Aristotle: Metaphysics Book 9

[1045b] [27]

We have now dealt with Being in the primary sense, to which all the other categories of being are related; i.e. substance. For it is from the concept of substance that all the other modes of being take their meaning; both quantity and quality and all other such terms; for they will all involve the concept of substance, as we stated it in the beginning of our discussion.1And since the senses of being are analyzable2 not only into substance or quality or quantity, but also in accordance with potentiality and actuality and function, let us also gain a clear understanding about potentiality and actuality; and first about potentiality in the sense which is most proper to the word, but not most useful for our present purpose— [1046a] [1] for potentiality and actuality extend beyond the sphere of terms which only refer to motion.When we have discussed this sense of potentiality we will, in the course of our definitions of actuality,3 explain the others also.

We have made it plain elsewhere4 that “potentiality” and “can” have several senses.All senses which are merely equivocal may be dismissed; for some are used by analogy, as in geometry,5 and we call things possible or impossible because they “are” or “are not” in some particular way. But the potentialities which conform to the same type are all principles, and derive their meaning from one primary sense of potency, which is the source of change in some other thing, or in the same thing qua other.

One kind of potentiality is the power of being affected; the principle in the patient itself which initiates a passive change in it by the action of some other thing, or of itself qua other. Another is a positive state of impassivity in respect of deterioration or destruction by something else or by itself qua something else; i.e. by a transformatory principle—for all these definitions contain the formula of the primary sense of potentiality.Again, all these potentialities are so called either because they merely act or are acted upon in a particular way, or because they do so well . Hence in their formulae also the formulae of potentiality in the senses previously described are present in some degree.

Clearly, then, in one sense the potentiality for acting and being acted upon is one [20] (for a thing is “capable” both because it itself possesses the power of being acted upon, and also because something else has the power of being acted upon by it);and in another sense it is not; for it is partly in the patient (for it is because it contains a certain principle, and because even the matter is a kind of principle, that the patient is acted upon; i.e., one thing is acted upon by another: oily stuff is inflammable, and stuff which yields in a certain way is breakable, and similarly in other cases)—and partly in the agent; e.g. heat and the art of building: the former in that which produces heat, and the latter in that which builds. Hence in so far as it is a natural unity, nothing is acted upon by itself; because it is one, and not a separate thing.

“Incapacity” and “the incapable” is the privation contrary to “capacity” in this sense; so that every “capacity” has a contrary incapacity for producing the same result in respect of the same subject.

Privation has several senses6—it is applied (1.) to anything which does not possess a certain attribute; (2.) to that which would naturally possess it, but does not; either (a) in general, or (b) when it would naturally possess it; and either (1) in a particular way, e.g. entirely, or (2) in any way at all. And in some cases if things which would naturally possess some attribute lack it as the result of constraint, we say that they are “deprived.”

Since some of these principles are inherent in inanimate things, and others in animate things and in the soul and in the rational part of the soul, [1046b] [1] it is clear that some of the potencies also will be irrational and some rational. Hence all arts, i.e. the productive sciences, are potencies; because they are principles of change in another thing, or in the artist himself qua other.

Every rational potency admits equally of contrary results, but irrational potencies admit of one result only. E.g., heat can only produce heat, but medical science can produce disease and health. The reason of this is that science is a rational account, and the same account explains both the thing and its privation, though not in the same way; and in one sense it applies to both, and in another sense rather to the actual fact.Therefore such sciences must treat of contraries—essentially of the one, and non-essentially of the other; for the rational account also applies essentially to the one, but to the other in a kind of accidental way, since it is by negation and removal that it throws light on the contrary. For the contrary is the primary privation,7 and this is the removal of that to which it is contrary.8And since contrary attributes cannot be induced in the same subject, and science is a potency which depends upon the possession of a rational formula, and the soul contains a principle of motion, it follows that whereas “the salutary” can only produce health, and “the calefactory” only heat, and “the frigorific” only cold, [20] the scientific man can produce both contrary results.For the rational account includes both, though not in the same way; and it is in the soul, which contains a principle of motion, and will therefore, by means of the same principle, set both processes in motion, by linking them with the same rational account. Hence things which have a rational potency produce results contrary to those of things whose potency is irrational9; for the results of the former are included under one principle, the rational account.It is evident also that whereas the power of merely producing (or suffering) a given effect is implied in the power of producing that effect well , the contrary is not always true; for that which produces an effect well must also produce it, but that which merely produces a given effect does not necessarily produce it well.

There are some, e.g. the Megaric school,10 who say that a thing only has potency when it functions, and that when it is not functioning it has no potency. E.g., they say that a man who is not building cannot build, but only the man who is building, and at the moment when he is building; and similarly in the other cases.It is not difficult to see the absurd consequences of this theory. Obviously a man will not be a builder unless he is building, because “to be a builder” is “to be capable of building”; and the same will be true of the other arts.If, therefore, it is impossible to possess these arts without learning them at some time and having grasped them, [1047a] [1] and impossible not to possess them without having lost them at some time (through forgetfulness or some affection or the lapse of time; not, of course, through the destruction of the object of the art,11 because it exists always), when the artist ceases to practice his art, he will not possess it;and if he immediately starts building again, how will he have re-acquired the art?

The same is true of inanimate things. Neither the cold nor the hot nor the sweet nor in general any sensible thing will exist unless we are perceiving it (and so the result will be that they are affirming Protagoras' theory12). Indeed, nothing will have the faculty of sensation unless it is perceiving, i.e. actually employing the faculty.If, then, that is blind which has not sight, though it would naturally have it, and when it would naturally have it, and while it still exists, the same people will be blind many times a day; and deaf too.

Further, if that which is deprived of its potency is incapable, that which is not happening will be incapable of happening; and he who says that that which is incapable of happening is or will be, will be in error, for this is what “incapable” meant.13Thus these theories do away with both motion and generation; for that which is standing will always stand, and that which is sitting will always sit; because if it is sitting it will not get up, since it is impossible that anything which is incapable of getting up should get up.Since, then, we cannot maintain this, obviously potentiality and actuality are different. But these theories make potentiality and actuality identical; [20] hence it is no small thing that they are trying to abolish.

Thus it is possible that a thing may be capable of being and yet not be, and capable of not being and yet be; and similarly in the other categories that which is capable of walking may not walk, and that which is capable of not walking may walk.A thing is capable of doing something if there is nothing impossible in its having the actuality of that of which it is said to have the potentiality. I mean, e.g., that if a thing is capable of sitting and is not prevented from sitting, there is nothing impossible in its actually sitting; and similarly if it is capable of being moved or moving or standing or making to stand or being or becoming or not being or not becoming.

The term “actuality,” with its implication of “complete reality,” has been extended from motions, to which it properly belongs, to other things; for it is agreed that actuality is properly motion.Hence people do not invest non-existent things with motion, although they do invest them with certain other predicates. E.g., they say that non-existent things are conceivable and desirable, but not that they are in motion. This is because, although these things do not exist actually, they will exist actually; [1047b] [1] for some non-existent things exist potentially; yet they do not exist, because they do not exist in complete reality.

Now if, as we have said, that is possible which does not involve an impossibility, obviously it cannot be true to say that so-and-so is possible, but will not be, this view entirely loses sight of the instances of impossibility.14 I mean, suppose that someone—i.e. the sort of man who does not take the impossible into account—were to say that it is possible to measure the diagonal of a square, but that it will not be measured, because there is nothing to prevent a thing which is capable of being or coming to be from neither being nor being likely ever to be.But from our premisses this necessarily follows: that if we are to assume that which is not, but is possible, to be or to have come to be, nothing impossible must be involved. But in this case something impossible will take place; for the measuring of the diagonal is impossible.

The false is of course not the same as the impossible; for although it is false that you are now standing, it is not impossible.At the same time it is also clear that if B must be real if A is, then if it is possible for A to be real, it must also be possible for B to be real; for even if B is not necessarily possible, there is nothing to prevent its being possible. Let A, then, be possible. Then when A was possible, if A was assumed to be real, nothing impossible was involved; but B was necessarily real too. [20] But ex hypothesi B was impossible. Let B be impossible.Then if B is impossible, A must also be impossible. But A was by definition possible. Therefore so is B.

If, therefore, A is possible, B will also be possible; that is if their relation was such that if A is real, B must be real.Then if, A and B being thus related, B is not possible on this condition, A and B will not be related as we assumed; and if when A is possible B is necessarily possible, then if A is real B must be real too. For to say that B must be possible if A is possible means that if A is real at the time when and in the way in which it was assumed that it was possible for it to be real, then B must be real at that time and in that way.

Since all potencies are either innate, like the senses, or acquired by practice, like flute-playing, or by study, as in the arts, some—such as are acquired by practice or a rational formula—we can only possess when we have first exercised them15; in the case of others which are not of this kind and which imply passivity, this is not necessary. [1048a] [1]

Since anything which is possible is something possible at some time and in some way, and with any other qualifications which are necessarily included in the definition; and since some things can set up processes rationally and have rational potencies, while others are irrational and have irrational potencies; and since the former class can only belong to a living thing, whereas the latter can belong both to living and to inanimate things: it follows that as for potencies of the latter kind, when the agent and the patient meet in accordance with the potency in question, the one must act and the other be acted upon; but in the former kind of potency this is not necessary, for whereas each single potency of the latter kind is productive of a single effect, those of the former kind are productive of contrary effects,16 so that one potency will produce at the same time contrary effects.17But this is impossible. Therefore there must be some other deciding factor, by which I mean desire or conscious choice. For whichever of two things an animal desires decisively it will do, when it is in circumstances appropriate to the potency and meets with that which admits of being acted upon. Therefore everything which is rationally capable, when it desires something of which it has the capability, and in the circumstances in which it has the capability, must do that thing.Now it has the capability when that which admits of being acted upon is present and is in a certain state; otherwise it will not be able to act. (To add the qualification “if nothing external prevents it” is no longer necessary; because the agent has the capability in so far as it is a capability of acting; and this is not in all, but in certain circumstances, in which external hindrances will be excluded; [20] for they are precluded by some of the positive qualifications in the definition.)Hence even if it wishes or desires to do two things or contrary things simultaneously, it will not do them, for it has not the capability to do them under these conditions, nor has it the capability of doing things simultaneously, since it will only do the things to which the capability applies and under the appropriate conditions.

Since we have now dealt with the kind of potency which is related to motion, let us now discuss actuality; what it is, and what its qualities are. For as we continue our analysis it will also become clear with regard to the potential that we apply the name not only to that whose nature it is to move or be moved by something else, either without qualification or in some definite way, but also in other senses; and it is on this account that in the course of our inquiry we have discussed these as well.

“Actuality” means the presence of the thing, not in the sense which we mean by “potentially.” We say that a thing is present potentially as Hermes is present in the wood, or the half-line in the whole, because it can be separated from it; and as we call even a man who is not studying “a scholar” if he is capable of studying. That which is present in the opposite sense to this is present actually.What we mean can be plainly seen in the particular cases by induction; we need not seek a definition for every term, but must comprehend the analogy: that as that which is actually building is to that which is capable of building, [1048b] [1] so is that which is awake to that which is asleep; and that which is seeing to that which has the eyes shut, but has the power of sight; and that which is differentiated out of matter to the matter; and the finished article to the raw material.Let actuality be defined by one member of this antithesis, and the potential by the other.

But things are not all said to exist actually in the same sense, but only by analogy—as A is in B or to B, so is C in or to D; for the relation is either that of motion to potentiality, or that of substance to some particular matter.

Infinity and void and other concepts of this kind are said to “be” potentially or actually in a different sense from the majority of existing things, e.g. that which sees, or walks, or is seen.For in these latter cases the predication may sometimes be truly made without qualification, since “that which is seen” is so called sometimes because it is seen and sometimes because it is capable of being seen; but the Infinite does not exist potentially in the sense that it will ever exist separately in actuality; it is separable only in knowledge. For the fact that the process of division never ceases makes this actuality exist potentially, but not separately.18

Since no action which has a limit is an end, but only a means to the end, as, e.g., the process of thinning; [20] and since the parts of the body themselves, when one is thinning them, are in motion in the sense that they are not already that which it is the object of the motion to make them, this process is not an action, or at least not a complete one, since it is not an end; it is the process which includes the end that is an action.E.g., at the same time we see and have seen, understand and have understood, think and have thought; but we cannot at the same time learn and have learnt, or become healthy and be healthy. We are living well and have lived well, we are happy and have been happy, at the same time; otherwise the process would have had to cease at some time, like the thinning-process; but it has not ceased at the present moment; we both are living and have lived.

Now of these processes we should call the one type motions, and the other actualizations.Every motion is incomplete—the processes of thinning, learning, walking, building—these are motions, and incomplete at that. For it is not the same thing which at the same time is walking and has walked, or is building and has built, or is becoming and has become, or is being moved and has been moved, but two different things; and that which is causing motion is different from that which has caused motion.But the same thing at the same time is seeing and has seen, is thinking and has thought. The latter kind of process, then, is what I mean by actualization, and the former what I mean by motion.

What the actual is, then, and what it is like, may be regarded as demonstrated from these and similar considerations.

We must, however, distinguish when a particular thing exists potentially, and when it does not; for it does not so exist at any and every time. [1049a] [1] E.g., is earth potentially a man? No, but rather when it has already become semen,19 and perhaps not even then; just as not everything can be healed by medicine, or even by chance, but there is some definite kind of thing which is capable of it, and this is that which is potentially healthy.

The definition of that which as a result of thought comes, from existing potentially, to exist actually, is that, when it has been willed, if no external influence hinders it, it comes to pass; and the condition in the case of the patient, i.e. in the person who is being healed, is that nothing in him should hinder the process. Similarly a house exists potentially if there is nothing in X, the matter, to prevent it from becoming a house, i.e., if there is nothing which must be added or removed or changed; then X is potentially a house;and similarly in all other cases where the generative principle is external. And in all cases where the generative principle is contained in the thing itself, one thing is potentially another when, if nothing external hinders, it will of itself become the other. E.g., the semen is not yet potentially a man; for it must further undergo a change in some other medium.20 But when, by its own generative principle, it has already come to have the necessary attributes, in this state it is now potentially a man, whereas in the former state it has need of another principle;just as earth is not yet potentially a statue, because it must undergo a change before it becomes bronze.

It seems that what we are describing is not a particular thing, but a definite material; e.g., a box is not wood, but wooden material,21 [20] and wood is not earth, but earthen material; and earth also is an illustration of our point if it is similarly not some other thing, but a definite material—it is always the latter term in this series which is, in the fullest sense, potentially something else.E.g., a box is not earth, nor earthen, but wooden; for it is this that is potentially a box, and this is the matter of the box—that is, wooden material in general is the matter of “box” in general, whereas the matter of a particular box is a particular piece of wood.

If there is some primary stuff, which is not further called the material of some other thing, this is primary matter. E.g., if earth is “made of air,” and air is not fire, but “made of fire,” then fire is primary matter, not being an individual thing.For the subject or substrate is distinguishable into two kinds by either being or not being an individual thing. Take for example as the subject of the attributes “man,” or “body” or “soul,” and as an attribute “cultured” or “white.” Now the subject, when culture is induced in it, is called not “culture” but “cultured,” and the man is called not whiteness but white; nor is he called “ambulation” or “motion,” but “walking” or “moving”; just as we said that things are of a definite material.Thus where “subject” has this sense, the ultimate substrate is substance; but where it has not this sense, and the predicate is a form or individuality, the ultimate substrate is matter or material substance. It is quite proper that both matter and attributes should be described by a derivative predicate, [1049b] [1] since they are both indefinite.

Thus it has now been stated when a thing should be said to exist potentially, and when it should not.

Now since we have distinguished22 the several senses of priority, it is obvious that actuality is prior to potentiality. By potentiality I mean not that which we have defined as “a principle of change which is in something other than the thing changed, or in that same thing qua other,” but in general any principle of motion or of rest; for nature also is in the same genus as potentiality, because it is a principle of motion, although not in some other thing, but in the thing itself qua itself.23To every potentiality of this kind actuality is prior, both in formula and in substance; in time it is sometimes prior and sometimes not.

That actuality is prior in formula is evident; for it is because it can be actualized that the potential, in the primary sense, is potential, I mean, e.g., that the potentially constructive is that which can construct, the potentially seeing that which can see, and the potentially visible that which can be seen.The same principle holds in all other cases too, so that the formula and knowledge of the actual must precede the knowledge of the potential.

In time it is prior in this sense: the actual is prior to the potential with which it is formally identical, but not to that with which it is identical numerically.What I mean is this: [20] that the matter and the seed and the thing which is capable of seeing, which are potentially a man and corn and seeing, but are not yet so actually, are prior in time to the individual man and corn and seeing subject which already exist in actuality.But prior in time to these potential entities are other actual entities from which the former are generated; for the actually existent is always generated from the potentially existent by something which is actually existent—e.g., man by man, cultured by cultured—there is always some prime mover; and that which initiates motion exists already in actuality.

We have said24 in our discussion of substance that everything which is generated is generated from something and by something; and by something formally identical with itself.Hence it seems impossible that a man can be a builder if he has never built, or a harpist if he has never played a harp; because he who learns to play the harp learns by playing it, and similarly in all other cases.This was the origin of the sophists' quibble that a man who does not know a given science will be doing that which is the object of that science, because the learner does not know the science. But since something of that which is being generated is already generated, and something of that which is being moved as a whole is already moved (this is demonstrated in our discussion on Motion25), [1050a] [1] presumably the learner too must possess something of the science.At any rate from this argument it is clear that actuality is prior to potentiality in this sense too, i.e. in respect of generation and time.

But it is also prior in substantiality; (a) because things which are posterior in generation are prior in form and substantiality; e.g., adult is prior to child, and man to semen, because the one already possesses the form, but the other does not;and (b) because everything which is generated moves towards a principle, i.e. its end . For the object of a thing is its principle; and generation has as its object the end . And the actuality is the end, and it is for the sake of this that the potentiality is acquired; for animals do not see in order that they may have sight, but have sight in order that they may see.Similarly men possess the art of building in order that they may build, and the power of speculation that they may speculate; they do not speculate in order that they may have the power of speculation—except those who are learning by practice; and they do not really speculate, but only in a limited sense, or about a subject about which they have no desire to speculate.

Further, matter exists potentially, because it may attain to the form; but when it exists actually, it is then in the form. The same applies in all other cases, including those where the end is motion.Hence, just as teachers think that they have achieved their end when they have exhibited their pupil performing, so it is with nature. For if this is not so, [20] it will be another case of “Pauson's Hermes”26; it will be impossible to say whether the knowledge is in the pupil or outside him, as in the case of the Hermes. For the activity is the end, and the actuality is the activity; hence the term “actuality” is derived from “activity,” and tends to have the meaning of “complete reality.”

Now whereas in some cases the ultimate thing is the use of the faculty, as, e.g., in the case of sight seeing is the ultimate thing, and sight produces nothing else besides this; but in other cases something is produced, e.g. the art of building produces not only the act of building but a house; nevertheless in the one case the use of the faculty is the end, and in the other it is more truly the end than is the potentiality. For the act of building resides in the thing built; i.e., it comes to be and exists simultaneously with the house.

Thus in all cases where the result is something other than the exercise of the faculty, the actuality resides in the thing produced; e.g. the act of building in the thing built, the act of weaving in the thing woven, and so on; and in general the motion resides in the thing moved. But where there is no other result besides the actualization, the actualization resides in the subject; e.g. seeing in the seer, and speculation in the speculator, and life in the soul [1050b] [1] (and hence also happiness, since happiness is a particular kind of life). Evidently, therefore, substance or form is actuality. Thus it is obvious by this argument that actuality is prior in substantiality to potentiality; and that in point of time, as we have said, one actuality presupposes another right back to that of the prime mover in each case.

It is also prior in a deeper sense; because that which is eternal is prior in substantiality to that which is perishable, and nothing eternal is potential. The argument is as follows. Every potentiality is at the same time a potentiality for the opposite.27 For whereas that which is incapable of happening cannot happen to anything, everything which is capable may fail to be actualized.Therefore that which is capable of being may both be and not be. Therefore the same thing is capable both of being and of not being. But that which is capable of not being may possibly not be; and that which may possibly not be is perishable; either absolutely, or in the particular sense in which it is said that it may possibly not be; that is, in respect either of place or of quantity or of quality. “Absolutely” means in respect of substance.Hence nothing which is absolutely imperishable is absolutely potential (although there is no reason why it should not be potential in some particular respect; e.g. of quality or place); therefore all imperishable things are actual. Nor can anything which is of necessity be potential; and yet these things are primary, for if they did not exist, nothing would exist. [20] Nor can motion be potential, if there is any eternal motion. Nor, if there is anything eternally in motion, is it potentially in motion (except in respect of some starting-point or destination), and there is no reason why the matter of such a thing should not exist.Hence the sun and stars and the whole visible heaven are always active, and there is no fear that they will ever stop—a fear which the writers28 on physics entertain. Nor do the heavenly bodies tire in their activity; for motion does not imply for them, as it does for perishable things, the potentiality for the opposite, which makes the continuity of the motion distressing; this results when the substance is matter and potentiality, not actuality.

Imperishable things are resembled in this respect by things which are always undergoing transformation, such as earth and fire; for the latter too are always active, since they have their motion independently and in themselves.29 Other potentialities, according to the distinctions already made,30 all admit of the opposite result; for that which is capable of causing motion in a certain way can also cause it not in that way; that is if it acts rationally.The same irrational potentialities can only produce opposite results by their presence or absence.

Thus if there are any entities or substances such as the dialecticians31 describe the Ideas to be, there must be something which has much more knowledge than absolute knowledge, and much more mobility than motion; [1051a] [1] for they will be in a truer sense actualities, whereas knowledge and motion will be their potentialities.32 Thus it is obvious that actuality is prior both to potentiality and to every principle of change.

That a good actuality is both better and more estimable than a good potentiality will be obvious from the following arguments. Everything of which we speak as capable is alike capable of contrary results; e.g., that which we call capable of being well is alike capable of being ill, and has both potentialities at once; for the same potentiality admits of health and disease, or of rest and motion, or of building and of pulling down, or of being built and of falling down.Thus the capacity for two contraries can belong to a thing at the same time, but the contraries cannot belong at the same time; i.e., the actualities, e.g. health and disease, cannot belong to a thing at the same time. Therefore one of them must be the good; but the potentiality may equally well be both or neither. Therefore the actuality is better.

Also in the case of evils the end or actuality must be worse than the potentiality; for that which is capable is capable alike of both contraries.

Clearly, then, evil does not exist apart from things ; for evil is by nature posterior to potentiality.33 [20] Nor is there in things which are original and eternal any evil or error, or anything which has been destroyed—for destruction is an evil.

Geometrical constructions, too, are discovered by an actualization, because it is by dividing that we discover them. If the division were already done, they would be obvious; but as it is the division is only there potentially. Why is the sum of the interior angles of a triangle equal to two right angles? Because the angles about one point <in a straight line> are equal to two right angles. If the line parallel to the side had been already drawn, the answer would have been obvious at sight.34Why is the angle in a semicircle always a right angle? If three lines are equal, the two forming the base, and the one set upright from the middle of the base, the answer is obvious to one who knows the former proposition.35 Thus it is evident that the potential constructions are discovered by being actualized. The reason for this is that the actualization is an act of thinking. Thus potentiality comes from actuality (and therefore it is by constructive action that we acquire knowledge). <But this is true only in the abstract>, for the individual actuality is posterior in generation to its potentiality.36

The terms “being” and “not-being” are used not only with reference to the types of predication, and to the potentiality or actuality, or non-potentiality and non-actuality, of these types, [1051b] [1] but also (in the strictest sense37) to denote truth and falsity. This depends, in the case of the objects, upon their being united or divided; so that he who thinks that what is divided is divided, or that what is united is united, is right; while he whose thought is contrary to the real condition of the objects is in error. Then when do what we call truth and falsity exist or not exist? We must consider what we mean by these terms.

It is not because we are right in thinking that you are white that you are white; it is because you are white that we are right in saying so. Now if whereas some things are always united and cannot be divided, and others are always divided and cannot be united, others again admit of both contrary states, then “to be” is to be united, i.e. a unity; and “not to be” is to be not united, but a plurality.Therefore as regards the class of things which admit of both contrary states, the same opinion or the same statement comes to be false and true, and it is possible at one time to be right and at another wrong; but as regards things which cannot be otherwise the same opinion is not sometimes true and sometimes false, but the same opinions are always true or always false.

But with regard to incomposite things, what is being or not-being, and truths or falsity? Such a thing is not composite, so as to be when it is united and not to be when it is divided, [20] like the proposition that “the wood is white,” or “the diagonal is incommensurable”; nor will truth and falsity apply in the same way to these cases as to the previous ones.In point of fact, just as truth is not the same in these cases, so neither is being. Truth and falsity are as follows: contact38 and assertion are truth (for assertion is not the same as affirmation), and ignorance is non-contact. I say ignorance, because it is impossible to be deceived with respect to what a thing is, except accidentally39;and the same applies to incomposite substances, for it is impossible to be deceived about them. And they all exist actually, not potentially; otherwise they would be generated and destroyed; but as it is, Being itself is not generated (nor destroyed); if it were, it would be generated out of something. With respect, then, to all things which are essences and actual, there is no question of being mistaken, but only of thinking or not thinking them.Inquiry as to what they are takes the form of inquiring whether they are of such-and-such a nature or not.

As for being in the sense of truth, and not-being in the sense of falsity, a unity is true if the terms are combined, and if they are not combined it is false. Again, if the unity exists, it exists in a particular way, and if it does not exist in that way, it does not exist at all. [1052a] [1] Truth means to think these objects, and there is no falsity or deception, but only ignorance—not, however, ignorance such as blindness is; for blindness is like a total absence of the power of thinking. And it is obvious that with regard to immovable things also, if one assumes that there are immovable things, there is no deception in respect of time.E.g., if we suppose that the triangle is immutable, we shall not suppose that it sometimes contains two right angles and sometimes does not, for this would imply that it changes; but we may suppose that one thing has a certain property and another has not; e.g., that no even number is a prime, or that some are primes and others are not. But about a single number we cannot be mistaken even in this way, for we can no longer suppose that one instance is of such a nature, and another not, but whether we are right or wrong, the fact is always the same.

1 Aristot. Met. 7.1.

2 Cf. Aristot. Met. 6.2.1.

3 Chs. 6-10.

4 Aristot. Met. 5.12.

5 Cf. Aristot. Met. 5.12.11.

6 Cf. Aristot. Met. 5.22.

7 Cf. Aristot. Met. 10.4.7.

8 Literally “of the other,” i.e. the positive term.

9 The meaning of this awkward sentence is clearly shown in the latter part of 4.

10 Founded by Euclides of Megara, an enthusiastic admirer of Socrates. The Megarics adopted the Eleatic system and developed it along dialectical lines.

11 i.e. the form of “house.”

12 Cf. IV. v., vi.

13 i.e., we have just said that that which is incapable is deprived of its potency—in this case, of its potency for happening.

14 If it is true to say that a thing which is possible will not be, anything may be possible, and nothing impossible.

15 Cf. Aristot. Met. 9.8.6, 7.

16 Cf. Aristot. Met. 9.2.4, 5.

17 sc., if every potency must act automatically whenever agent and patient meet.

18 For Aristotle's views about infinity and void see Aristot. Physics 3.4-8, 4.6-9 respectively.

19 This is inconsistent with Aristotle's doctrine that the semen is the formal element in reproduction. Cf. Aristot. Met. 8.4.5, Aristot. Met. 6.9.5.

20 This is inconsistent with Aristotle's doctrine that the semen is the formal element in reproduction. Cf. Aristot. Met. 8.4.5, Aristot. Met. 9.6.5.

21 Cf. Aristot. Met. 7.7.10-12.

22 Aristot. Met. 5.11.

23 Cf. Aristot. Met. 5.4.1.

24 Aristot. Met. 7.7, 8.

25 Aristot. Physics, 6.6.

26 Probably a “trick” picture of some kind. So Pauson is said to have painted a picture of a horse galloping which when inverted showed the horse rolling on its back. Cf. Aelian, Var. Hist. 14.15; Lucian, Demosth. Enc. 24; Plut. Moralia, 396e; Pfuhl, Malerei und Zeichnung der Griechen, 763.

27 Cf. 19.

28 e.g. Empedocles; cf. Aristot. Met. 5.23.3 n.

29 Cf. Aristot. De Gen. et Corr. 337a 1-7.

30 Aristot. Met. 9.5.2.

31 For this description of the Platonists cf. Aristot. Met. 1.6.7.

32 This is a passing thrust at the Ideal theory. “Absolute knowledge” (the faculty of knowledge) will be a mere potentiality, and therefore substantially posterior to its actualization in particular instances.

33 The argument is presumably as follows (the fallacy, as pointed out by Bonitz, is indicated in parenthesis): That which has a separate substantial existence is actuality. Actuality is prior (substantially) to potentiality. Potentiality is prior to evil (in the moral scale. But since by evil Aristotle means the actualization of a potentiality for evil, potentiality is substantially posterior to evil). Therefore that which has a separate substantial existence is prior to evil; i.e., evil does not exist apart from particular instances of evil. The argument is directed against the Platonic Idea of evil (Plat. Rep. 476a); and the corollary which follows against the identification of Evil with one of the principles of the universe (Aristot. Met. 1.6.10, Aristot. Met. 12.10.6, Aristot. Met. 14.4.10, 11; cf. Plat. Laws 896e, Plat. Laws 898c).

34 The figure, construction and proof are as follows: * 35 Aristotle implies a proof something after this fashion: FIGURE BAC is an angle in a semicircle. From D, the mid-point of the diameter BC, draw a perpendicular DE to meet the circumference at E. Join EB, EC.*

36 This whole passage (sects. 4, 5) should be compared with Aristot. Met. 9.8.3-7, where it logically belongs.

37 This appears to contradict Aristot. Met. 6.4.3. But it is just possible to interpret κυριώτατα(with Jaeger) as “in the commonest sense.”

38 i.e. direct and accurate apprehension.

39 i.e. we cannot be mistaken with regard to a simple term X. We either apprehend it or not. Mistake arises when we either predicate something wrongly of X, or analyze X wrongly.