This is an exhaustive enumeration of all the pairs of opposite propositions that can possibly be framed. This last group should remain distinct from those which preceded it, since it employs as its subject the expression ‘not-man’.
When the verb ‘is’ does not fit the structure of the sentence (for instance, when the verbs ‘walks’, ‘enjoys health’ are used), that scheme applies, which applied when the word ‘is’ was added.
Thus we have the propositions: ‘every man enjoys health’, ‘every man does-not-enjoy-health’, ‘all that is not-man enjoys health’, ‘all that is not-man does-not-enjoy-health’. We must not in these propositions use the expression ‘not every man’. The negative must be attached to the word ‘man’, for the word ‘every’ does not give to the subject a universal significance, but implies that, as a subject, it is distributed. This is plain from the following pairs: ‘man enjoys health’, ‘man does not enjoy health’; ‘not-man enjoys health’, ‘not man does not enjoy health’. These propositions differ from the former in being indefinite and not universal in character. Thus the adjectives ‘every’ and no additional significance except that the subject, whether in a positive or in a negative sentence, is distributed. The rest of the sentence, therefore, will in each case be the same.
Since the contrary of the proposition ‘every animal is just’ is ‘no animal is just’, it is plain that these two propositions will never both be true at the same time or with reference to the same subject. Sometimes, however, the contradictories of these contraries will both be true, as in the instance before us: the propositions ‘not every animal is just’ and ‘some animals are just’ are both true.
Further, the proposition ‘no man is just’ follows from the proposition ‘every man is not just’ and the proposition ‘not every man is not just’, which is the opposite of ‘every man is not-just’, follows from the proposition ‘some men are just’; for if this be true, there must be some just men.
It is evident, also, that when the subject is individual, if a question is asked and the negative answer is the true one, a certain positive proposition is also true. Thus, if the question were asked Socrates wise?’ and the negative answer were the true one, the positive inference ‘Then Socrates is unwise’ is correct. But no such inference is correct in the case of universals, but rather a negative proposition. For instance, if to the question ‘Is every man wise?’ the answer is ‘no’, the inference ‘Then every man is unwise’ is false. But under these circumstances the inference ‘Not every man is wise’ is correct. This last is the contradictory, the former the contrary. Negative expressions, which consist of an indefinite noun or predicate, such as ‘not-man’ or ‘not-just’, may seem to be denials containing neither noun nor verb in the proper sense of the words. But they are not. For a denial must always be either true or false, and he that uses the expression ‘not man’, if nothing more be added, is not nearer but rather further from making a true or a false statement than he who uses the expression ‘man’.
The propositions ‘everything that is not man is just’, and the contradictory of this, are not equivalent to any of the other propositions; on the other hand, the proposition ‘everything that is not man is not just’ is equivalent to the proposition ‘nothing that is not man is just’.
The conversion of the position of subject and predicate in a sentence involves no difference in its meaning. Thus we say ‘man is white’ and ‘white is man’. If these were not equivalent, there would be more than one contradictory to the same proposition, whereas it has been demonstrated’ that each proposition has one proper contradictory and one only. For of the proposition ‘man is white’ the appropriate contradictory is ‘man is not white’, and of the proposition ‘white is man’, if its meaning be different, the contradictory will either be ‘white is not not-man’ or ‘white is not man’. Now the former of these is the contradictory of the proposition ‘white is not-man’, and the latter of these is the contradictory of the proposition ‘man is white’; thus there will be two contradictories to one proposition.
It is evident, therefore, that the inversion of the relative position of subject and predicate does not affect the sense of affirmations and denials.
11
There is no unity about an affirmation or denial which, either positively or negatively, predicates one thing of many subjects, or many things of the same subject, unless that which is indicated by the many is really some one thing. do not apply this word ‘one’ to those things which, though they have a single recognized name, yet do not combine to form a unity. Thus, man may be an animal, and biped, and domesticated, but these three predicates combine to form a unity. On the other hand, the predicates ‘white’, ‘man’, and ‘walking’ do not thus combine. Neither, therefore, if these three form the subject of an affirmation, nor if they form its predicate, is there any unity about that affirmation. In both cases the unity is linguistic, but not real.
If therefore the dialectical question is a request for an answer, i.e. either for the admission of a premiss or for the admission of one of two contradictories-and the premiss is itself always one of two contradictories-the answer to such a question as contains the above predicates cannot be a single proposition. For as I have explained in the Topics, question is not a single one, even if the answer asked for is true.
At the same time it is plain that a question of the form ‘what is it?’ is not a dialectical question, for a dialectical questioner must by the form of his question give his opponent the chance of announcing one of two alternatives, whichever he wishes. He must therefore put the question into a more definite form, and inquire, e.g.. whether man has such and such a characteristic or not.
Some combinations of predicates are such that the separate predicates unite to form a single predicate. Let us consider under what conditions this is and is not possible. We may either state in two separate propositions that man is an animal and that man is a biped, or we may combine the two, and state that man is an animal with two feet. Similarly we may use ‘man’ and ‘white’ as separate predicates, or unite them into one. Yet if a man is a shoemaker and is also good, we cannot construct a composite proposition and say that he is a good shoemaker. For if, whenever two separate predicates truly belong to a subject, it follows that the predicate resulting from their combination also truly belongs to the subject, many absurd results ensue. For instance, a man is man and white. Therefore, if predicates may always be combined, he is a white man. Again, if the predicate ‘white’ belongs to him, then the combination of that predicate with the former composite predicate will be permissible. Thus it will be right to say that he is a white man so on indefinitely. Or, again, we may combine the predicates ‘musical’, ‘white’, and ‘walking’, and these may be combined many times. Similarly we may say that Socrates is Socrates and a man, and that therefore he is the man Socrates, or that Socrates is a man and a biped, and that therefore he is a two-footed man. Thus it is manifest that if man states unconditionally that predicates can always be combined, many absurd consequences ensue.
We will now explain what ought to be laid down.
Those predicates, and terms forming the subject of predication, which are accidental either to the same subject or to one another, do not combine to form a unity. Take the proposition ‘man is white of complexion and musical’. Whiteness and being musical do not coalesce to form a unity, for they belong only accidentally to the same subject. Nor yet, if it were true to say that that which is white is musical, would the terms ‘musical’ and ‘white’ form a unity, for it is only incidentally that that which is musical is white; the combination of the two will, therefore, not form a unity.
Thus, again, whereas, if a man is both good and a shoemaker, we cannot combine the two propositions and say simply that he is a good shoemaker, we are, at the same time, able to combine the predicates ‘animal’ and ‘biped’ and say that a man is an animal with two feet, for these predicates are not accidental.
Those predicates, again, cannot form a unity, of which the one is implicit in the other: