Aristotle · a new plain-English translation from the original language
1| Concerning that which is primarily, and to which all the other categories of being are referred, we have spoken — that is, concerning substance (for it is in accordance with the account of substance that the other things that are said to be are spoken of, both quantity and quality and the rest of what is so called: for all of them will have the account of substance, as we said in the first discussions). But since being is spoken of in one way as a this, or a quality, or a quantity, and in another way in accordance with potentiality and actuality, and in accordance with function, let us also draw distinctions concerning potentiality and actuality, and first concerning potentiality in the sense in which it is spoken of most properly, though this is not in fact the most useful sense for our present purpose: [1046a] for potentiality and actuality extend further than the things that are so called only in respect of motion. But once we have spoken of this sense, we will make clear the others too in the distinctions concerning actuality. That potentiality and being capable are spoken of in many ways has been distinguished by us elsewhere; of these, let those potentialities that are spoken of merely homonymously be set aside (for some are so called by a certain likeness, just as in geometry we speak of things as possible and impossible by their being or not being in a certain way); but as for those that bear on the same form, all of these are certain principles, and are spoken of with reference to one primary sense, which is a principle of change in another thing, or in the thing itself insofar as it is another.
2| For one kind is the potentiality of being affected — the principle, in the very thing affected, of a passive change brought about by another thing, or by the thing itself insofar as it is another; another kind is the state of not being affected for the worse, and of not being destroyed by another thing, or by the thing itself insofar as it is another, through some principle of change. For in all these definitions there is present the account of the primary potentiality. Again, these are called potentialities either of merely acting or of being acted on, or of doing so well, so that in the accounts of these there are also present, in a way, the accounts of the prior potentialities. It is clear, then, that in one sense there is a single potentiality of acting and being acted on (for a thing is capable both by having in itself a potentiality of being acted on, and by another thing's being acted on by it), but in another sense they are different. For the one is in the thing acted on (for because it has a certain principle, and because the matter too is a certain principle, the thing acted on is acted on, and one thing is acted on by another: for what is greasy is combustible, while what yields in such-and-such a way is crushable, and likewise in the other cases too), while the other is in the thing that acts, as heat and the art of building are: the one in what is capable of heating, the other in what is capable of building.
3| Hence, insofar as a thing is naturally united with itself, it is not acted on at all by itself: for it is one thing and not another. And incapacity and the incapable are the privation contrary to a potentiality of this kind, so that every potentiality is a potentiality of the same thing and in the same respect as some incapacity is an incapacity of it. Privation is spoken of in many ways: for we speak of privation both of what does not have something, and of what would naturally have it but does not have it — either altogether, or at the time it would naturally have it, and either in this or that way, for instance completely, or in however small a degree. And in some cases, if things that would naturally have something do not have it by force, we say that they have been deprived of it. Since some principles of this kind are present in things without soul, while others are present in things with soul, and in soul, and in the part of the soul that has reason,
4| [1046b] it is clear that some of the potentialities too will be non-rational and others will be accompanied by reason. That is why all the crafts, and the productive sciences, are potentialities: for they are principles of change in another thing, or in the thing itself insofar as it is another. And all the potentialities accompanied by reason are the same potentiality for contrary things, whereas the non-rational ones are each a single potentiality for a single effect — for instance the hot is a potentiality only of heating, but the medical art is a potentiality of disease and of health. The reason is that knowledge is a rational account, and the same account makes clear both the thing and its privation, though not in the same way, and is in a sense an account of both, but is more properly an account of the thing that is present; so that such sciences too must be sciences of contraries, but of one contrary in their own right and of the other not in their own right: for the account too is of the one thing in its own right, and of the other in a certain way accidentally; for it makes the contrary clear by way of denial and removal. For the primary privation is the contrary, and this is the removal of the other. And since contraries do not come to be present in the same thing at the same time, while knowledge is a potentiality by virtue of having reason, and the soul has a principle of motion, what is conducive to health produces only health, and what is capable of heating produces heat, and what is capable of cooling produces cold, but the person who has knowledge produces both.
5| For there is a rational account of both, though not in the same way, and this is present in a soul that has a principle of motion; so that the two are joined, by that principle, into motion toward the same end, from the same starting point — which is why the potentialities that go with reason produce the contraries of what the potentialities without reason produce: for they are encompassed by a single principle, the rational account. It is also clear that the potentiality for doing something well follows upon the potentiality for merely doing or being affected, but the latter does not always follow upon the former: for the one who does something well must also do it, but the one who merely does it need not also do it well. There are some, the Megarians for instance, who say that a thing is capable only when it is active, and when it is not active it is not capable — for instance, that a person who is not building a house is not capable of building, but only the person who is building a house, when he is building it; and similarly in the other cases. It is not hard to see the absurd consequences that follow for them. For it is clear that a person will not be a builder if he is not building a house (for being a builder just is being capable of building a house), and likewise with the other crafts. If, then, it is impossible to possess crafts of this kind without ever having learned and acquired them,
6| [1047a] and not have it without at some point losing it (whether through forgetting, or through some affection, or through time — for it is certainly not that the thing itself has perished, since it always exists) — then whenever he stops, he will not have the craft, yet how will he immediately build again, having somehow got it back? And the same holds for inanimate things too: for nothing will be cold or hot or sweet or perceptible at all, if no one is perceiving it; so it will follow that they are committed to saying Protagoras' account. But indeed nothing will even have perception if it is not perceiving or engaged in activity. If then that which lacks sight is blind, though naturally fitted for sight both when it is naturally fitted for it and while it still exists, the same people will be blind many times a day, and deaf too. Again, if what is deprived of a capacity is incapable, then what does not come to be will be incapable of coming to be; and whoever says that what is incapable of coming to be either is or will be will speak falsely (for that is what "incapable" meant), so that these accounts do away with both motion and coming-to-be. For what is standing will always be standing, and what is sitting will always be sitting: for it will not get up if it is sitting, since it will be impossible for it to get up, given that it is not capable of getting up. If then it is not possible to say these things, it is clear that potentiality and actuality are different things (whereas those accounts make potentiality and actuality the same, which is why they are trying to do away with something not insignificant), so that it is possible for a thing to be capable of being and yet not be, and to be capable of not being and yet be, and likewise with the other categories too: capable of walking and yet not walking, and capable of not walking and yet walking.
7| A thing is capable of this: that if the actuality of what it is said to have the potentiality for comes to belong to it, nothing impossible will result. I mean, for example, if a thing is capable of sitting and it is possible for it to sit, then if sitting comes to belong to it, nothing impossible will result; and likewise if it is capable of being moved or moving, standing or making stand, being or coming to be, not being or not coming to be. The word "actuality," which is put together with reference to "realization," has come into use, and has been extended to other things mainly from motions: for actuality seems to be motion above all, which is why people do not attribute being moved to things that do not exist, though they do attribute certain other predicates to them — for instance, that the things that do not exist are objects of thought and objects of desire, but not things in motion — and this is because, although they do not exist actually, they will exist actually.
8| [1047b] For among things that do not exist, some exist potentially; but they do not exist, because they do not exist in realization. If what has been said is what the possible is, or follows from it, it is clear that it cannot be true to say that this is possible but will not be, in such a way that impossible things thereby escape notice. I mean, for example, if someone were to say that it is possible for the diameter to be measured but that it will nevertheless not be measured — someone who does not reckon this to be impossible — on the ground that nothing prevents a thing that is capable of being or coming to be from not being and not going to be. But this must necessarily follow from what has been laid down: that even if we were to suppose that what is not, but is possible, is or has come to be, nothing impossible would result; yet it will result, for the measuring is impossible. For the false and the impossible are not the same thing: that you are now standing is false, but not impossible. At the same time it is also clear that if, A being the case, B is necessarily the case, then, A being possible, B too must be possible; for if it is not necessary that B be possible, nothing prevents its not being possible. Let A, then, be possible. Then, when A is possible to be, if A were posited, nothing impossible would result;
9| but B would necessarily be the case. But suppose this was impossible. Let it, then, be impossible. If, then, it is necessary that B be impossible, it is also necessary that A be impossible. But the first was impossible; therefore the second is impossible too. If, then, A is possible, B too will be possible, provided that things stood so that if A is the case, B is necessarily the case. If, then, though A and B stand thus, B is not possible in this way, neither will A and B stand as was assumed; and if, when A is possible, B is necessarily possible, then if A is the case, B must also be the case. For "it is possible that B necessarily is, if A is possible" signifies this: that if A is, and at the time and in the way in which it was possible for it to be, then B too must be, at that time and in that way. Since of all capacities some are innate, like the senses, some come by habituation, like the capacity for flute-playing, and some come by learning, like the capacities belonging to the crafts — those that come by habituation and reason one must have exercised beforehand in order to have them, but those that are not of this kind, and those that concern being acted upon, need not have been exercised beforehand.
10| [1048a] Since what is capable is capable of something, and at some time, and in some way, and of whatever else must necessarily be included in the definition, and since some things are capable of causing motion in accordance with reason, and their capacities involve reason, while other things are non-rational and their capacities are non-rational, and the former must necessarily be present in something ensouled while the latter are present in both — in the case of capacities of this latter kind, whenever agent and patient come into contact in the way they are capable of, it is necessary that the one act and the other be acted upon, but with the former this is not necessary: for all of these are each a single capacity productive of a single effect, whereas the rational capacities are capacities for contraries, so that they would produce contraries at the same time; but this is impossible. There must, then, be something else that has control; I mean by this desire or choice. For whichever of the two it desires in the controlling sense, this it will do, whenever it is present as it is capable of being present and comes into contact with what can be acted upon; so that everything that is capable in accordance with reason must, whenever it desires that for which it has the capacity, and in the way it has it, do this; and it has the capacity to do it when the patient is present and is disposed in a certain way; if not, it will not be able to act (for there is no further need to add the qualification "if nothing external prevents it"; for it has the capacity in the way in which the capacity is a capacity for acting, and this it is not in every case but when things are disposed in a certain way, among which the external hindrances will also be ruled out;
11| for these are excluded by some of the conditions present in the definition) — that is why, even if it wishes or desires to do two things, or contrary things, at the same time, it will not do them; for it does not have the capacity for them in that way, nor is the capacity a capacity for doing them at the same time, since it will act in the way appropriate to the things whose capacity it is. Since we have spoken of the capacity spoken of in relation to motion, let us determine, concerning actuality, what actuality is and what sort of thing it is. For as we distinguish these things, it will at the same time become clear about what is potential too, that we call potential not only what is naturally such as to move something else, or be moved by something else, either without qualification or in some particular way, but also in another sense — which is why, in our inquiry, we went through these points as well. Actuality, then, is the thing's existing, but not in the way we mean when we speak of it as existing potentially. We speak of something as potential, for example, when we say that there is a Hermes in the wood, or the half in the whole line, because it could be taken out, and we speak of someone as knowing even when he is not contemplating, if he is capable of contemplating; and the other case is actual. What we mean is clear in particular cases by induction, and one need not look for a definition of everything, but grasp the analogy as well: that as that which is building is to that which is capable of building,
12| [1048b] and the waking as against the sleeping, and the seeing as against that which has sight but has its eyes shut, and that which has been marked off from matter as against the matter, and that which has been worked up as against the unworked. Let one member of this differentiation be defined as the actuality, and the other as the potential. But things are not all said to be actual in the same way, but only by analogy — as this is in this or relative to this, so that is in that or relative to that; for some are as motion to potentiality, others as substance to some matter. But the infinite and the void, and other such things, are said to be potential and actual in a different sense from most existing things — for instance, from the seeing thing and the walking thing and the thing seen. For of these it is possible for the statement to be simply true at some time as well (the thing seen is true because it is being seen, the other because it is capable of being seen); but the infinite is not potential in this sense, as though it would at some time exist actually as separate, but only for knowledge. For the fact that the division never gives out is what accounts for this activity's existing potentially, though not for its being separated off. And since of actions which have a limit none is an end but all belong to what is around the end — for instance the making-thin, or thinning itself, and the things themselves, when someone is making them thin, are in motion in this way, without the things for the sake of which the motion occurs yet being present — these are not action, or at least not complete action (for it is not an end);
13| but that is action in which the end is also present. For instance, one is at the same time seeing and has seen, is understanding and has understood, is thinking and has thought — but one is not at the same time learning and has learned, nor being healed and has been healed. But one is living well and has lived well at the same time, and is happy and has been happy. If this were not so, the activity would have had to stop at some point, as when one is making something thin; but as it is, it does not, but one lives and has lived. Of these, then, we must call some motions, others actualities. For every motion is incomplete — thinning, learning, walking, building; these indeed are motions, and incomplete ones. For one is not at the same time walking and has walked, nor building and has built, nor coming to be and has come to be, or being moved and has been moved, but they are different things, and one is moving something and has moved it; but one has seen and is seeing the same thing at the same time, and is thinking and has thought. This sort of thing, then, I call an actuality, and that sort a motion. What actuality is, then, and of what kind, let this and the like make clear to us. But when each thing is potential and when it is not must be determined; for it is not at just any time whatever.
14| [1049a] For instance, is earth potentially a man? Or rather is it not, but rather when it has already become a seed — and perhaps not even then? Just as, then, not everything could be made healthy by the medical art, nor by chance, but there is something that is capable of it, and this is what is potentially healthy — the boundary for that which comes to be in actuality from thought out of what exists potentially is this: when, the person having willed it, it comes about with nothing external hindering; and there, in the case of what is being made healthy, when nothing among the things in it hinders. Similarly too a house is potential: if nothing among the things in this — that is, in the matter — hinders it from becoming a house, and there is nothing that needs to be added or taken away or changed, this is potentially a house; and likewise in the other cases, of all things whose principle of coming-to-be is external. And of all things whose principle is in the very thing that has it, they are potential whenever, with nothing external impeding, they will come about through themselves; for instance, the seed is not yet potentially a man (for it must still fall into something else and change), but when already through its own principle it is of such a kind, then it is already potential; but that former state needs another principle, just as earth is not yet potentially a statue (for it will become bronze only by changing). What we call a thing seems not to be this but rather to be made-of-that — for instance the chest is not wood but wooden, nor is wood earth but earthen; and again earth, if it is similarly not something else but made-of-that — that other thing is always, without qualification, the potentiality of what comes after it.
15| For instance, the chest is not earthen nor earth but wooden; for this is potentially a chest, and this is the matter of a chest — the matter of a chest without qualification being wood without qualification, but the matter of this particular chest being this particular wood. But if there is some first thing which is no longer called, in terms of something else, made-of-that, this is prime matter; for instance, if earth is airy, and air is not fire but fiery, fire is prime matter, not being a this. For the substrate and the attribute differ in this respect, in being a this or not being one; for instance, the substrate of the affections is a man, and body and soul, while the affection is the musical and the white (and when musicality has come to be present in it, it is called not musicality but musical, and the man is not whiteness but white, nor is it walking or motion but walking or being moved, in the way the made-of-that was said). Whenever, then, it is like this, the ultimate substrate is substance; but whenever it is not like this, but what is predicated is some form and a this, the ultimate substrate is matter and material substance. And it is right, then, that the made-of-that designation should be used in accordance with the matter and the affections,
16| [1049b] for both are indeterminate. When, then, one should speak of something as potential and when not has been stated. And since it has been previously determined in how many ways the prior is spoken of, it is clear that actuality is prior to potentiality. And I mean by potentiality not only the definite kind which is called a principle of change in another thing, or in the thing itself qua other, but in general every principle of motion or of rest. For nature too falls into the same class; for it is in the same genus as potentiality, since it is a principle of motion — though not in another thing, but in the thing itself qua itself. Actuality, then, is prior to every such potentiality, both in account and in substance; but in time it both is and is not prior in a way. That it is prior in account is clear (for it is because the thing that is capable in the primary sense admits of being actualized that it is called capable — I mean, for instance, capable of building is that which is capable of building, and capable of seeing is that which can see, and visible is that which is capable of being seen; and the same account holds in the other cases too, so that the account and the knowledge of the actuality must exist before the knowledge of the potentiality). But it is prior in time in the following way: the thing that is actual and is the same in form, though not in number, is prior. I mean this: prior in time to this man who already exists in actuality, and to the grain, and to the seeing thing, are the matter and the seed and the thing capable of sight, which are potentially a man and grain and a seeing thing, but not yet actually so;
17| but prior in time to these are other things which exist in actuality, from which these came to be; for always out of that which exists potentially there comes to be that which exists actually, through the agency of something that exists in actuality — for instance man from man, the musical man by the agency of a musical man — some first mover always being present; and the mover already exists in actuality. It has been said in the discussions concerning substance that everything that comes to be comes to be something out of something and by the agency of something, and that this agent is the same in form as the product. This is why it is also thought to be impossible to be a builder without having built anything, or a lyre-player without ever having played the lyre; for one who is learning to play the lyre learns to play it by playing it, and likewise in the other cases too. From this arose the sophistical refutation, that one who does not possess the knowledge will do that of which there is knowledge; for the one learning does not possess it. But because, of that which is coming to be, something has come to be, and of that which is in motion generally, something has been moved (this is clear in the discussions concerning motion),
18| [1050a] and the one learning must presumably already possess some part of the knowledge. But at any rate it is clear in this way too that actuality is prior to potentiality, both in coming-to-be and in time. But it is prior in substance as well, first because the things that are later in coming-to-be are prior in form and in substance (for example, a man is prior to a boy, and a human being is prior to seed: for the one already has the form, the other does not), and because everything that comes to be moves toward a principle, that is, an end (for the principle is that for the sake of which, and coming-to-be is for the sake of the end), and the end is actuality, 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; and likewise people have the art of building in order to build, and the capacity for theoretical study in order to study; but they do not study in order to have the capacity for theoretical study, except those who are practicing — and these are not really studying, but only in a certain way, or because they have no need to study. Further, matter exists potentially because it might come to be in the form; but when it exists actually, then it is in the form. And likewise too in the other cases, including those whose end is motion; hence, just as teachers think they have delivered their end when they have shown the pupil in action, so too does nature.
19| For if it did not come about in this way, there would be a Hermes of Pauson: for it would be unclear whether the knowledge is inside or outside, just as with that Hermes. For the work is an end, and the actuality is the work; that is why the name 'actuality' is derived from 'work,' and it points toward 'realization.' Now since in some cases the ultimate thing is the use — for example, seeing is the use of sight, and nothing else comes to be from sight besides this — while in other cases something does come to be from it — for example, a house comes to be from the art of building, besides the act of building — nonetheless in the one case it is the end, and in the other it is more the end than the potentiality is: for the building is in the thing being built, and it comes to be and exists together with the house. So wherever what comes to be is something other than the use, in these cases the actuality is present in the thing being made — for example, building is in the thing being built, and weaving is in the thing being woven, and likewise in the other cases, and in general motion is in the thing being moved — but wherever there is no other product besides the actuality, in these cases the actuality is present in the agents themselves — for example, seeing is in the one seeing, and contemplation is in the one contemplating, and life is in the soul, and hence so too is happiness, for
20| [1050b] happiness is a certain kind of life. So it is clear that substance and form are actuality. By this argument, then, it is clear that actuality is prior in substance to potentiality; and, as we said, in time one actuality always precedes another, all the way back to the actuality of that which first and always causes motion. But it is prior also in a more authoritative sense: for things that are eternal are prior in substance to things that are perishable, and nothing eternal exists potentially. The argument is this: every potentiality is at the same time a potentiality for the contradictory. For what is not capable of belonging could not belong to anything, but everything that is capable admits of not being actual. So what is capable of being admits both of being and of not being; the same thing, then, is capable both of being and of not being. But what is capable of not being admits of not being; and what admits of not being is perishable, either without qualification, or in the very respect in which it is said to admit of not being — either in place, or in quantity, or in quality; and without qualification means with respect to substance. Nothing, then, that is imperishable exists potentially without qualification (though nothing prevents it from existing potentially in some respect, for example in quality or in place); all such things, then, exist actually. Nor do the things that exist of necessity exist potentially (and yet these are primary:
21| for if these did not exist, nothing would exist); nor does motion, if any motion is eternal; nor, if anything that is eternal is in motion, does it move in virtue of a potentiality, except with respect to 'from where to where' (and nothing prevents there being matter for this). That is why the sun and the stars and the whole heaven are always in actuality, and there is no fear that they will ever stop — the fear that the natural philosophers have. Nor do they grow weary in doing this: for the motion involved for them does not concern a potentiality for the contradictory, as it does for perishable things, such that the continuity of the motion would be a strain; for it is the substance, being matter and potentiality and not actuality, that is responsible for this strain. The perishable things imitate the imperishable, even those that are involved in change, for example earth and fire. For these too are always in actuality: for they have their motion in their own right and in themselves. But the other potentialities, as we have distinguished them, are all potentialities for the contradictory: for what is capable of moving in this way is also capable of moving not in this way, at least those that accord with reason; while the non-rational potentialities will be potentialities for the contradictory only by being present or absent. If, then, there are certain natures or substances of the sort that those who speak of the Forms describe in their arguments, something would be far more a knower than knowledge itself is, and something more in motion than motion is:
22| [1051a] for these would be actualities rather, while those Forms are potentialities relative to them. It is clear, then, that actuality is prior both to potentiality and to every principle of change. But that it is also better and more honorable than a good potentiality is clear from the following. For whatever is spoken of in terms of being capable, the same thing is capable of the contraries; for example, what is called capable of being healthy is the same thing as what is capable of being sick, and at the same time: for the same potentiality is a potentiality for being healthy and for being ill, for being at rest and for being in motion, for building and for tearing down, and for being built and for collapsing. So the capacity for contraries belongs to a thing at the same time; but the contraries themselves cannot belong to it at the same time, and the actualities too cannot belong to it at the same time (for example, being healthy and being ill), so that one of these two must be the good, whereas the potentiality is alike a potentiality for both, or for neither: the actuality, then, is better. And in the case of bad things too, the end and the actuality must necessarily be worse than the potentiality: for what is capable of both is the same for both contraries. It is clear, then, that the bad does not exist apart from actual things; for by nature the bad is posterior to the potentiality. So neither in the things that exist from the beginning, that is, the eternal things, is there anything that is either bad, or erroneous, or corrupted (for corruption too is one of the bad things).
23| Geometrical diagrams too are found by an activity: for it is by dividing that people find them. If they were already divided, the result would be obvious; as it is, it is present only potentially. Why does the triangle have angles equal to two right angles? Because the angles about a single point are equal to two right angles. So if the line parallel to the side had been drawn, it would have been immediately obvious to anyone looking at it, why this is so. Why is the angle in a semicircle universally a right angle? If three lines are equal — the two forming the base and the one set up from the midpoint — it is obvious to one who looks at it, provided he knows that fact. So it is clear that the things that exist potentially are discovered by being brought into actuality: and the reason is that thinking is an actuality; so that the potentiality comes from the actuality, and this is why people come to know by making (for the actuality that is numerically distinct is posterior in coming-to-be). Since being, and not-being, are spoken of in one sense with reference to the figures of the categories, and in another sense with reference to the potentiality or actuality of these or their contraries,
24| [1051b] while being in the most authoritative sense is being true or false — and this, in the case of things, consists in their being combined or separated, so that he who thinks the separated to be separated and the combined to be combined speaks truly, while he whose thought is contrary to how the things actually are is in error — when, then, does what is called true or false exist, or not exist? For we must consider what we mean by this. For it is not because we think truly that you are white that you are white; rather, it is because you are white that we, in saying this, speak truly. If, then, some things are always combined and incapable of being separated, while others are always separated and incapable of being combined, and others admit of the contraries, then to be is to be combined and to be one, and not to be is not to be combined but to be more than one: so, concerning things that admit of being otherwise, the same opinion and the same statement come to be both false and true, and it is possible at one time to speak truly and at another time to speak falsely; but concerning things incapable of being otherwise, it is not the case that they are at one time true and at another time false, but the same things are always true or always false. But concerning things that are without composition, what is it for them to be or not to be, and what is the true and the false?
25| For it is not composite, so that it would exist when put together and not exist when it is divided, as the white wood is, or the incommensurable diagonal; nor will the true and the false still hold in the same way for those things either. Rather, just as the true is not the same in these cases, so too being is not the same; instead, one thing is true or false in this way: touching and asserting is true (for affirmation and assertion are not the same thing), while not touching is failing to know (for it is not possible to be deceived about what a thing is, except accidentally; and the same holds for the non-composite substances too, for it is not possible to be deceived about them: and they all exist actually, not potentially, for otherwise they would come to be and perish, but as it is, being itself does not come to be nor perish, for it would have to come to be out of something: so about whatever things are precisely what it is to be something, and are actualities, it is not possible to be deceived, but only to think them or not; rather, what is sought about them is what they are, whether they are of such a kind or not): but being in the sense of the true, and not-being in the sense of the false, is one thing, if it is composite, true, and if it is not composite, false.
26| And the one, if indeed it is, is so in this way, and if it is not so, it is not. [1052a] And the true is thinking these things; but the false does not exist, nor does deception, but only ignorance — not the kind of ignorance that is like blindness. For blindness is as it would be if someone had no capacity for thought at all. And it is clear too that about unchanging things there is no deception with respect to time, if one supposes them to be unchanging. For example, if someone thinks the triangle does not change, he will not think that it has two right angles at one time and not at another (for it would be changing), but rather that one thing holds and another does not — for example, that no even number is prime, or that some are prime and some are not; but about a single number not even this holds, for he will no longer think that some are so and some are not, but will state truly or falsely as though it always held so.