LESSON XI

Whether "Possible To Be" Follows Upon "Necessary To Be"

             22b 29 But it may be questioned whether "possible to be" follows upon "necessary to be." Yet if not, the contradictory, "not possible to be," would have to follow; or if someone should say that this is not the contradictory, then "possible not to be." But both of these are false in regard to that which is necessary to be.

             22b 33 On the other hand, it seems possible for the same thing to be cut and not to be cut, and to be and not to be, and thus it would follow that what is necessary to be is possible not to be, which is false.

             22b 36 It is evident by now that not every possibility of being or walking is one that admits of opposites. There are those of which this is not true. First of all, this is not true of potentialities which are not according to reason, as fire, which has an irrational potentiality, the power to heat. Potentialities that are in conjunction with reason are capable of more than one and of contraries; but not all irrational potentialities are capable of contraries; as has been said, fire does not have the potentiality to heat and not to heat, nor does anything that always acts have this potentiality; however, even some of the irrational potencies are simultaneously capable of opposites. We have spoken of this in order to show that not every potentiality is a potentiality to opposites, not even all those that are called potentialities according to the same notion.

             1. Now that he has explained the consequents of modals, Aristotle raises a question about one of the points that has already been determined, namely, that the possible follows upon the necessary. He first raises the question and then settles it where he says, It is evident by now that not every possibility of being or walking is one that admits of opposites, etc. Secondly, he establishes another order of the same consequents from the determination of the present question, where he says Indeed the necessary and not necessary may well be the principle of all that is or is not, etc.

             First, then, he raises the question: But it may be questioned whether "possible to be" follows upon "necessary to be." Secondly, he argues to the affirmative part: Yet if not, the contradictory, "not possible to be," would have to follow, as was deduced earlier, for either the affirmation or the negation is true of anything. And if someone should say "not possible to be" is not the contradictory of "possible to be," because he wants to avoid the conclusion by saying that neither of these follows upon "necessary to be," this may be conceded, although what he says is false. But then he will have to say that the contradictory of "possible to be" is "possible not to be," for the contradictory of "possible to be" has to be either "not possible to be" or "possible not to be." But if he says this, he will fall into another error, for it is false to say it is not possible to be of that which is necessary to be, and it is false to say it is possible not to be. Consequently, neither follows upon it, for no enunciation follows upon an enunciation whose truth it destroys. Therefore, "possible to be" follows upon "necessary to be."

             2. Thirdly, he argues to the negative part where he says, On the other hand, it seems possible for the same thing to be cut and not to be cut, etc. His argument is as follows: If "possible to be" follows upon "necessary to be," then, since "possible not to be" follows upon the possible (through conversion to the opposite quality, as is said in Priorum, for the same thing is possible to be and not to be), from first to last it will follow that the necessary is possible not to be, which is clearly false.

             In this argument, Aristotle supplies a hypothesis opposed to the position that possible to be follows upon necessary to be: On the other hand, it seems possible for the same thing to be cut and not to be cut, for instance a garment, and to be and not to be, for instance a house. Therefore, from first to last, necessary to be will be possible not to be. But this is false. Therefore, the hypothesis that the possible follows upon the necessary is false.

             3. When he says, It is evident by now that not every possibility of being or walking, etc., he answers the question he proposed. First, he manifests the truth simply, then applies it to the question where he says, "So it is not true to say the latter possible of what is necessary simply, etc.

             First, then, he proposes the truth he is going to explain: It is evident by now that not every possibility of being or walking, i.e., of operating; that is, not everything possible according to first or second act admits of opposites, i.e., has access to opposites; there are some possibles of which it is not true to say that they are capable of opposites.

             Then, since the possible arises from potency, he manifests how potency is related to opposites; for it will be clear from this how the possible is related to opposites. First he manifests this in potencies having the same notion; secondly, in those that are called potencies equivocally where he says, But some are called potentialities equivocally, etc. With respect to the way in which potencies of the same specific notion are related to opposites, he does three things. First of all he manifests how an irrational potency is related to opposites; an irrational potency, he says, is not a potency that is capable of opposites.

             4. It must be noted in this connection that active potency, since it is the principle by which we act on something else, is divided into rational and irrational potency, as is said in IX Metaphysicae. Rational potency operates in connection with reason and choice; for example, the art of medicine by which the physician, knowing and willing what is expedient in healing an illness, applies a remedy. Irrational potency operates according to its own natural disposition, not according to reason and liberty; for example, the heat of fire is an irrational potency, because it heats, not as it knows and wills, but as its nature requires.

             In the Metaphysics, a twofold difference between these potencies is assigned which is relevant here. The first is that an irrational active potency is not capable of two opposites, but is determined to one opposite, whether "opposite" is taken contradictorily or contrarily; e.g., heat cannot heat and not heat, which are opposed contradictorily; nor can it heat and cool, which are contraries, but is determined to heating. Understand this per se, for heat can cool accidentally, either by destroying the matter of heat, namely, the humid, or through alternation of the contrary. It also has the potentiality not to heat accidentally, if that which can be heated is lacking. A rational potency, on the other hand, is capable of opposites, both contradictorily and contrarily; for by the art of medicine the physician can employ a remedy and not employ it, which are contradictories, and employ healing and harmful remedies, which are contraries.

             The second difference is that an irrational active potency necessarily operates when a subject is present and impediments are withdrawn; for heat necessarily heats when a subject that can be heated is present, and nothing impedes it. A rational potency, however, does not necessarily operate when a subject is present; e.g., when a sick man is present the physician is not forced to employ a remedy.

             5. The reasons for these differences are given in the Metaphysics, but let us return to the text. Explaining how an irrational potency is related to opposites, he says, First of all, this is not true, i.e., it is not true to say that there is a potency to opposites in those which are not according to reason, i.e., whose power is through irrational potencies; as fire which is calefactive, i.e., capable of heating, has this power, i.e., this irrational potentiality, since it is not able to cool, nor is it in its power to heat and not to heat.

             Note that he speaks here of a first kind. This is in relation to a second genus of the possible which he will speak of later, in which there is not a potency to opposites either.

             6. Secondly, he shows how a rational potency is related to opposites, i.e., it is capable of opposites: Therefore potentialities that are in conjunction with reason, i.e., rational potencies, are capable of contraries, not only of two, but even of many; for example, a physician by the art of medicine can employ many pairs of contraries and he can abstain from doing or not doing many things.

             He begins with "therefore" so as to imply that this follows from what has been said. The argument would be: properties of opposites are opposites; an irrational potency, because it is irrational, does not extend itself to opposites; therefore a rational potency, because it is rational, has access to opposites.

             7. Thirdly, he explains what he has said about irrational potencies. He will assign the reason for doing this later. He makes the point that what he has said about irrational potentiality, i.e., that it is not capable of opposites, is not true universally, but particularly.

             It should be noted here that irrational potency is divided into active potency, which is the principle of acting, and passive potency, which is the principle of being acted upon; e.g., potency to heat is divided into potentiality to heat and potentiality to be heated.

             Now it is true that active irrational potencies are not capable of opposites, as was explained. This is not true, however, of passive potencies, for what can be heated can also be cooled, because the matter is the same, i.e., the passive potency of contraries, as is said in II De caelo et mundo. It can also not be heated, since the subject of privation and of form is the same, as is said in I Physic.

             Therefore, in explaining about irrational potencies, he says, But not all irrational potentialities should be understood to be excluded from the capacity of opposites. Those like the potentiality of fire to heat are to be excluded (for it is evident that fire cannot not heat), and universally, whatever others are potencies of such a kind that they always act, i.e., the ones that of themselves cannot not act, but are necessitated by their form always to act. All active irrational potencies are of this kind, as we have explained. There are others, however, of such a condition that even though they are irrational potencies (i.e., passive) are simultaneously capable of certain opposites; for example, air can be heated and cooled.

             "Simultaneously" modifies "are capable" and not "opposites." What he means is that the thing simultaneously has a passive potency to each opposite, and not that it has a passive potency to have both opposites simultaneously, for it is impossible to have opposites at one and the same time. Hence it is customary and correct to say that in these there is simultaneity of potency, not potency of simultaneity. Therefore, irrational potency is excluded from the capacity of opposites, not completely, but according to its part, namely, according to active potencies.

             8. Because it might seem superfluous to have added the differences between active and passive irrational potencies, since enough had already been said to show that not every potency is of opposites, Aristotle gives the reason for this. It was not only to make it known that not every potency is of opposites, speaking of potency most commonly, but also that not all that are called potencies according to the same species are capable of opposites. For all irrational potencies are included under one species of irrational potency, and yet not all are capable of opposites, but only the passive potencies. It was not superfluous, therefore, to point out the difference between passive and active irrational potencies, since this was necessary in order to show that not all potencies of the same species are capable of opposites.

             "This" in the phrase "this has been said" could designate each difference, the one between rational and irrational potencies, and the one between active and passive irrational potencies. The meaning is, then, that we have said this to show that not every potentiality which is said according to the same notion of physical power--namely, because it can be in something as rational and irrational--not even every potentiality which is contained under the same species, as active and passive under the species irrational, is capable of opposites.