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Aristotle

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cases that are alike that we claim to bring the universal in evidence:

  for it is not easy to do this if we do not know the points of

  likeness. It is useful for hypothetical reasonings because it is a

  general opinion that among similars what is true of one is true also

  of the rest. If, then, with regard to any of them we are well supplied

  with matter for a discussion, we shall secure a preliminary

  admission that however it is in these cases, so it is also in the case

  before us: then when we have shown the former we shall have shown,

  on the strength of the hypothesis, the matter before us as well: for

  we have first made the hypothesis that however it is in these cases,

  so it is also in the case before us, and have then proved the point as

  regards these cases. It is useful for the rendering of definitions

  because, if we are able to see in one glance what is the same in

  each individual case of it, we shall be at no loss into what genus

  we ought to put the object before us when we define it: for of the

  common predicates that which is most definitely in the category of

  essence is likely to be the genus. Likewise, also, in the case of

  objects widely divergent, the examination of likeness is useful for

  purposes of definition, e.g. the sameness of a calm at sea, and

  windlessness in the air (each being a form of rest), and of a point on

  a line and the unit in number-each being a starting point. If, then,

  we render as the genus what is common to all the cases, we shall get

  the credit of defining not inappropriately. Definition-mongers too

  nearly always render them in this way: they declare the unit to be the

  startingpoint of number, and the point the startingpoint of a line. It

  is clear, then, that they place them in that which is common to both

  as their genus.

  The means, then, whereby reasonings are effected, are these: the

  commonplace rules, for the observance of which the aforesaid means are

  useful, are as follows.

  Book II

  1

  Of problems some are universal, others particular. Universal

  problems are such as 'Every pleasure is good' and 'No pleasure is

  good'; particular problems are such as 'Some pleasure is good' and

  'Some pleasure is not good'. The methods of establishing and

  overthrowing a view universally are common to both kinds of

  problems; for when we have shown that a predicate belongs in every

  case, we shall also have shown that it belongs in some cases.

  Likewise, also, if we show that it does not belong in any case, we

  shall also have shown that it does not belong in every case. First,

  then, we must speak of the methods of overthrowing a view universally,

  because such are common to both universal and particular problems, and

  because people more usually introduce theses asserting a predicate

  than denying it, while those who argue with them overthrow it. The

  conversion of an appropriate name which is drawn from the element

  'accident' is an extremely precarious thing; for in the case of

  accidents and in no other it is possible for something to be true

  conditionally and not universally. Names drawn from the elements

  'definition' and 'property' and 'genus' are bound to be convertible;

  e.g. if 'to be an animal that walks on two feet is an attribute of S',

  then it will be true by conversion to say that 'S is an animal that

  walks on two feet'. Likewise, also, if drawn from the genus; for if

  'to be an animal is an attribute of S', then 'S is an animal'. The

  same is true also in the case of a property; for if 'to be capable

  of learning grammar is an attribute of S', then 'S will be capable

  of learning grammar'. For none of these attributes can possibly belong

  or not belong in part; they must either belong or not belong

  absolutely. In the case of accidents, on the other hand, there is

  nothing to prevent an attribute (e.g. whiteness or justice)

  belonging in part, so that it is not enough to show that whiteness

  or justice is an attribute of a man in order to show that he is

  white or just; for it is open to dispute it and say that he is white

  or just in part only. Conversion, then, is not a necessary process

  in the case of accidents.

  We must also define the errors that occur in problems. They are of

  two kinds, caused either by false statement or by transgression of the

  established diction. For those who make false statements, and say that

  an attribute belongs to thing which does not belong to it, commit

  error; and those who call objects by the names of other objects

  (e.g. calling a planetree a 'man') transgress the established

  terminology.

  2

  Now one commonplace rule is to look and see if a man has ascribed as

  an accident what belongs in some other way. This mistake is most

  commonly made in regard to the genera of things, e.g. if one were to

  say that white happens (accidit) to be a colour-for being a colour

  does not happen by accident to white, but colour is its genus. The

  assertor may of course define it so in so many words, saying (e.g.)

  that 'Justice happens (accidit) to be a virtue'; but often even

  without such definition it is obvious that he has rendered the genus

  as an accident; e.g. suppose that one were to say that whiteness is

  coloured or that walking is in motion. For a predicate drawn from

  the genus is never ascribed to the species in an inflected form, but

  always the genera are predicated of their species literally; for the

  species take on both the name and the definition of their genera. A

  man therefore who says that white is 'coloured' has not rendered

  'coloured' as its genus, seeing that he has used an inflected form,

  nor yet as its property or as its definition: for the definition and

  property of a thing belong to it and to nothing else, whereas many

  things besides white are coloured, e.g. a log, a stone, a man, and a

  horse. Clearly then he renders it as an accident.

  Another rule is to examine all cases where a predicate has been

  either asserted or denied universally to belong to something. Look

  at them species by species, and not in their infinite multitude: for

  then the inquiry will proceed more directly and in fewer steps. You

  should look and begin with the most primary groups, and then proceed

  in order down to those that are not further divisible: e.g. if a man

  has said that the knowledge of opposites is the same, you should

  look and see whether it be so of relative opposites and of

  contraries and of terms signifying the privation or presence of

  certain states, and of contradictory terms. Then, if no clear result

  be reached so far in these cases, you should again divide these

  until you come to those that are not further divisible, and see (e.g.)

  whether it be so of just deeds and unjust, or of the double and the

  half, or of blindness and sight, or of being and not-being: for if

  in any case it be shown that the knowledge of them is not the same

  we shall have demolished the problem. Likewise, also, if the predicate

  belongs in no case. This rule is convertible for both destructive

  and constructiv
e purposes: for if, when we have suggested a

  division, the predicate appears to hold in all or in a large number of

  cases, we may then claim that the other should actually assert it

  universally, or else bring a negative instance to show in what case it

  is not so: for if he does neither of these things, a refusal to assert

  it will make him look absurd.

  Another rule is to make definitions both of an accident and of its

  subject, either of both separately or else of one of them, and then

  look and see if anything untrue has been assumed as true in the

  definitions. Thus (e.g.) to see if it is possible to wrong a god,

  ask what is 'to wrong'? For if it be 'to injure deliberately', clearly

  it is not possible for a god to be wronged: for it is impossible

  that God should be injured. Again, to see if the good man is

  jealous, ask who is the 'jealous' man and what is 'jealousy'. For if

  'jealousy' is pain at the apparent success of some well-behaved

  person, clearly the good man is not jealous: for then he would be bad.

  Again, to see if the indignant man is jealous, ask who each of them

  is: for then it will be obvious whether the statement is true or

  false; e.g. if he is 'jealous' who grieves at the successes of the

  good, and he is 'indignant' who grieves at the successes of the

  evil, then clearly the indignant man would not be jealous. A man

  should substitute definitions also for the terms contained in his

  definitions, and not stop until he comes to a familiar term: for often

  if the definition be rendered whole, the point at issue is not cleared

  up, whereas if for one of the terms used in the definition a

  definition be stated, it becomes obvious.

  Moreover, a man should make the problem into a proposition for

  himself, and then bring a negative instance against it: for the

  negative instance will be a ground of attack upon the assertion.

  This rule is very nearly the same as the rule to look into cases where

  a predicate has been attributed or denied universally: but it

  differs in the turn of the argument.

  Moreover, you should define what kind of things should be called

  as most men call them, and what should not. For this is useful both

  for establishing and for overthrowing a view: e.g. you should say that

  we ought to use our terms to mean the same things as most people

  mean by them, but when we ask what kind of things are or are not of

  such and such a kind, we should not here go with the multitude: e.g.

  it is right to call 'healthy' whatever tends to produce health, as

  do most men: but in saying whether the object before us tends to

  produce health or not, we should adopt the language no longer of the

  multitude but of the doctor.

  3

  Moreover, if a term be used in several senses, and it has been

  laid down that it is or that it is not an attribute of S, you should

  show your case of one of its several senses, if you cannot show it

  of both. This rule is to be observed in cases where the difference

  of meaning is undetected; for supposing this to be obvious, then the

  other man will object that the point which he himself questioned has

  not been discussed, but only the other point. This commonplace rule is

  convertible for purposes both of establishing and of overthrowing a

  view. For if we want to establish a statement, we shall show that in

  one sense the attribute belongs, if we cannot show it of both

  senses: whereas if we are overthrowing a statement, we shall show that

  in one sense the attribute does not belong, if we cannot show it of

  both senses. Of course, in overthrowing a statement there is no need

  to start the discussion by securing any admission, either when the

  statement asserts or when it denies the attribute universally: for

  if we show that in any case whatever the attribute does not belong, we

  shall have demolished the universal assertion of it, and likewise also

  if we show that it belongs in a single case, we shall demolish the

  universal denial of it. Whereas in establishing a statement we ought

  to secure a preliminary admission that if it belongs in any case

  whatever, it belongs universally, supposing this claim to be a

  plausible one. For it is not enough to discuss a single instance in

  order to show that an attribute belongs universally; e.g. to argue

  that if the soul of man be immortal, then every soul is immortal, so

  that a previous admission must be secured that if any soul whatever be

  immortal, then every soul is immortal. This is not to be done in every

  case, but only whenever we are not easily able to quote any single

  argument applying to all cases in common, as (e.g.) the geometrician

  can argue that the triangle has its angles equal to two right angles.

  If, again, the variety of meanings of a term be obvious, distinguish

  how many meanings it has before proceeding either to demolish or to

  establish it: e.g. supposing 'the right' to mean 'the expedient' or

  'the honourable', you should try either to establish or to demolish

  both descriptions of the subject in question; e.g. by showing that

  it is honourable and expedient, or that it is neither honourable nor

  expedient. Supposing, however, that it is impossible to show both, you

  should show the one, adding an indication that it is true in the one

  sense and not in the other. The same rule applies also when the number

  of senses into which it is divided is more than two.

  Again, consider those expressions whose meanings are many, but

  differ not by way of ambiguity of a term, but in some other way:

  e.g. 'The science of many things is one': here 'many things' may

  mean the end and the means to that end, as (e.g.) medicine is the

  science both of producing health and of dieting; or they may be both

  of them ends, as the science of contraries is said to be the same (for

  of contraries the one is no more an end than the other); or again they

  may be an essential and an accidental attribute, as (e.g.) the

  essential fact that the triangle has its angles equal to two right

  angles, and the accidental fact that the equilateral figure has them

  so: for it is because of the accident of the equilateral triangle

  happening to be a triangle that we know that it has its angles equal

  to two right angles. If, then, it is not possible in any sense of

  the term that the science of many things should be the same, it

  clearly is altogether impossible that it should be so; or, if it is

  possible in some sense, then clearly it is possible. Distinguish as

  many meanings as are required: e.g. if we want to establish a view, we

  should bring forward all such meanings as admit that view and should

  divide them only into those meanings which also are required for the

  establishment of our case: whereas if we want to overthrow a view,

  we should bring forward all that do not admit that view, and leave the

  rest aside. We must deal also in these cases as well with any

  uncertainty about the number of meanings involved. Further, that one

  thing is, or is not, 'of' another should be established by means of

  the same commonplace rules; e.g. that a particular science is o
f a

  particular thing, treated either as an end or as a means to its end,

  or as accidentally connected with it; or again that it is not 'of'

  it in any of the aforesaid ways. The same rule holds true also of

  desire and all other terms that have more than one object. For the

  'desire of X' may mean the desire of it as an end (e.g. the desire

  of health) or as a means to an end (e.g. the desire of being

  doctored), or as a thing desired accidentally, as, in the case of

  wine, the sweet-toothed person desires it not because it is wine but

  because it is sweet. For essentially he desires the sweet, and only

  accidentally the wine: for if it be dry, he no longer desires it.

  His desire for it is therefore accidental. This rule is useful in

  dealing with relative terms: for cases of this kind are generally

  cases of relative terms.

  4

  Moreover, it is well to alter a term into one more familiar, e.g. to

  substitute 'clear' for 'exact' in describing a conception, and

  'being fussy' for 'being busy': for when the expression is made more

  familiar, the thesis becomes easier to attack. This commonplace rule

  also is available for both purposes alike, both for establishing and

  for overthrowing a view.

  In order to show that contrary attributes belong to the same

  thing, look at its genus; e.g. if we want to show that rightness and

  wrongness are possible in regard to perception, and to perceive is

  to judge, while it is possible to judge rightly or wrongly, then in

  regard to perception as well rightness and wrongness must be possible.

  In the present instance the proof proceeds from the genus and

  relates to the species: for 'to judge' is the genus of 'to -perceive';

  for the man who perceives judges in a certain way. But per contra it

  may proceed from the species to the genus: for all the attributes that

  belong to the species belong to the genus as well; e.g. if there is

  a bad and a good knowledge there is also a bad and a good disposition:

  for 'disposition' is the genus of knowledge. Now the former

  commonplace argument is fallacious for purposes of establishing a

 

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