by Aristotle
to their truth, but for dialectic only with an eye to general opinion.
All propositions should be taken in their most universal form; then,
the one should be made into many. E.g. 'The knowledge of opposites
is the same'; next, 'The knowledge of contraries is the same', and
that 'of relative terms'. In the same way these two should again be
divided, as long as division is possible, e.g. the knowledge of
'good and evil', of 'white and black', or 'cold and hot'. Likewise
also in other cases.
15
On the formation, then, of propositions, the above remarks are
enough. As regards the number of senses a term bears, we must not only
treat of those terms which bear different senses, but we must also try
to render their definitions; e.g. we must not merely say that
justice and courage are called 'good' in one sense, and that what
conduces to vigour and what conduces to health are called so in
another, but also that the former are so called because of a certain
intrinsic quality they themselves have, the latter because they are
productive of a certain result and not because of any intrinsic
quality in themselves. Similarly also in other cases.
Whether a term bears a number of specific meanings or one only,
may be considered by the following means. First, look and see if its
contrary bears a number of meanings, whether the discrepancy between
them be one of kind or one of names. For in some cases a difference is
at once displayed even in the names; e.g. the contrary of 'sharp' in
the case of a note is 'flat', while in the case of a solid edge it
is 'dull'. Clearly, then, the contrary of 'sharp' bears several
meanings, and if so, also does 'sharp'; for corresponding to each of
the former terms the meaning of its contrary will be different. For
'sharp' will not be the same when contrary to 'dull' and to 'flat',
though 'sharp' is the contrary of each. Again Barhu ('flat',
'heavy') in the case of a note has 'sharp' as its contrary, but in the
case of a solid mass 'light', so that Barhu is used with a number of
meanings, inasmuch as its contrary also is so used. Likewise, also,
'fine' as applied to a picture has 'ugly' as its contrary, but, as
applied to a house, 'ramshackle'; so that 'fine' is an ambiguous term.
In some cases there is no discrepancy of any sort in the names used,
but a difference of kind between the meanings is at once obvious: e.g.
in the case of 'clear' and 'obscure': for sound is called 'clear'
and 'obscure', just as 'colour' is too. As regards the names, then,
there is no discrepancy, but the difference in kind between the
meanings is at once obvious: for colour is not called 'clear' in a
like sense to sound. This is plain also through sensation: for of
things that are the same in kind we have the same sensation, whereas
we do not judge clearness by the same sensation in the case of sound
and of colour, but in the latter case we judge by sight, in the former
by hearing. Likewise also with 'sharp' and 'dull' in regard to
flavours and solid edges: here in the latter case we judge by touch,
but in the former by taste. For here again there is no discrepancy
in the names used, in the case either of the original terms or of
their contraries: for the contrary also of sharp in either sense is
'dull'.
Moreover, see if one sense of a term has a contrary, while another
has absolutely none; e.g. the pleasure of drinking has a contrary in
the pain of thirst, whereas the pleasure of seeing that the diagonal
is incommensurate with the side has none, so that 'pleasure' is used
in more than one sense. To 'love' also, used of the frame of mind, has
to 'hate' as its contrary, while as used of the physical activity
(kissing) it has none: clearly, therefore, to 'love' is an ambiguous
term. Further, see in regard to their intermediates, if some
meanings and their contraries have an intermediate, others have
none, or if both have one but not the same one, e.g. 'clear' and
'obscure' in the case of colours have 'grey' as an intermediate,
whereas in the case of sound they have none, or, if they have, it is
'harsh', as some people say that a harsh sound is intermediate.
'Clear', then, is an ambiguous term, and likewise also 'obscure'. See,
moreover, if some of them have more than one intermediate, while
others have but one, as is the case with 'clear' and 'obscure', for in
the case of colours there are numbers of intermediates, whereas in
regard to sound there is but one, viz. 'harsh'.
Again, in the case of the contradictory opposite, look and see if it
bears more than one meaning. For if this bears more than one
meaning, then the opposite of it also will be used in more than one
meaning; e.g. 'to fail to see' a phrase with more than one meaning,
viz. (1) to fail to possess the power of sight, (2) to fail to put
that power to active use. But if this has more than one meaning, it
follows necessarily that 'to see' also has more than one meaning:
for there will be an opposite to each sense of 'to fail to see';
e.g. the opposite of 'not to possess the power of sight' is to possess
it, while of 'not to put the power of sight to active use', the
opposite is to put it to active use.
Moreover, examine the case of terms that denote the privation or
presence of a certain state: for if the one term bears more than one
meaning, then so will the remaining term: e.g. if 'to have sense' be
used with more than one meaning, as applied to the soul and to the
body, then 'to be wanting in sense' too will be used with more than
one meaning, as applied to the soul and to the body. That the
opposition between the terms now in question depends upon the
privation or presence of a certain state is clear, since animals
naturally possess each kind of 'sense', both as applied to the soul
and as applied to the body.
Moreover, examine the inflected forms. For if 'justly' has more than
one meaning, then 'just', also, will be used with more than one
meaning; for there will be a meaning of 'just' to each of the meanings
of 'justly'; e.g. if the word 'justly' be used of judging according to
one's own opinion, and also of judging as one ought, then 'just'
also will be used in like manner. In the same way also, if 'healthy'
has more than one meaning, then 'healthily' also will be used with
more than one meaning: e.g. if 'healthy' describes both what
produces health and what preserves health and what betokens health,
then 'healthily' also will be used to mean 'in such a way as to
produce' or 'preserve' or 'betoken' health. Likewise also in other
cases, whenever the original term bears more than one meaning, the
inflexion also that is formed from it will be used with more than
one meaning, and vice versa.
Look also at the classes of the predicates signified by the term,
and see if they are the same in all cases. For if they are not the
same, then clearly the term is ambiguous: e.g. 'good' in the case of
food means 'productive of pleasure', and in the case of medicine
> 'productive of health', whereas as applied to the soul it means to
be of a certain quality, e.g. temperate or courageous or just: and
likewise also, as applied to 'man'. Sometimes it signifies what
happens at a certain time, as (e.g.) the good that happens at the
right time: for what happens at the right time is called good. Often
it signifies what is of certain quantity, e.g. as applied to the
proper amount: for the proper amount too is called good. So then the
term 'good' is ambiguous. In the same way also 'clear', as applied
to a body, signifies a colour, but in regard to a note it denotes what
is 'easy to hear'. 'Sharp', too, is in a closely similar case: for the
same term does not bear the same meaning in all its applications:
for a sharp note is a swift note, as the mathematical theorists of
harmony tell us, whereas a sharp (acute) angle is one that is less
than a right angle, while a sharp dagger is one containing a sharp
angle (point).
Look also at the genera of the objects denoted by the same term, and
see if they are different without being subaltern, as (e.g.) 'donkey',
which denotes both the animal and the engine. For the definition of
them that corresponds to the name is different: for the one will be
declared to be an animal of a certain kind, and the other to be an
engine of a certain kind. If, however, the genera be subaltern,
there is no necessity for the definitions to be different. Thus (e.g.)
'animal' is the genus of 'raven', and so is 'bird'. Whenever therefore
we say that the raven is a bird, we also say that it is a certain kind
of animal, so that both the genera are predicated of it. Likewise also
whenever we call the raven a 'flying biped animal', we declare it to
be a bird: in this way, then, as well, both the genera are
predicated of raven, and also their definition. But in the case of
genera that are not subaltern this does not happen, for whenever we
call a thing an 'engine', we do not call it an animal, nor vice versa.
Look also and see not only if the genera of the term before you
are different without being subaltern, but also in the case of its
contrary: for if its contrary bears several senses, clearly the term
before you does so as well.
It is useful also to look at the definition that arises from the use
of the term in combination, e.g. of a 'clear (lit. white) body' of a
'clear note'. For then if what is peculiar in each case be abstracted,
the same expression ought to remain over. This does not happen in
the case of ambiguous terms, e.g. in the cases just mentioned. For the
former will be body possessing such and such a colour', while the
latter will be 'a note easy to hear'. Abstract, then, 'a body 'and'
a note', and the remainder in each case is not the same. It should,
however, have been had the meaning of 'clear' in each case been
synonymous.
Often in the actual definitions as well ambiguity creeps in
unawares, and for this reason the definitions also should be examined.
If (e.g.) any one describes what betokens and what produces health
as 'related commensurably to health', we must not desist but go on
to examine in what sense he has used the term 'commensurably' in
each case, e.g. if in the latter case it means that 'it is of the
right amount to produce health', whereas in the for it means that
'it is such as to betoken what kind of state prevails'.
Moreover, see if the terms cannot be compared as 'more or less' or
as 'in like manner', as is the case (e.g.) with a 'clear' (lit. white)
sound and a 'clear' garment, and a 'sharp' flavour and a 'sharp' note.
For neither are these things said to be clear or sharp 'in a like
degree', nor yet is the one said to be clearer or sharper than the
other. 'Clear', then, and 'sharp' are ambiguous. For synonyms are
always comparable; for they will always be used either in like manner,
or else in a greater degree in one case.
Now since of genera that are different without being subaltern the
differentiae also are different in kind, e.g. those of 'animal' and
'knowledge' (for the differentiae of these are different), look and
see if the meanings comprised under the same term are differentiae
of genera that are different without being subaltern, as e.g.
'sharp' is of a 'note' and a 'solid'. For being 'sharp' differentiates
note from note, and likewise also one solid from another. 'Sharp',
then, is an ambiguous term: for it forms differentiae of genera that
are different without being subaltern.
Again, see if the actual meanings included under the same term
themselves have different differentiae, e.g. 'colour' in bodies and
'colour' in tunes: for the differentiae of 'colour' in bodies are
'sight-piercing' and 'sight compressing', whereas 'colour' in melodies
has not the same differentiae. Colour, then, is an ambiguous term; for
things that are the same have the same differentiae.
Moreover, since the species is never the differentia of anything,
look and see if one of the meanings included under the same term be
a species and another a differentia, as (e.g.) clear' (lit. white)
as applied to a body is a species of colour, whereas in the case of
a note it is a differentia; for one note is differentiated from
another by being 'clear'.
16
The presence, then, of a number of meanings in a term may be
investigated by these and like means. The differences which things
present to each other should be examined within the same genera,
e.g. 'Wherein does justice differ from courage, and wisdom from
temperance?'-for all these belong to the same genus; and also from one
genus to another, provided they be not very much too far apart, e.g.
'Wherein does sensation differ from knowledge?: for in the case of
genera that are very far apart, the differences are entirely obvious.
17
Likeness should be studied, first, in the case of things belonging
to different genera, the formulae being 'A:B = C:D' (e.g. as knowledge
stands to the object of knowledge, so is sensation related to the
object of sensation), and 'As A is in B, so is C in D' (e.g. as
sight is in the eye, so is reason in the soul, and as is a calm in the
sea, so is windlessness in the air). Practice is more especially
needed in regard to terms that are far apart; for in the case of the
rest, we shall be more easily able to see in one glance the points
of likeness. We should also look at things which belong to the same
genus, to see if any identical attribute belongs to them all, e.g.
to a man and a horse and a dog; for in so far as they have any
identical attribute, in so far they are alike.
18
It is useful to have examined the number of meanings of a term
both for clearness' sake (for a man is more likely to know what it
is he asserts, if it bas been made clear to him how many meanings it
may have), and also with a view to ensuring that our reasonings
shall be in accordance with the actual facts and not addressed
merely to the term used. For as long as it is not clear in how m
any
senses a term is used, it is possible that the answerer and the
questioner are not directing their minds upon the same thing:
whereas when once it has been made clear how many meanings there
are, and also upon which of them the former directs his mind when he
makes his assertion, the questioner would then look ridiculous if he
failed to address his argument to this. It helps us also both to avoid
being misled and to mislead by false reasoning: for if we know the
number of meanings of a term, we shall certainly never be misled by
false reasoning, but shall know if the questioner fails to address his
argument to the same point; and when we ourselves put the questions we
shall be able to mislead him, if our answerer happens not to know
the number of meanings of our terms. This, however, is not possible in
all cases, but only when of the many senses some are true and others
are false. This manner of argument, however, does not belong
properly to dialectic; dialecticians should therefore by all means
beware of this kind of verbal discussion, unless any one is absolutely
unable to discuss the subject before him in any other way.
The discovery of the differences of things helps us both in
reasonings about sameness and difference, and also in recognizing what
any particular thing is. That it helps us in reasoning about
sameness and difference is clear: for when we have discovered a
difference of any kind whatever between the objects before us, we
shall already have shown that they are not the same: while it helps us
in recognizing what a thing is, because we usually distinguish the
expression that is proper to the essence of each particular thing by
means of the differentiae that are proper to it.
The examination of likeness is useful with a view both to
inductive arguments and to hypothetical reasonings, and also with a
view to the rendering of definitions. It is useful for inductive
arguments, because it is by means of an induction of individuals in
cases that are alike that we claim to bring the universal in evidence: