the quantity
or quality or place or other differentiae of an object; e.g. the
quality and quantity of the honour the striving for which makes a
man ambitious: for all men strive for honour, so that it is not enough
to define the ambitious man as him who strives for honour, but the
aforesaid differentiae must be added. Likewise, also, in defining
the covetous man the quantity of money he aims at, or in the case of
the incontinent man the quality of the pleasures, should be stated.
For it is not the man who gives way to any sort of pleasure whatever
who is called incontinent, but only he who gives way to a certain kind
of pleasure. Or again, people sometimes define night as a 'shadow on
the earth', or an earthquake as a movement of the earth', or a cloud
as 'condensation of the air', or a wind as a 'movement of the air';
whereas they ought to specify as well quantity, quality, place, and
cause. Likewise, also, in other cases of the kind: for by omitting any
differentiae whatever he fails to state the essence of the term. One
should always attack deficiency. For a movement of the earth does
not constitute an earthquake, nor a movement of the air a wind,
irrespective of its manner and the amount involved.
Moreover, in the case of conations, and in any other cases where
it applies, see if the word 'apparent' is left out, e.g. 'wishing is a
conation after the good', or 'desire is a conation after the
pleasant'-instead of saying 'the apparently good', or 'pleasant'.
For often those who exhibit the conation do not perceive what is
good or pleasant, so that their aim need not be really good or
pleasant, but only apparently so. They ought, therefore, to have
rendered the definition also accordingly. On the other hand, any one
who maintains the existence of Ideas ought to be brought face to
face with his Ideas, even though he does render the word in
question: for there can be no Idea of anything merely apparent: the
general view is that an Idea is always spoken of in relation to an
Idea: thus absolute desire is for the absolutely pleasant, and
absolute wishing is for the absolutely good; they therefore cannot
be for an apparent good or an apparently pleasant: for the existence
of an absolut
ely-apparently-good or pleasant would be an absurdity.
9
Moreover, if the definition be of the state of anything, look at
what is in the state, while if it be of what is in the state, look
at the state: and likewise also in other cases of the kind. Thus if
the pleasant be identical with the beneficial, then, too, the man
who is pleased is benefited. Speaking generally, in definitions of
this sort it happens that what the definer defines is in a sense
more than one thing: for in defining knowledge, a man in a sense
defines ignorance as well, and likewise also what has knowledge and
what lacks it, and what it is to know and to be ignorant. For if the
first be made clear, the others become in a certain sense clear as
well. We have, then, to be on our guard in all such cases against
discrepancy, using the elementary principles drawn from
consideration of contraries and of coordinates.
Moreover, in the case of relative terms, see if the species is
rendered as relative to a species of that to which the genus is
rendered as relative, e.g. supposing belief to be relative to some
object of belief, see whether a particular belief is made relative
to some particular object of belief: and, if a multiple be relative to
a fraction, see whether a particular multiple be made relative to a
particular fraction. For if it be not so rendered, clearly a mistake
has been made.
See, also, if the opposite of the term has the opposite
definition, whether (e.g.) the definition of 'half' is the opposite of
that of 'double': for if 'double' is 'that which exceeds another by an
equal amount to that other', 'half' is 'that which is exceeded by an
amount equal to itself'. In the same way, too, with contraries. For to
the contrary term will apply the definition that is contrary in some
one of the ways in which contraries are conjoined. Thus (e.g.) if
'useful'='productive of good', 'injurious'=productive of evil' or
'destructive of good', for one or the other of thee is bound to be
contrary to the term originally used. Suppose, then, neither of