Tractate III. Chapters XV-XX

is commonly said of every consequent of this sort, and that from which the consequence is not converted. On account of this, in every fallacy of the consequent there are necessarily two consequences: one, indeed, of the consequent to the antecedent, and the other the converse of that, namely of the antecedent to the consequent, which is sometimes true and sometimes fails. And because the defect always occurs in that one, therefore this fallacy is called of the consequent and not of the antecedent. For if the consequence is simple, it does not fail in the antecedent by inferring the consequent, but it fails in the consequent from which the antecedent is believed to be inferred. As: if man exists, animal exists; this consequence does not fail, but its converse fails, if it is inferred, therefore if animal exists, man exists. But if the consequence is composite from the contrary, then the antecedent is made the consequent, and then again that which was the antecedent fails, but through negation it has been made the consequent. As if it is said: if man exists, animal exists; therefore if non-man exists, non-animal exists. For there one proceeds from destruction of the antecedent, which through negation has been made the consequent; and therefore this fallacy chiefly occurs when one proceeds either from destruction of the antecedent or from position of the consequent. For the less common is not inferred from the more common, since it is in it only in potency and not in act; but the more common is inferred from the less common, because it is in it in act.

But if someone says that even from an equal something is inferred, and conversely, one must say that this is true; but that consequence is good and does not introduce a fallacy. Hence it is clear why this fallacy is called the fallacy of the consequent and not of the antecedent. But the cause of appearance in this fallacy is the identity of the antecedent with the consequent, which is in it either necessarily or probably or suspicably; from this it is believed that, just as the consequent is inferred from the antecedent, so conversely the consequent infers the antecedent. But the cause of defect or of non-existence is the diversity of the consequent from the antecedent, in which the antecedent is not, except in potency; and therefore it cannot be inferred from it.

CHAPTER XVI. On the fallacy of the consequent and its modes.

With these things thus prefaced concerning the fallacy according to the consequent, we say that that apparent refutation which is according to the consequent generally, as to the cause of appearance, occurs because respondents think that the consequence of consequent to antecedent, which is a true consequence, is converted into that which is of antecedent to consequent. This frequently fails; for since this antecedent, namely the true (which infers a consequent from the necessity of consequence of position or of thing), is that which is consequent to it, therefore when that exists, namely the consequent, the respondents themselves think that the other thing, which is the antecedent, exists from the necessity of the consequence of antecedent to consequent; and this is not necessary. For it is not generally true that, if when the antecedent is posited the consequent is posited, also conversely, when the consequent is posited, the antecedent is posited. Hence from this also the cause is taken, that from sense, that is, from sensible common accidents not proper, accepted through sense, fallacies are made, or deceptions are made concerning the opinion composing an accident about a subject.

For such people have often suspected or opined that honey is gall, by accepting things common to honey and gall, judging that just as a common accident or predicate follows upon a subject, so conversely the subject follows upon a common predicate. For if it is honey, it is red, that is, something red. And they thought the converse to follow: if it is red, it is honey. But they inferred: but gall is red; therefore gall is honey. This deception is made because red color and a common predicate follow honey as antecedent and subject. And the paralogism is formed thus: if it is honey, it is red; but this, with gall pointed out, is red just as honey is; therefore gall is honey.

And this is in natural things in the same way; because, since by a general consequence it happens that through rain the earth becomes wet, they think conversely that if the earth is wet, it has rained; and this is not necessary, because it can be wet from another cause. Hence the consequent does not infer the antecedent of necessity. And the paralogism can be formed thus: if the earth is wet, it has been rained upon; but the earth soaked with water is wet; therefore it has been rained upon. For in each of these paralogisms there is the fallacy of the consequent from position of the consequent, and each of these is made in a consequence of necessary matter.

Similarly, however, in matter in which the converted consequence is not necessary, but only probable or suspicable, as in rhetorical demonstrations, that is, proofs or showings, which are according to common and not proper signs. For they are made from adjunct predicates to some subject, which by Tullius are called common accidents. For rhetoricians themselves, wishing to show or prove that someone is an adulterer, take that common predicate which is commonly joined to an adulterer, or is commonly accidental to an adulterer, as that he is composed, ornamented, and groomed, and often looks toward the wife of another; or that he is seen wandering at night. From this suspicion is generated that he is an adulterer and a thief. But these common accidents are in or happen to more subjects than to the adulterer alone, and in them the predicate of the converted consequence, which is being an adulterer, is not present; and therefore this predicate is not inferred of necessity from that. And the paralogism can be formed thus: if someone is an adulterer, he is groomed and polished; but this man is groomed and polished; therefore he is an adulterer. Or thus: if someone is a thief, this man is wandering at night; but this man is wandering at night; therefore he is a thief. One must know that in such things, as Boethius says, the place from adjuncts or common accidents, when the adjuncts are taken as proper, because those are signs and probabilities, concludes in the first figure, as here: whatever has milk in the breasts without rubbing of the breasts with salt and nettle has given birth; this one thus has milk in the breasts; therefore she has given birth. But I say without rubbing of the breasts because Aristotle says that if the breasts of a virgin, or even of a man having large breasts, are rubbed with salt or nettle, he or she will have milk in the breasts, but it will be thin and little and not sufficient for nursing. But if there are signs and adjuncts in the second figure which are common predicates, such as being pale, and adjunct to those who have given birth, as Aristotle says at the end of the second book of the Prior Analytics, and only one such accident or adjunct is taken, then the predicate will be more common than what could infer the subject, and then there will be the fallacy of the consequent. And therefore if there ought to be a place from common accidents, then such an adjunct must be taken with circumstances of the person, because when it is taken with many such things, it will be proper and will infer the subject, which only one adjunct will not be able to infer. For in these things what Aristotle says about defining parts and definition is true, namely that the parts are in more, and the whole is in equal; and thus one argues in rhetoricals and in physiognomics and in other demonstrative sciences, as in astronomy and in others in which demonstration is made from signs.

One must also know that such consequences are not necessary according to the necessity of antecedent and consequent, although they are sufficiently necessary for making an estimation for judgment or suspicion; and this is here called the necessity of consequence, because, as Boethius says while speaking generally of every argument, an argument is an account making faith concerning a doubtful thing, calling any credulity faith.

Similarly, however, another mode of this fallacy is also in syllogistic things, which are simply syllogistic and are concluded syllogistically, as the reasoning of Melissus has itself, by which he proves that the world is ungenerated and infinite in duration, or by which he proves the universe itself or world to be called infinite, taking as proof that the universe is unbegotten, that is, not generated, and consequently eternal, or infinite according to duration. For he does not posit creation, because he posits that nothing is made from nothing, but whatever things are made, he posits to be made through generation from a material principle; for everything that has been made, he posits to have been made from a material principle, which it needs in order that it be something. And he argues thus: if something has been made, it has a principle; the universe or world has not been made; therefore it does not have a principle. And the paralogism can be formed thus: everything that has been made has a principle; the world has not been made; therefore it does not have a principle. And it is from destruction of the antecedent, and this is not to happen of necessity; for it is not necessary according to consequence that, if everything that has been made has a material principle, also conversely whatever has a material principle itself has been made. And an instance of this consequence is as if fever is in one fevering, heat is; and nevertheless it is not necessary that, if someone is hot, he is fevering or has a fever.

Yet this seems not to be to the point; for since according to the reasoning of Melissus it ought to be shown that this consequence is not valid, the world has not been made, therefore it does not have a principle, this one is manifested as not valid: the world has a principle, therefore it has been made. But there is a twofold reason for this, namely that the sin of Melissus's consequence is not manifested in itself, but in the consequence which precedes Melissus's consequence. One is this: because the goodness is the same and the sin is the same of any consequence or argument and of its converse; and so that this may be shown, the badness of Melissus's consequence is manifested in its converse. But the second reason is that this is done so that it may be intimated that the same mode is in substance when arguing from position of the consequent and from destruction of the antecedent.

From the things which have been said, it is clear that there are three modes of the fallacy of the consequent. The first mode is when a consequence made according to local relations is converted. As: if it is man, it is animal; therefore if it is animal, it is man. And it is from position of the consequent. Similarly also here: if it is not animal, it is not man; therefore if it is not man, it is not animal; for this consequence also is from position of the consequent. Similarly also here: if it is honey, it is red; therefore if it is red, it is honey; but gall is red; therefore gall is honey. Similarly here: if it rains, the earth is wet; therefore if the earth is wet, it rains. For in all these it is thought that a consequence is converted which is not converted, and therefore the sin according to the consequent occurs.

The second mode is when a consequence is thought to be converted because of adjuncts or circumstances inhering in something through itself; and this especially occurs in rhetoricals. As: if he is an adulterer, he is groomed. Or if he is a thief, he wanders at night. Therefore if he is groomed, he is an adulterer. Or if he wanders at night, he is a thief. For this is the fallacy of the consequent, because this consequence is good: if he is an adulterer, he is groomed, because an adulterer has some one of the circumstances of adulterers; but it does not follow conversely, because it is not necessary, if he has some one of the circumstances of an adulterer, that he is an adulterer; just as it follows well, if he is a man, he is colored, but it does not follow conversely, if he is colored, that he is a man. Similarly here: if someone has stolen something, he has not gained it nor borrowed it; therefore if he has not gained it nor borrowed it, he has stolen it.

The third mode is when someone thinks that a consequence made according to oppositions is converted, as in the argumentation of Melissus: as if it has been made, it has the principle of its duration, and it is understood of what is made through generation or through a making of art; therefore if it has not been made through generation or art, it does not have a principle. But the world has not been made; therefore the world does not have a principle; therefore the world is infinite in duration, that is, from eternity. For Melissus sinned according to the consequent in the first inference; for this consequence is right: if it has been made, it has a principle, because everything generated by nature or art has a material principle, because nothing comes from nothing. But it does not follow, if it has not been made, it does not have a principle, because an argument is made from destruction of the antecedent, and it places a consequence in itself among contradictorily opposed things, whereas in such things a consequence from the contrary must always be posited. As: if it has been made, it has a principle; therefore if it does not have a principle, it has not been made. This is a good consequence.

And from the foregoing it is clear what was said a little before, that wherever there is a consequent, there is always a double consequence, because of the substance of any paralogism there is a moving principle and a principle of defect in all fallacies, both in diction and outside diction. Therefore, since in the fallacy of the consequent the direct consequence is the moving principle of its appearance, but the fallacy is the principle of defect or principle of non-existence, there must be a double consequence wherever the fallacy of the consequent is, namely that which is converted and that into which it is converted. Hence it is clear that in such arguments as: animal runs; therefore man runs; therefore Socrates runs, there is not a sophism of the consequent, but of the antecedent.

Nevertheless some say that there are two modes of paralogizing of this kind in the fallacy of the consequent; for this fallacy is made when we think a consequence to be converted which is not converted. But over the same terms it occurs only in three ways: either each consequence is necessary, or only one, or neither. If each is necessary, then there is no deception. But if one is necessary and the other is not, yet the respondent sees one consequence to be necessary and also believes its converse to be necessary, then he is deceived and this is the first mode of the consequent from position of the consequent. But if neither is necessary, then he takes one to be probable and believes on account of this that its converse is probable; then he is deceived, and the second mode is made, as also happens in rhetorical arguments; and thus there are two modes of the fallacy of the consequent.

And if it is asked why different modes are not made according to position of the consequent and destruction of the antecedent, they say that these two modes are one mode in substance, differing only in mode, as was said in the foregoing.

CHAPTER XVII. On the preliminaries for understanding the fallacy according to non-cause as cause.

But for understanding the things which must be said about the fallacy according to non-cause as cause, one must know that a syllogism is twofold, as was said in the Prior Analytics. For there is a certain ostensive syllogism, which has a single conclusion syllogized from two propositions and three terms, as: every man is animal; Socrates is a man; therefore Socrates is animal. But a syllogism to the impossible is one which ostensively and syllogistically reduces something concluded to some manifest impossible thing; and because of this one of the premises, whichever one is the cause of that impossible thing which has been concluded, is destroyed; and because of this that syllogism always has two conclusions. As if it is asked whether a man is an ass; and if it is granted that he is an ass, let the contrary be syllogized thus: no ass is a rational mortal animal; man is an ass; therefore man is not a rational mortal animal. But this is false; therefore man is not an ass. And thus this premise is destroyed: man is an ass. For this syllogism is in the fourth mode of the first figure. Hence one must know that the fallacy according to non-cause as cause always occurs in a syllogism to the impossible; for the fallacy according to non-cause as cause occurs when a non-cause is posited as a cause. On that account the impossible seems to follow, although it does not follow because of it, but even apart from it the same impossible nevertheless happens. An example of this is as if it is asked whether Brunellus, or some ass, is a man; and if it is granted that some ass is a man, it is argued to the contrary thus: no ass is a rational mortal animal; man is an ass; some ass is a man, or Brunellus is a man; therefore man is not a rational mortal animal. But this is impossible; therefore this also: Brunellus or some ass is not a man. For in such an argumentation there is non-cause as cause, because this is destroyed which seems to be the cause of that impossible which was following, and is not its cause, namely this: Brunellus or some ass is a man; for without it the impossible follows from the other things posited, and the syllogism will be in the fourth mode of the first figure, as was said.

But since according to Aristotle in the eighth book of the Topics, one speech is false because from it no conclusion at all follows, which according to him in the same place is an apparent syllogism; another speech is false in which some conclusion follows, but not to the proposed point, which happens in syllogisms to the impossible; and thus it seems that all modes of apparent syllogisms fall under the first mode of the figure of diction, and only the paralogisms of that fallacy which happen in syllogisms to the impossible fall under the second mode of the figure of diction. And thus it seems that the paralogisms of that fallacy are not apparent syllogisms, and consequently that non-cause as cause is not a fallacy, since it does not have a cause of appearance.

But to this it must be said that for certain non-cause as cause is a fallacy, and an apparent syllogism which is made according to it. For apparent syllogism is said in two ways, namely specially and generally. Specially, an apparent syllogism is said to be one which sins against the consequence of an ostensive syllogism; because in this way the first speech is called false in Topics VIII, and in this way false speech does not comprehend under itself apparent syllogisms, for it does not comprehend paralogisms according to begging the principle, nor also paralogisms of the fallacy according to non-cause as cause, because they sin against any consequence whatever or the consequence of any ostensive syllogism. But generally, an apparent syllogism is said to be one which sins against any consequence whatever or the consequence of any syllogism whatever; and in this way apparent syllogism comprehends under itself the paralogisms of all fallacies, both in diction and outside diction. For all sin against some consequence of some syllogism; and in this way the paralogisms of this place are apparent syllogisms. But this fallacy sins against the dialectical syllogism; for although the ostensive syllogism properly belongs to the use of the dialectician for concluding his proposed point from probabilities, since also the syllogism to the impossible is in a case of use to the dialectician, namely when from things said by the respondent he can conclude something manifestly false, against whose falsity the respondent cannot object, thus this fallacy sins against the dialectical syllogism in such a case, existing in the use of the dialectician.

Again it must be noted that the universal cause of deceiving in this fallacy, according to Aristotle, is when that which is not the cause of the consequence is assumed, as though on account of it, as on account of the cause of the consequence, the refutation is made. This cause of deception is in all sophistical places or fallacies. For in all of them the premises seem to be causes of the refutation, and nevertheless they are not causes.

But one must know that there are two ways to take non-cause as cause. In one way, such that when it has been removed and the others still remain, the conclusion follows; and thus in this fallacy it is called non-cause as cause. But in another way, non-cause is said generally, that from which a conclusion does not follow, although it seems to follow; and thus non-cause taken as cause of the conclusion is in all fallacies. For if it is argued thus: every dog is barkable; the sea-dog is a dog; therefore the sea-dog is barkable. Neither of those propositions is the cause of the conclusion; nevertheless, when one of them has been removed, the same conclusion still follows from the other remaining things.

One must know that this fallacy or this sophistical place cannot happen in ostensive syllogisms, nor does it sin against the ostensive syllogism, but only against a syllogism to the impossible, as Aristotle says in the second book of the Prior Analytics, because for the false to happen not on account of this, and for there to be non-cause as cause, are the same. But for understanding this, one must distinguish: because if a proposition which is not the cause of the conclusion is taken with the propositions which are causes of the same conclusion as to the inference of it, either that proposition will communicate with the premises which are causes in some term, or it will not communicate with them in any term. If it will not communicate with them in any term, then there will not be a fallacy and sophistical place, because the apparent thing was lacking; for although that proposition is a non-cause, nevertheless it is not a non-cause as cause, because it is with nothing that is a cause. And about such a thing it is said in the second book of the Prior Analytics that it is a more manifest mode of the syllogism happening not on account of this. The example of this, posited in the second book of the Prior Analytics, is that if this must be shown, the diameter is incommensurable with the side, and the opposite of this, given by the respondent by hypothesis, is taken by the opponent with the reasoning of Zeno thus: the diameter is commensurable with the side; in any stadium there are infinite spaces; but it is not possible to cross infinite things; therefore it is not possible to cross any stadium. But this is impossible; therefore the hypothesis from which it follows is impossible, namely this, that the diameter is commensurable with the side. For in this argumentation the hypothesis which is a non-cause does not communicate in any term with the propositions which are causes of the conclusion; and therefore there is no appearance here, nor any sophistical place.

But if the proposition assumed communicates with those things which are the cause of the conclusion in some term, through which communication it seems to be a cause, this can happen only in one of two ways: in one way, namely, that by those propositions it is intended that some false thing be concluded directly only, so that there is a stop there; or it is intended to proceed further and conclude, namely from the falsity of that conclusion to destroy some position or hypothesis made and previously granted by the respondent. If, indeed, in the first way it is intended by such propositions to conclude a false thing where one stops, this can happen in two ways: for either from the remaining propositions, after that false thing assumed, the conclusion follows by necessity of consequence, or it does not follow from them. If it does not follow from them, then this fallacy has not been made, but the cause why it does not follow from the remaining things is another fallacy, either in diction or outside diction. But if the conclusion follows by necessity of inference from the remaining things, then there will be no fallacy at all, because although it is a non-cause, nevertheless it is not a non-cause as cause. For in this fallacy the whole appearance consists with respect to that proposition which is a non-cause, which has been assumed for the consequence of the conclusion; and it is not so in such arguments. For the appearance in arguments of this kind is the necessity of consequence; but the non-existence is in the assumed proposition, and such an appearance and such a non-existence cause some special fallacy. But if in such a process a false conclusion is intended, and from the falsity of that it is intended that some hypothesis previously posited or granted be destroyed, then that fallacy which is called non-cause occurs. And then the sin of that fallacy happens not in the first argument, but in the second, namely when it proceeds from a false conclusion and it happens that the hypothesis is false, as is clear in the example which Aristotle gives and which is taken from Plato's Phaedrus, which will be set down by us in the following chapter. Hence, since the proposition which is the non-cause cannot have itself in more ways, and according to no mode can it be made except according to the last one, it is clear that non-cause as cause cannot be made except in syllogisms to the impossible, and it sins against the second argument and not against the first, and as to the second and not against the first.

But if someone objecting against this says that for something to happen not on account of that is the same as being a non-cause as cause, but happening not on account of this can occur in ostensive syllogisms; therefore non-cause can also occur in ostensive syllogisms; therefore also non-cause as cause can occur in ostensive syllogisms. But let him prove that happening not on account of something can occur in ostensive syllogisms thus: for something to happen which is a non-cause of the conclusion as if it were a cause happens in two ways, namely so that the proposition taken, which is the non-cause, communicates with the premises in some term, or not. An example of what does not communicate in any term is as if it is said: every man runs; Socrates is a man; therefore Socrates runs. But an example of what communicates in some term is as if it is said thus: every ass is animal; every man is animal; therefore every brayable thing is an ass or animal. Therefore it is manifest that in these ostensive syllogisms it happens that a proposition is a non-cause as cause, and as if it were a cause; and consequently in ostensive syllogisms it happens to accept a non-cause as cause and to incur this fallacy. If, I say, someone objects thus, one must say that it is true that in this process in the first argument a proposition is taken which is a non-cause; yet nevertheless this fallacy does not have to be demonstrated from this, on account of the cause which has already been stated before.

The cause of appearance in this fallacy is the agreement in some term of that proposition which is not a cause with the proposition which truly has itself as necessary for the inference of the conclusion. For because of that agreement it is thought that the non-cause is the cause of the inference. But the cause of falsity or non-existence is the diversity and difference of the same proposition, which is a non-cause, from the proposition which truly is the cause of inference or conclusion.

CHAPTER XVIII. On the fallacy according to non-cause as cause.

Having these things, it is easy to determine concerning fallacies according to non-cause as cause as to the general cause of deception. For then these occur when, to the propositions premised, something adjunct to the premises from the number of propositions is taken, which in truth is not the cause of the inference or conclusion; and thus that is assumed with the premises as if on account of it, as on account of the cause of inference, a refutation is made, that is, an inference of the false, against the hypothesis of the respondent. But a paralogism or fallacy of this kind happens to syllogisms to the impossible, in which through a false contrary or contradictory a position or hypothesis previously concluded is destroyed through the showing of the falsity of some premises. For in syllogisms to the impossible it is always necessary to destroy something of those things which have been posited in the prior syllogism; and therefore it is necessary in these to multiply propositions, among which that one which is a non-cause as cause is latently introduced. Therefore if that proposition which is a non-cause as cause is numbered among the necessary ones, or among the necessary propositions which are necessary for the inference of the false thing from which the respondent's hypothesis must be destroyed, or in the interrogations, because a dialectical proposition is an interrogation, as was determined in the first book of the Topics; and it is numbered among them in the argument to which the impossible happens or follows, for this is the second argument and not the first, namely that from the false thing inferred it destroys the hypothesis, it will often seem to the deceived respondent that a refutation is made as to the inference of the opposite of the hypothesis itself by which the respondent is refuted on account of this, although it is not made on account of this. And thus as cause it moves toward deceiving, and as non-cause it is the principle of falsity, because the inference is not made on account of it; but when it has been removed the impossible would follow more abundantly.

But an example of this is that we say that the proposed point of the opposite is to show that soul and life are not the same; for concluding a necessary false thing, one must take false propositions from which that false thing necessarily follows by which the hypothesis saying that soul and life are the same is terminated. And it is argued thus: soul and life are the same; but everything which is contrary to corruption is generation; but life is contrary to death, and consequently is contrary to corruption, because death also is corruption; therefore life is generation, and consequently to live is to be generated. But this is false, namely that to live is to be generated; therefore the first thing also is false, namely that soul and life are the same. And Aristotle says this not in the same order, but more obscurely thus: As, since, supply, it is shown thus, that soul and life are not the same through the opposite false thing. For if generation is contrary to corruption generally, and generation and corruption are taken insofar as they are opposed motions in their terms, because a motion is said to be opposed or contrary to a motion with respect to the terms, then it would follow that to some corruption, which is the death of a living thing or dissolution, some generation will be contrary, which cannot be anything except life; for death is corruption and is contrary to life; wherefore, or therefore, life will be a certain generation, and to live will be to be generated. But this is impossible; therefore soul and life are not the same. And this has not been syllogized from this proposition, soul and life are the same. The proof of this is that the same impossible follows from the other propositions taken and premised, even if one of the opponents does not say, that is, does not place with the premises, this proposition, soul and life are the same, but only says and places in the premises that life is contrary to death, and this, that death is corruption, and that generation is the proper contrary to corruption. And thus this, soul and life are the same, was not the cause of the inference, namely of non-being, because it communicates with this, life and death are contraries, in a term signifying the same in each.

It is also clear from these things that reasons of this kind are not simply, that is, wholly, nonsyllogized, because the first conclusion of the false thing has truly been syllogized from false premises; but as to the proposed point they are nonsyllogized, that is, for destroying the hypothesis, because the hypothesis is impertinent to the other assumed propositions. But an impertinent proposition does not destroy the other, because it is impertinent to the inference. And this difficulty of not discerning the true cause of inference from that which is non-cause as cause, when it has been taken, because for the most part the same thing is hidden no less from the interrogators or opponents themselves than from the respondents themselves; and this is an example of non-cause as cause.

But in this example there are multiple propositions which must be distinguished thus: for when it is said that death and life are contraries, it must be distinguished, because death can mean the motion of dissolution of soul from body, or the term of that dissolution; and thus it is not corruption, but then it is to be corrupted. In the first way death and life are not contraries, because what is corrupted, so long as it is being corrupted, still lives; but contraries cannot be at the same time in the same thing. But if death is said in the second way as the term of dissolution, then life and death again are not contraries, but opposites as privation and habit; and thus in every way this is false, death and life are contraries, and it is simply false. Hence also above in the argumentation this should not have been destroyed, soul and life are the same, but this: death and life are contraries.

But from the things introduced afterward it follows that this fallacy does not happen in an ostensive syllogism. Hence here: every man is animal; and the sun is in Cancer, or the sun is greater than the earth; therefore Socrates runs. This is not the fallacy according to non-cause as cause, because this proposition, the sun is greater than the earth, neither is the cause of the conclusion nor can be the cause. But in the fallacy of non-cause as cause, the proposition which is a non-cause communicates with that which is a cause; and therefore it can be a cause.

But perhaps someone will object against this, saying that in truth in the said example there are two argumentations, the first of which is ostensive of the false, the second destructive of the hypothesis. For the first is this: soul and life are the same; to any corruption generation is contrary; but death is corruption; therefore to death generation is contrary; therefore to live is to be generated. This is the first argument and is ostensive of that false thing, that to live is to be generated. But the second, which is for destroying the hypothesis, is such: this conclusion, to live is to be generated, is false and impossible; therefore the hypothesis from which it follows, namely that soul and life are the same, is impossible. And it is clear that in the first argumentation among the premises that proposition which is a non-cause is posited; and thus in an ostensive syllogism there will be non-cause as cause, and it is not posited in the second argument; therefore it is not in a syllogism to the impossible, but in an ostensive one. But to this, according to the things which were said in the preceding chapter, one must say that although the proposition which is non-cause as cause is placed among the premises of the prior argumentation, which in truth is ostensive, nevertheless it ought not be denominated from it, because it is finally not posited for showing the first conclusion, but rather so that from that the hypothesis may be inferred through the second syllogism.

CHAPTER XIX. On the modes of the fallacy according to non-cause as cause.

But the modes of the fallacy must be multiplied according to the number of their formation. And there are two modes. One is according as a non-cause can communicate in some term with the propositions which are causes of the conclusion; for if it communicated with them in nothing, then it could not be a non-cause as cause. But if the hypothesis or proposition which is not the cause communicates in one of the terms with the propositions which are causes of the false conclusion, it will communicate either in the subject or in the predicate. And according to those communications two modes of paralogizing are formed: namely one when the non-cause as cause communicates in subject with the propositions which are the cause, so that in some one of the propositions which are causes the subject of the hypothesis is taken; and thus there is one and the first mode of deceiving. For just as this hypothesis, every stone is animal, is supposed, so let it be concluded that every man is stone, thus: every pearl is stone; every man is a pearl; therefore every man is a stone. This is impossible, but it does not follow because of the hypothesis; for when it has been removed, the same impossible still follows. And Aristotle posits this mode before the end of the second book of the Prior Analytics in general terms, positing this hypothesis, every B is A; therefore, if C is taken under B, not indeed as an inferior under a superior, as man under animal, but so that in the syllogism C becomes the subject of B, and D is taken under C, so that it becomes subject to it in the same way as before, thus: every C is B; every D is C; it follows that every D is B. Although this is false, nevertheless it is not false or does not follow because of the hypothesis; and this is the first mode. And that is plain if it is posited in special terms, that A is animal, B stone, C pearl, and D man; for then the hypothesis is: every stone is animal. With this supposed, every man is concluded to be stone thus: every pearl is stone; every man is a pearl; therefore every man is a stone. And this indeed is impossible, but it does not happen because of the hypothesis.

But if the premises showing the impossible communicate with the predicate of the hypothesis, thus there will be the second mode, and the example is such: let the hypothesis be as before, that every stone is animal; with this supposed let it be concluded that animal is inanimate, thus: every body is inanimate; every animal is a body; therefore every animal is inanimate. This conclusion is impossible, but it does not follow from the hypothesis. For when the hypothesis has been removed, the same conclusion still follows. But Aristotle at the end of the second book of the Prior Analytics posits general terms concerning this, that the hypothesis is, every B is A, and E is taken above A, so that it is its predicate and A the subject; and above E in the same way F is taken, so that F is predicated and E is subjected in the syllogism; and it is argued with the hypothesis supposed, thus: every B is A, this is the hypothesis; every E is F; every A is E; therefore every A is F. For this conclusion is false; nevertheless it does not follow because of the hypothesis; and therefore the hypothesis is non-cause as cause. And this is plain in special terms, as was said, if animal is understood through A, stone through B, inanimate through F, and body through E, and it is deduced as was said a little before.

Thus therefore it is clear that there are two modes of paralogizing according to this fallacy: one when the syllogism to the impossible communicates with the subject of the hypothesis, and the other when the same syllogism communicates with the predicate of the hypothesis. And there cannot be more, because if the proposition or hypothesis communicated with the propositions of the syllogism to the impossible in each term, so that the hypothesis takes both the subject and the predicate from those propositions which belong to the syllogism to the impossible, then this fallacy does not occur, because then from the hypothesis itself the false thing which is concluded follows of necessity, just as from the propositions of the syllogism. And indeed the example introduced suffices for each of these modes; for if the syllogism to the impossible is taken with respect to communication in this term, life, then life can be predicated and soul subjected in the hypothesis, and thus it destroys the example in the second mode, because then the syllogism to the impossible is joined to the predicate of the hypothesis. Or this which I say, life, can be subjected and soul predicated, and then it responds to the example in the first mode, because then the syllogism to the impossible is joined to the subject of the hypothesis. Thus therefore there are two modes according to this fallacy.

But one must know here that some ask concerning those speeches which Aristotle says are not simply syllogized, whether they are so with respect to the first conclusion or with respect to the second; and they say that those speeches are simply nonsyllogized. And if they ought to be reduced to syllogistic form, they must be formed thus: everything that is contrary to corruption is generation; life is contrary to corruption through the fact that it is contrary to death, which is corruption; therefore life is generation; therefore to live is to be generated. This is false, because what lives is not being generated, but has already been generated.

And they respond to this and say that the first is false; for they say that not generation alone is contrary to corruption, but also creation, through which, just as through generation, a thing comes forth and is changed from non-being to being. But this is nothing, because if creation and corruption are taken as contraries, then they must be apt to occur around the same thing, which can be subjected to creation and corruption. Hence what they say is not physical.

Therefore others say that this is false, death and life are contraries; for these, namely death and life, are not opposed contrarily, but as privation and habit. But according to this response it is not avoided that the false conclusion still follows, thus: everything that is privatively opposed to corruption is generation; life is privatively opposed to corruption, because to death which is corruption; therefore life is generation; therefore to live is to be generated. Also as before, the hypothesis is destroyed.

Therefore others say that this is false, death is corruption; and they say that the reason for this is that nothing which follows as term and end from some motion or from some change can be called that motion or that change, so that motion or change is predicated of that thing. For life follows upon the generation of an animal, and therefore life itself is not generation; for as was said before, that which is generated does not live, but when it lives, it has already been generated. It is also the same way concerning corruption: for first the animal is corrupted, and after corruption death follows, and then the animal is in corrupted being. Therefore, since corruption is a certain change upon which death follows, death cannot be corruption; and therefore the proposition which says that death is corruption is false. And from that false proposition together with other false premises the false conclusion follows. For it does not follow, if death and life are contraries, therefore life is generation, unless either this is posited or understood: death is corruption. And this is the same as what was said before in the distinction of propositions. Hence, as was said above, those speeches are syllogized as to the first false conclusion, for a false conclusion follows necessarily from the premises, and it is a good ostensive syllogism showing the false from false things; but as to the second conclusion, which nevertheless is principally intended, those speeches are simply nonsyllogized. For from an impossible conclusion it does not follow that the hypothesis must simply be destroyed, because the hypothesis simply is not the cause of the impossible conclusion; and thus as to that conclusion which is principally intended, those speeches are nonsyllogized, and thus nonsyllogized as to the proposed point or to the intention.

One must also attend that between the consequent or fallacy of the consequent and non-cause as cause there is an agreement: first, that just as in the fallacy of the consequent there are always two consequences, one good and the other bad, so also in non-cause as cause there are two consequences of two arguments, one good which is ostensive of the false, the other bad which from the false is destructive of the hypothesis. Secondly in this, that just as in the consequent there is a certain reciprocation of consequences, as from antecedent to consequent and conversely, so in non-cause as cause there is a certain reciprocation from the hypothesis to the concluded false thing, and from the false to the destruction of the hypothesis. Thus therefore let it have been determined concerning the paralogism according to the consequent and concerning those which are according to non-cause as cause.

CHAPTER XX. On the preliminaries for syllogizing the fallacy according to several questions as one.

For understanding the fallacy according to several questions as one, it must be noted beforehand and accepted from the Topics what a question is, and in what it differs from a proposition and an enunciation. For a question, as was said in the Topics, is a probable proposition put forward with the mark of questioning. But an enunciation, as was said in On Interpretation, is a speech enunciating something about something. But a proposition, as in the first book of the Prior Analytics, is an enunciative speech of something about something for another, posited in order to the form of argumentation and especially of syllogism according to the principle from which the inference of the consequent is made, which is the conclusion, according as the conclusion is an enunciation or proposition proved by a middle or by middles. And thus it is clear that interrogation adds over a dialectical proposition, which is probable, the mode of questioning and the respondent's assent concerning the composition, whether the predicate is in the subject, as when it is said, is this true: man runs? or do you think man runs? or is man animal, or something else such as this?

But what the difference of interrogation is, when the mark of questioning is placed at the composition, and when at the whole proposition or upon the respondent's consent, was sufficiently said in the first book of the Topics¹. For if it is asked thus, does man run? the mark of interrogation is placed at the composition, and such a speech is called a question. But if I say thus, do you think man runs? the mark of interrogation is not borne to the composition, because those words expressly affirm; but the mark of interrogation awaits the respondent's consent into the composition. And therefore such an interrogation is not a question, but a proposition in which, because of the non-necessary inherence of the predicate in the subject, it is asked whether the respondent assents. Therefore question and conclusion, as Boethius says, do not differ according to substance, but in mode, because what in doubtful matters is a question, this same thing, proved by one middle or several and inferred from them, is made a conclusion. But interrogation also differs from proposition in mode and not in substance, because interrogation is a proposition with a mark of interrogation falling upon the whole proposition which is not about the respondent's consent. Thus also enunciation differs from proposition and interrogation in mode alone, because enunciation simply indicates or enunciates some predicate about some subject; but proposition is the same enunciation when, under the form of the first argument of a syllogism, it is posited for another thing which is inferred according to the relation of principle from this. Hence conclusion has itself toward proposition as the thing inferred and principled from it; but proposition has itself toward conclusion as inferior and its principle; but enunciation is the substance of proposition and of interrogation and of conclusion, taken without such modes.

Having seen these things, those things which were said in On Interpretation about the unity and plurality of enunciation must be recalled. For it was said there that an enunciation is simply one in which simply one thing is enunciated of one thing, that is, one predicate of one subject not only in voice, but in truth of the thing, because if unity of voice sufficed, then a proposition in which an equivocal name is subjected or predicated would be simply one; and this is false, as was shown in On Interpretation. And therefore for the unity of a proposition there are required both unity of the thing signified in the predicate and subject, and also that the discourse be referred to one thing, even if the discourse itself is several words, as is clear in this: man is a rational mortal animal, which is one, because one thing is predicated of one thing; because rational and mortal are referred to a simply one thing, although several in discourse, because the following difference is in the preceding as act in potency. But act and potency constitute one and the same thing, and are referred to one and the same thing.

But although unity is manifold, as Aristotle says in Metaphysics X² and Boethius in the book On Unity and One, namely unity of analogy, and unity of genus, and unity of species, and unity in number³, and this unity is divided into several things, namely of definition and of the defined, and of indivision through a proper accident, and generally the unity of accident and subject, as Boethius says, in those things in which diversity in numbering is not found; nevertheless, when proposition or interrogation or enunciation is called one, it is taken commonly for all those unities. Hence this is one: substance is being; and this one: man is animal; and this one: Socrates is man: