Primary Philosophy - Essay

Primary Philosophy

(Classical and Medieval Literature Criticism)

Franz Brentano (essay date 1862)

SOURCE: "Potential and Actual Being," in On the Several Senses of Being in Aristotle, by Franz Brentano, edited by Rolf George, translated by Rolf George, University of California Press, 1975, pp. 27-48.

[In the following essay, originally published in 1862, Brentano discusses the nature of potential and actual being as analyzed by Aristotle in Metaphysics. Brentano examines Aristotle's definitions of potential and actual being and presents readings of them designed to resolve some difficulties within them. Finally, he explores the relationship between the two concepts, maintaining that "movement is the actuality of the potentiality."]

The two senses of being …, namely, being which is divided into the categories and potential and actual being, belong together and are intimately connected with each other.1 Thus they have in common that the science of being, metaphysics, is concerned in the same way with one as with the other,2 while, as we saw, both accidental being and being in the sense of being true were excluded from it. Since being, as the most general, is asserted of everything,3 it follows for the subject of metaphysics that it comprises everything insofar as it has extramental being which is one with it and belongs to it essentially. Hence it follows that, just as the being which divides into the categories, being in the sense now under discussion is being that is independent and outside the mind [on kath' hauto exo tes dianoias].

l. The kind of being which is divided into actual [on energeia] and potential [on dynamei] is being in the sense in which this name is applied not only to that which is realized, that which exists, the really-being, but also to the mere real possibility of being.

Potential being [on dynamei] plays a large role in the philosophy of Aristotle, as does the concept of matter [hyle]. Indeed, these two concepts are coextensive,4 while actual being [on energeia] is either pure form or is actualized by form.

There is a great difference between what we here mean by the potential [the dynaton or dynamei on] and what in more recent times is meant by calling something possible in contrast with real, where the necessary is added as a third thing. This is a possibility which completely abstracts from the reality of that which is called possible, and merely claims that something could exist if its existence did not involve a contradiction. It does not exist in things but in the objective concepts and combinations of concepts of the thinking mind; it is a merely rational thing.

Aristotle was quite familiar with the concept of possibility so understood, as we can see from De interpretatione, but it bears no relation to what he calls potential being, since otherwise it would have to be excluded from the subject of metaphysics along with being as being true. So that no doubt may remain, he mentions in Met. [Metaphysics] V. 12, as well as in IX. 1, the impossible whose contrary is necessarily true [adynaton hou to enantion ex anankes alethes] (Met. V. 12. 1019b23). The possible object [dynaton] which is associated with this impossibility is distinguished from the potential object [dynaton] which bears this name because it stands in relation to a power [dynamis]. It is the same only in name5 and must be distinguished from this potentiality along with the powers of mathematics, a2, b3, etc., which are powers only in a metaphorical sense [kata metaphoran].6 Thus he speaks here of something which really has potential being. This is based upon his peculiar view that a non-real, something which has, properly speaking, non-being (me on)7, in a manner or speaking exists insofar as it is potentially, and it is this which leads him to a special wide sense of real being, which comprises as well that which potentially is.

Now, what is this potential thing which, being real, belongs to the object of metaphysics, and which has potential being as opposed to actual being? Aristotle defines it in the third chapter of the ninth book as follows: "a thing is possible if there is nothing impossible in its having the actuality of that of which it is said to have the potentiality."8 Two things are to be noted about this definition: (1) that Aristotle seems to define a thing through itself, since he defines the possible in terms of the impossible, and (2) the definition is based upon the concept of actuality whose understanding is therefore presupposed.

The first difficulty can be resolved as follows: the impossible [adynaton] in question is the contradictory. It is opposed to the possible in the logical sense which we have just discussed and not to the potential [dynaton] which we are now trying to comprehend.

The second difficulty forces us to direct our attention initially to actuality [energeia]. Potential being cannot be defined except with the aid of the concept of actuality, for the latter is prior in both concept and substance, as we are told in Met. IX. 8: "Actuality," he says, "is prior to potentiality both in concept and in essence." Further on he continues, "It is necessary that concept and cognition of the former precede that of the latter."9 "Actuality" [energeia, Wirklichkeit] derives from "to act" (ergo, wirken), a verb having to do with motion, since, as he says, it is especially motion which seems to be an actuality.10 But the extension of the concept does not stop here.11 What then is actuality? Aristotle does not give us a definition and declares explicitly that we should not demand one, since the concept of actuality is so basic and simple that it does not permit definition but can be clarified only inductively through examples.12 As one of these he adduces the knower, if we mean by this expression a person who is presently engaged in an act of cognition; hence, this person is actually cognizing. Furthermore, a statue of Hermes is actual if it is completely sculpted, finished, and not raw wood or a marble block to which the artist has not yet put his hand. If someone knows something but is not presently engaged in the act of cognition, or if a block is rough and unsculpted, then the former is not actually cognizing, even if he could perform the act of cognition, and the latter is not actually a statue, even if it is one potentially.13 Thus we see that we are led back to potential being; it is best to clarify the concept of actuality through the relation between actuality and potentiality. They are related "as that which is actually building to that which is capable of building, as that which is awake to that which is asleep, as that which is seeing to that which has eyes shut, but has the power of sight, and as that which is formed from matter is to matter, and as the finished article to the raw material. In this contrast let one member be assigned to actuality, the other to potentiality."14 We can see from this collection of examples that something is actual if it exists in complete reality; potential being lacks this reality, although "nothing impossible will result if potential being achieves the actuality of which it is said to be capable." (see above). Thus Aristotle often uses the designation "actuality" [energeia] and "entelechy" [entelecheia] interchangeably15 where the latter means the same as consummation (teleiotes),16 as was correctly noted by Alexander and Simplicus.17 But how? A mere potentiality in things, a merely potential thing which exists, is that not a thing which exists and yet does not have existence? Is this not a contradiction and impossibility? The Megarians did indeed see a contradiction here, as often happens if one withdraws the basis of being from contradictions which ought to be resolved. Thus they denied the merely potential, and that a thing is capable of something which is not already actual in the thing. But it is not difficult, says Aristotle,18 to reduce such an assertion to absurdity. For then there would not be a builder who is not presently engaged in building, and no one would have an enduring ability. But it is certain that a person who has exercised an art does not at once lose his knowledge and his capability, and that he does not have to learn and acquire them for every new use, and it is equally certain that the artist remains an artist, even if he rests from his activity. Furthermore, nothing would be cold or hot, and Protagoras would be correct in his claim that all truth depends upon subjective sensation and opinion.19 Furthermore, the man with healthy eyes and ears would often become blind and deaf during a day since, when he closes his eyes and ceases actually to see he would, on this theory, no longer see potentiality, i.e., he would have lost the very capacity to see.20 Finally, all coming to be and passing away of things would have become a complete impossibility, for everything would be what it can be, and what it cannot be it could never become, and whatever one might say of past and future things would be a lie.21

In this way, Aristotle rebuts the Megarians and clarifies for us the existence and justification of his potential being. The additional examples which he adduces in this context serve to remove all doubt about the meaning of "potential being." But perhaps it is possible to employ in addition a manner of illucidation which we have used above in the determination of accidental being [on kata symbebekos]. I have in mind the enumeration of the different kinds of potential being, or rather of the different ways in which various things participate in this name. This can be done since "potential being" is not used univocally, but applies to the concepts which fall under it merely with a certain unity of analogy. In Met. V. 12. four modes are indicated in which something can be called potential. They all agree in that they are origins of something,22 and all of them are reduced to a single principle from which they receive the name, and therein consists their analogy.23 The first mode of potentiality which Aristotle distinguishes is the origin of motion or change in another, insofar as it is another.24 The last clause is added on since the active principle could possibly be contained in the subject, as when something moves itself. Even then it is not moving and moved, active and passive, in one and the same respect; one and the same thing acts and receives action, but not insofar as it is the same, but insofar as it is another.25 The second mode is the passive capacity, which is the principle whereby something is moved by another insofar as it is another.26 Again, the last clause is added for similar reasons, since if something is passive with respect to itself, it is active not insofar as it is the same thing but insofar as it is another. The third mode of potentiality is impassivity [hexis apatheias], as he calls it in Met. IX. 1. 1046al 1. This is the disposition of a thing which makes it altogether incapable of suffering or change, or at least which makes it difficult for it to change for the worse. It is the so-called capacity of resisting.27 Finally, the fourth mode in which something is called a potentiality is the principle not just of doing or suffering something, but of doing it well and according to desire. Thus, for example, if somebody limps or stutters we do not describe him as one who can walk or talk; rather, we use these words for those who can do these things without stumbling and error. Similarly, green wood is called non-flammable, while dry wood is called flammable, etc.28

Corresponding to these four modes of potentiality, there are four kinds of things capable,29 which are most adequately described not as "possible" [moeglich] nor as "powerful" [maechtig], but rather as "capable" [vermoegend] or "able" [faehig]. All of these are called capable relative to a capacity [kata dynamin], which does not hold for the concept which logicians connect with the word "possible" [dynaton].30 As analogous concepts all of them can be reduced to the first mode of things capable and of potentiality, to the source of change in another insofar as it is another [arche metaboles en hetero he heteron], from which they also receive their name.31 It is a question whether the here-indicated modes of potentiality [dynamis] and of things capable [dynaton] will attain our purpose, which was to ascertain the various modes of potential being. Is it perhaps the case that our potential being [dynamei on] is one and the same as the thing capable [dynaton] which was just mentioned? We must deny this if we wish to retain the concept of potential being [dynamei on], which was introduced with sufficient clarity above. Both physics and metaphysics agree that the first principle of motion is to be sought in God, but God, though certainly a thing capable [dynaton], is in no way a potential being, since he is an actual being [on energeia] in the fullest sense of the word.32 Hence this kind of thing capable [dynaton], which occupies the third position in the above order, shows us that we should not seek the modes of potential being [dynamei on] in those of the things capable [dynaton]. But how? Is there only one mode of potential being [dynamei on] and is this the concept of a genus in which all things designated by that name participate in the same manner? What will be the method by which we gain knowledge of the various modes of potential being?

The third chapter of the ninth book speaks of a thing capable [dynaton]; the entire context and the examples themselves show clearly that in this case it is identical with potential being [dynamei on], and it is said that it is found in every category.33 The same holds, of course, also of actual being [on energeia]; thus the tenth chapter of the same book and the seventh chapter of the fifth claim that in every category some objects are said to be in actuality, others in potentiality.34 If this is so, then it is clear that potential as well as actual being is said in many ways and can be called one only by analogy. This is necessarily the case with everything that reaches beyond the extension of any one category, as Aristotle clearly indicates in Eth. Nic. [Nicomachean Ethics] 1.4. 1096al9 and other places. We, too, shall give a detailed demonstration of this point, and shall recognize the principles upon which it rests.35 Consequently, Aristotle also asserts explicitly of actual being that "not everything is said to have actual being in the same, but only in an analogous way: as one is in or to a second, so a third is in or to a fourth; for some are related as operation to potency, others as form to some sort of matter."36 And with respect to potential being [dynamei on] it is a major objection to Plato and the Platonists that they did not realize how every category presupposes as a different mode of being a certain determination and mode of potentiality.37 We have already touched upon the close relation between potential and actual and being which is divided into the categories,38 and we shall encounter a consequence of this fact, viz. the variegation of the concepts of potential as well as actual being. There are as many modes of potential being and actual being as there are categories; through the latter we shall understand the number of, and differences between, the former.

But something remains to be done for the complete determination of potential being [dynamei on]. The question is at what time is something potentially; the analogous question with respect to actual being does not occasion any doubts. It would certainly be incorrect to say of a newborn child that he is capable of speaking, of walking, or even of investigating the deepest principles of science. It is necessary that he should first grow in strength, that the germ of his talent should unfold so that he may acquire the ability, which he still lacks, to do all these things. Thus it is not correct to say that earth is a potential statue, for one cannot make such a statue of it until its nature has been changed, and it has become, for example, ore.39 But how, in general, can one determine when something is a potential being?

Anything which is potentially something else does not in reality become this thing except through the influence of an efficient cause. Thus to every potential being there corresponds a certain efficient cause and its activity, whether it be artificial, where the principle of realization is external to the potential being, or natural, where it resides within the latter. Anything has potential being if either nature or art can make it actual through a single action. It is potential through art if the artist can actualize it whenever he wants to, provided only that there is no external hindrance; thus, for example, something is called potentially healthy (curable) if it can become healthy through one application of medical art. Something is potential through nature if it can be lead to actuality by its peculiar active principle or its inherent natural power, provided only that no external hindrance stands in the way. In this manner, something is potentially healthy if there is nothing in the sick body which must be removed before nature can exercise her healing force. But wherever other changes are presupposed before the proper process of actualization can begin, there is no potential being. Trees which must first be felled and dressed, or the stuff which must first transform itself into a tree, these are not potentially a house; but when the beams from which it can be erected are finished, then one can say that the house has potential being. Thus the earth is not potentially a man, and even the semen is not, but if the foetus can become an actual man through its peculiar active principle, then it is already potentially a man.40

All this confirms anew the determinations given above of the concepts of actual being [on energeia] and potential being [on dynamei] so that there can be no further doubt about the sense which Aristotle connects with the word 'being' [on], insofar as he comprehends under it not only fully actualized, but also unactualized being, which is only potentially whatever it is, and strives toward and desires its form, as it were.41

2. Connections between states of potentiality and actuality. Movement [kinesis] as actuality which constitutes a thing as being in a state of potentiality.

In the previous section we have considered what Aristotle meant by actual being [on energeia] and potential being [on dynamis]. The latter appeared as being which was as such incomplete, and this is the reason why the perfect separate substance, God, does not in any way partake of potential being, but is pure actuality. On the other hand, if a thing is composed of substance and accident, matter and form, then this imperfection results in its not being free of potentiality; for such a thing actual being consists of a union of potential being with actuality.42 This is not inconsistent, as can be seen from the definition of potential being itself.

But aside from the what of potential and actual being we have also noted a when for both. For potential being we did so following Aristotle, while it is of itself clear that for actual being the state of its actualization through form must correspond to its completion. But while there is no doubt that this union of potential and actual being actually occurs, a union of the states which correspond to one or the other does not seem possible since the state corresponding to unactualized potential being is a state prior to actualization which, however, can be brought about through a single process of becoming.… Yet even their union is in a sense not inconsistent; of course, we do not here speak of a simultaneous union, for if a body is now potentially and later actually white, then this union in the subject is not properly called a union of states, and there are no problems with respect to this matter. A simultaneous union, however, is possible in this way: something which is actually ore is in a state of potentiality with respect to a certain figure, etc. This is a union no different from those occuring between something that has actual being with a second and a third thing which has actual being, as when one and the same subject is actually a body, actually large, actually green, etc. In this case, the actuality of that which actually is does not belong to the potential object as such; for example, the actuality of the ore belongs to the ore as ore but not as a potential statue.43 In the same manner we can explain the union of something actually alive with the potential corpse, etc. But there is a second manner in which both states can be united, and this occurs in the state of becoming, on kinesei, as Aristotle calls it.

In Met. XI. 9 he gives the following remarkable definition of motion [kinesis], which is not easily comprehensible in spite of everything he has already taught us about potentiality and actuality. He says this: "The actuality (energeia) of the potential (tou dynamei ontos) as such I call movement." Similarly, in the first chapter of Book III of the Physics: "Since being of every kind is divided into actual and potential being, the actuality (entelecheia) of potential being as such is motion." And farther down: "It is obvious that the actuality of what is potential as potential is movement."44

This definition makes it clear, first of all, that by potential being or the potential (dynamei on, dynaton), we are to understand that which is in a state of potentiality; for if we were to take it in the sense in which all matter as such, even after its union with form, is to be called something merely potential, then aside from the separate substances, every form would have to be called an actuality of a potential being, and nothing peculiar to movement would have been indicated.

But there is something else which causes problems: the words "the actuality of potential being" can be interpreted in two ways, as can be seen in the following: every form or actuality which is not a separate substance can be called an actuality of something in two ways: (1) as the actuality of the substratum, for example when we say of the soul that it is the actuality of the physical body which is potentially alive;45 and (2) as the actuality of the composite which was formed from matter through its union with form, for example when we say of the soul that it is the actuality of the living being. Since in our definition movement was described as the actuality of something, viz., of potential being, the question is whether this potential being is to be construed as subject or as something which is constituted through movement. Each interpretation, despite the difference, gives a true sense which agrees with what has been said so far, and which therefore ultimately coincides with the other. Let us show this by looking at both of them more closely. According to the first interpretation, which is adopted by most commentators,46 our definition would determine movement to be a form which has the following characteristics: as it brings its subject from the corresponding state of potentiality to [the] actuality [of movement], it leaves it in a state of potentiality to another thing. This other thing is such that the subject was in a state of potentiality to it by virtue of being in a state of potentiality to the actuality of the movement itself.

To understand this, we must remember what was said in the preceding section in answer to the question at what time something is a potential being. Something has potentiality if nature or art can make it an actuality through a single action, hence if it can be actualized through a single becoming. But this becoming, even if it must be single, does not have to be momentary. If a black body becomes white through a single change, it does not follow that it changes suddenly. Thus becoming and consummation do not coincide here; first the subject partakes in becoming, and then achieves its completion. Hence, here the subject has a double potentiality, viz. (1) to the becoming of the form, and (2) to the form itself. Yet this double state of potentiality is in itself and in its concept only a single one. For if a black body is capable of becoming white through a single becoming (hence as a potentiality to the becoming-of-the-form), it is obviously in a state of potentiality to whiteness. Now, if a subject is transferred from this state of potentiality to actuality with respect to becoming, then it is also transferred to a new and heightened state of potentiality with respect to the form which is the consummation of becoming.47 It is a heightened state insofar as the state of becoming is that from which the subject immediately achieves complete actuality, while the state before the state of becoming must first be changed into the state of becoming so that the subject may thereafter be transferred into a state of consummate actuality. Hence commentators have described this state as a third, intervening, state between mere potentiality and actuality;48 this state of an actual tendency after the act is being qua movement [on kinesei], while movement [kinesis] is that becoming which actualizes but does not completely exhaust potentiality.

Thus there are no further difficulties in understanding the definition. The kind of thing something is [he toiouton esti] distinguishes this kind of union between states of potentiality and actuality from the one mentioned above in which, for example, the actuality of the ore as ore coexisted with the potentiality of being a statue.49

The authority of almost all commentators speaks for this interpretation; yet, as mentioned above, there is still another possible interpretation which has its own advantages. The first interpretation made good sense with respect to movement [kinesis], yet it does not seem free of inaccuracies. For if the double potentiality of the subject were really only one, both in itself and according to the concept (haplos kai kata ton logon, Physics III. 1. 201a32), then it would be impossible for this state to be terminated with respect to one of them, and to continue with respect to the other. For if it is terminated with respect to whatever, then it is completely terminated, hence for both. And if only the becoming of the form has become actual, while the form itself is still potentiality, it has not remained in the previous, but in a new and more advanced state of potentiality, viz. precisely its state of becoming. Thus in a sense a subject has remained in a state of potentiality, just as I can say of something which is now white and then red that it has remained in a state of actuality with respect to color, although it is now colored by virtue of a different state of actuality than before; but in the strict sense the subject has not remained in a state of potentiality; rather, it has been transferred from one state of potentiality to a second state which aims at the same form, i.e., it is in a state of becoming, which is constituted by movement.

Thus, if the great authority of the men who maintained the first interpretation did not make me hesitate, I would unquestionably prefer the second, according to which the definition determines as follows: Movement is the actuality of the potential as such, just as the form of the ore is the actuality of the ore as such, i.e., it is the actuality (energeia) which makes something that is potentially (tou dynamei ontos) into that which it is (he toiouton esti), viz. into this potential being. In other words, it constitutes and forms a potential (it constitutes and forms something which is in a state of potentiality as being in this state). After what has been said, the definition when put this way has no further difficulties. This interpretation has the advantage that it makes the definition not only more precise, but also simpler. Let the following contribute to its comprehensibility, where we make constant reference to the appropriate passages in Aristotle to show that our argumentation agrees with his meaning. We shall show (1) that there are potentialities which are constituted as such through some actuality, (2) that this is not the case with all potential states, and (3) that where it is the case, the constituting actuality is a movement.

The first point is likely to provoke the most doubt and opposition, hence we want to treat it with special care. Thus we shall conduct our proof as follows: we shall show (1) that in many cases there are two different states of potentiality which are related to the same state of actuality; and (2) that, where there is such a multiplicity of potential states, at least one of them must be constituted (or formed) by some actuality. We begin by referring back to the previous section, in which we saw that aside from that which is in a state of actuality [the energeia on], there is also being in the state of potentiality [on dynamei].50 But in virtue of what is something constituted an actual being [on energeia]? Obviously, through a form or actuality. But what about a potential being? Is it, too, constituted (formed) as such by something? It is indeed difficult to believe that a state of potentiality as such can be constituted through a form, which is, after all, an actuality;51; yet this is the case, provided only that there is a double state of potentiality with respect to the same form, as we have just said.…

Let us again consider and confirm this fact. We have said that there is often a double state of potentiality with respect to the same actuality, and this was derived from another truth which was proved earlier (p. 37), viz. that there are double states of potentiality, i.e., that there are things which, by virtue of one and the same state (one and the same in itself and in concept (haplos kai kata ton logon), have potentiality to two different actualities. For example, something which is potentially white has potentiality for whiteness and also for becoming-white by virtue of one and the same state, since a single operation, namely white-making, actualizes both (see above). From this we have concluded that if both actualities could occur only one after the other, the first of them would have to terminate the state of potentiality with respect to the second, for the two states of potentiality are one and the same. But since the subject maintained the potentiality to the second form, it could do so only by virtue of a second, new state of potentiality to this form.… It follows from this that there are two states of potentiality corresponding to this actuality. Hence there is a double state of potentiality with respect to the same actuality.

We can support this argument by a second one. If there is a state of potentiality with respect to a form from which and by virtue of which the subject can immediately attain possession of actuality, and if there is a state of potentiality with respect to the same form, from which and by virtue of which the subject cannot immediately attain possession of actuality, then these two states are distinct and there is a double state of potentiality with respect to one and the same form. But the antecedent of this conditional proposition is true, hence also the consequent. For it is true that a stone which is thrown is capable (has potentiality) of reaching a certain location toward which it has been thrown, and that from the state in which it is now, viz. the state of a-thing-being-thrown, it immediately attains a state of rest having reached its target. And it is true that a stone which rests in a certain location is capable of attaining another location since it can get there through a single throw, and yet it cannot immediately get there from the state in which it is before the throw; it must first attain the state of being-thrown. Here we have an example of two states of potentiality with respect to the same actuality. We take this argument from Aristotle himself when he says, in the second book of the Metaphysics, that there is a double way in which something comes from something, as a man from a boy who matured to manhood, or the air from water; in the first case, that which is becoming changes into that which has become, out of that which is in the process of completion (actualization) there arises the completed (the actual). "For," he says, "there is always an intermediate: just as becoming is between being and non-being, so that which is becoming is between what is and what is not."52

We take a further confirmation of our claim from the same passage: that we have here two different states follows from the fact that there is a characteristic which is peculiar to one of them, but which the other lacks. Something can pass from a state of becoming into a state of actuality, but not vice versa; for what is already white cannot become white. But from the state of potentiality prior to becoming, a thing attains the state of actuality, and conversely; for the black is potentially white, and after it has actually become white, it is potentially black and can therefore return to this state.53

But wherever such a multiplicity of potential states is found, at least one must as such be constituted (formed) through an actuality. This is perfectly clear and certain. For privation as such does not constitute anything. It is itself only accidental being [on kata symbebekos] and, taken by itself, has no existence at all;54 while matter, as such, is undifferentiated, and since it receives all its determinations from the form through which it is what it is, there can be only one matter with respect to one and the same form.55 Hence, how could this matter produce the difference between the state of becoming and the state of the potentiality to the same form prior to becoming? Impossible! Rather, only one thing is possible, viz. that the difference between the two states of potentiality is produced by a form, so that at least one of the two states as such is constituted (formed) through an actuality. And this is what we had wanted to prove in the first place, and what at first sight is liable to occasion considerable doubt, i.e., that there are states of potentiality which are constituted as such through an actuality.

One can also show this in another way once the above established proposition has been secured, i.e., that one and the same state of potentiality (one and the same both in itself and in concept, see above p. 37) is a state of potentiality with respect to two actualities. For if the two actualities considered by themselves are two, then they must be one in their relation [in der Ordnung] to this state of potentiality, and so one of them must be a function of the other [zur andern hingeordnet sein], hence must give the subject an actual tendency toward itself, i.e., toward a new state of potentiality which is closer to it, an intermediate state between the first and actuality.56

Now we come to the second point. If the preceding investigation has made it clear that many things which are in a state of potentiality are constituted as such through a form, this is not to say that this must be the case with everything that is in a state of potentiality. On the contrary, this, too, would be an error; consequently, we find Aristotle opposing it in the third book of the Physics and the corresponding part of the eleventh book of the Metaphysics. Let us now give a somewhat more complete version of his argumentation. If something is in a state of potentiality, and is constituted as such by an actuality, then (1) it must be in a state of actuality, and (2) it must, as such, have a form, and therefore an essence and a concept which determines this form, for each form issues in an essence. From this it follows, for instance, that a motionless waxen ball, which is potentially a cube, is not constituted by an actuality as being in that particular state [of potentiality]. For, of all the forms which are in a wax ball, it can only be the actuality of the wax as wax, or the softness of the wax, which lend it a certain disposition that facilitates reshaping it. But when the wax ball has become a cube, the form of the wax as wax, hence also its softness, hence everything through which the wax was formerly constituted remains; now, if this were a state of potentiality, hence a state prior to actuality, then the cube which has come about would not yet be a cube, which is contradictory. Hence, one would have to believe that it is the form of the wax ball as a sphere which constitutes the potentiality of becoming a cube; for it is indeed true that whatever has the shape of a sphere cannot at the same time be a cube. But against this a second argument can be advanced which is also decisive with respect to the previously mentioned form of the wax. The wax ball is a potentiality not only to the form of the cube but to a thousand other shapes as well. Hence, all these states of potentiality would have to be constituted through the form of the ball (or the wax) if the wax ball as sphere (or as wax) were indeed presently in a state of potentiality, and hence they would have to be identical with the sphere (with the wax) as such (i.e., in themselves and in this essence and concept). But this is impossible; for if two are identical with the same third thing, then they are identical with each other, and hence the innumerable different states of potentiality to become a cube, a tetrahedron, a dodecahedron, a icosahedron and other regular and irregular forms would have to be both in themselves and in concept [haplos kai kata ton logon] identical, although they are as different as these forms themselves which diverge from each other in a number of directions. Hence, it has been established that the wax ball by being constituted as wax through the actuality of the wax, and as a sphere through the spherical figure, is not constituted through any of its actualities as having a state of potentiality to become a cube. Hence it has a potentiality to be in this state without being constituted in this respect by any of its actualities.57

We come to the third point. Having seen that there are two kinds of states of potentiality, one of which is constituted as such by an actuality while the other is not, the question now is which states of potentiality are constituted by an actuality or, what comes to the same, which actualities constitute potential states as such.

All potential being as such stands in a relation to an active principle; for the subject is potentially something if it can become an actuality through a single act of an active principle. Thus we must also examine those states of potentiality which are constituted as such through an actuality in their relation to an active principle and its operation. Thus a state of potentiality to become something exists in a subject either before the operation, or during the operation, or after the operation of the force through whose activity it is transformed into a state of actuality. But it can obviously not exist after the activity, for if the activity has passed nothing remains that can be realized through this activity; what this activity was capable of actualizing either exists now or has existed in actuality. With respect to this activity at least it does certainly not exist in potentiality, whether or not the latter be constituted through a form. Hence, it remains to consider the states of the subject prior to and during the activity. But the state of potentiality which exists in the subject prior to the activity cannot be constituted through an actuality. For at that point there are only three forms in the subject which must be considered. One is to be envisaged as the terminus a quo for the change, as for example the spherical figure of the wax which is to be transformed into a cube. A second, which is the most deceptive and is therefore the only one considered by Aristotle, is the form which constitutes the subject as that which it actually is. In the case of the wax ball, this is the actuality which constitutes the wax as wax. Finally, there is a third form, in the case of the wax it is softness, which lends a certain disposition to the subject.58 But in considering the second point we have already shown that none of these forms constitutes a potential being as such. Hence the latter, as such, does not possess any actuality. On the other hand, the state of potentiality in which the subject is during the activity of the active principle is indeed a state which is constituted, as such, through an actuality. For the principle acts only to the extent in which the subject receives an influence, i.e., something actual. Now, if the subject is still in a state of potentiality with respect to this force and its activity, then this is due to a further state of potentiality: we have shown this above when we discussed the first point, and everything else said there applies here as well.

The only remaining question is what we should call those states of potentiality which exist during the activity of the acting principle and what to call those actualities which potentialize the subject, as it were. We commonly call them states of becoming or movement,59 and as movement they must be considered actualities which constitute a potential thing as potential. Induction shows this. While the builder builds, that with which he builds is in a state of potentiality which is constituted by actuality, but the building material as such was only a potentiality with respect to house construction and to the edifice. Either the actuality of constructing or the actuality of the edifice must therefore be that which constitutes that higher state of potentiality. But not that of the edifice, for the edifice as such is no longer a potentiality with respect to the builder and this building activity of his; hence, the actuality in question must be the building activity (oikodomesis), and this is indeed a movement (kinesis). One can give a similar demonstration with respect to all other movements.60 If that which is potentially a building is constituted as such through an actuality, then it is presently in the process of being erected, and just this is house construction, hence movement. The same occurs when something heals, when there is a revolution, a jump, etc.61 Hence, movement is the actuality of that which is in a state of potentiality as such, the actuality of the potential as potential. For example, the movement toward a quality (alloiosis) constitutes that which is becoming a quale (poion) in this state of potentiality toward a quality; similarly, the movement toward quantity (auxesis kai phthisis) constitutes that which is about to become a quantum (poson) in this state of potentiality toward a quantity; furthermore, locomotion (phora) constitutes that which moves toward a goal in this state of potentiality for a location. Now, if there is such an intermediate state of potentiality also in the domain of the substantial, then the state of substantial becoming and passing away through generation and corruption (genesis kai phthora) must be formally constituted in the same way, and these, too, will be movements.62

Aristotle, after he has advanced and positively supported his view of movement, seeks to support it further by a polemic against definitions of earlier philosophers, which seems to be aimed especially at Plato;63 he does so in the Physics III.2. and the corresponding part of the eleventh book of the Metaphysics. Here as elsewhere his polemic is never unfruitful, since it always manages to find and isolate what is correct in a mistaken position. He notes that earlier attempts had defined movement as otherness, as inequality, and as non-being. None of these definitions describe the essence of movement, for none of these need to be moved, neither that which is other, nor that which is unequal, nor that which has non-being. It is peculiar to the state of becoming that that which is in the state of becoming has a potentiality to acquire the state of that which has become, while that which has become does not have a state of potentiality to acquire that particular state of becoming from which it arose, as we have seen above,64 while, on the other hand, the equal passes into the unequal, as well as the unequal into the equal, and being into non-being, as well as non-being into being, etc.65 But what occasioned these mistaken definitions? There is indeed something in the nature of movement which could lead one to put it into the order66 of privation. Since becoming does not form a special species of things, but must be reduced to the species of accomplished being,67 as that which is growing large to largeness, and that which is in the process of acquiring a certain characteristic to that characteristic, one is inclined to take it for something indeterminate, something lacking form. What else is one to make of movement? The potentiality (dynamis) by virtue of which something is potentially is not movement, and what is actually [energeia] something is also not in motion; thus the only thing left seems to declare motion to be an unfinished actuality [energeia], an accomplished reality [entelecheia] for which there is no completion, which, unless we envisage it as a privation, seems to be a contradiction. But the puzzle is resolved in this way: as actualization [energeia], movement constitutes something as being in a state of potentiality as such, and the potential is of course incomplete;68 hence, that which completes [vollendet] is indeed a state of incompleteness;69 it actualizes a state which is prior to actuality. "Therefore," says Aristotle, "it is difficult to grasp what movement is, for one either thinks that it either has to be defined as a privation or as a potentiality, or simply as an actuality; yet none of these seem possible. Hence the indicated way is the only one that remains, namely that it is an actuality, but the kind we have described, which is difficult to grasp, but nonetheless possible."70

Thus it becomes clear how, under this interpretation of the definition, everything Aristotle teaches about movement agrees. For what we have just touched upon, viz. that movement does not form a special species of being, but follows the various species as does actuality as such, and potentiality as well, is also fully consonant with this. Movement as actuality constitutes a state of potentiality. Since the states of potentiality belong to the same genus as the corresponding states of actuality, just as the possible body belongs, with the actual body, to the genus of substance, and the potentially white belongs, with the actually white, to the genus of color and of quality, etc., in the same way the thing-in-motion [on kinesei] and motion [kinesis] must be reduced to the particular species of that which comes about through this motion, and must belong to the same genera as the complete being. This is not to say that there is a motion [kinesis] in every species of being, as there is a potentiality [dynamis] and an actuality [energeia]. A state of becoming, i.e., a second state of potentiality which is to be formed by the proper movement, can occur only where there is gradual, continuous becoming, and this can be found only where there are contrary concepts, and hence intermediate states, which are absent where there is an opposition of contradictories. The transformation from non-being to being can only be sudden and momentary. After having declared in Physics III. I and Met. XI. 971 that "there are as many kinds of movement and change as there are kinds of being," Aristotle delineates these matters at some length in the third book of the Physics (and the corresponding part of the eleventh book of the Metaphysics72) and makes the qualification that proper movement is to be restricted to the three categories of quality, quantity and location, where alone the requisite conditions are satisfied, as he shows by a careful investigation.73

Still and all, we do not actually wish to contest the first interpretation; despite the considerable formal difference of the two interpretations they do not, in the end, differ essentially, as we have already pointed out. We note that according to both of them the thing in motion [on kinesei] exemplifies a peculiar mode of union of a potential and an actual state. The second interpretation allows this union to be very clearly indicated in the definition of motion, by saying that motion is an actuality which, by producing its actual state, constitutes a state of potentiality, i.e., constitutes the potential as potential. We see that here, too, the subject which is in the state of becoming occupies an intermediate state between a more distant potentiality and actuality; but by being in this one state, it has simultaneously a state of actuality with respect to becoming, movement; it has potentiality with respect to the form which is approached through movement.

This middle state is also attained by potentialities which have the peculiar characteristic that there cannot be a complete reality corresponding to the potentiality. Just as the concept of movement has something in it which is difficult to grasp, and which at first occasions astonishment and doubts concerning the correctness of the definition (cf. Met. 1. 2; 983al4), many will find it difficult to admit, initially, that there can be a potentiality to which no actuality corresponds, at least not one which exists in rebus though perhaps one which is thought and comprised within its concept since, they will say, something is called potential only in relation to an actuality. Yet such is the case, as the example of any line and of any solid clearly shows. The line, which in actuality is one, can be halved, and thus is potentially two, and since the half is capable of further division, it is potentially four; hence, it is potentially two, four, eight, sixteen, etc. But what is the limit of this potentiality? It does not have a limit; while it is in actuality one, it is potentially infinitely many. But this potentiality is never exhausted by an actuality. The infinitely many lines which are now contained as parts in one line will never actually exist as infinitely many actual lines. Here, and wherever else we are concerned with bodies,74 the infinite exists always only in a state of potentiality, either as a state of potentiality prior to movement (one line has infinitely many parts), or as thing in motion (on kinesei), when a division into infinity is attempted. Similar considerations hold for surfaces, bodies, and other things.75

So much for being insofar as it comprises real potentiality, becoming, and that which is in a state of complete being, being in the sense of potential and actual being [on dynamei kai energeia].


1 Cf. Brandis, op. cit., III, 1, 46, n. 85 and the passage from Prantl quoted there.

2 Books VII and VIII deal with the being [on] of the categories and of substance [ousia] respectively, Book IX of potential and actual being [dynamei kai energeia on].

3 See above p. 1.

4 Cf. Zeller, Philosophie der Griechen, II, 2, p. 238, n. 5. Matter [hyle] must of course be taken in a wider sense in which it includes, in addition to primary matter [prote hyle], also the subjects of the accidents. Then Zeller's remark is correct that "a thing is potentially [dynamei] only insofar as it has matter [hyle] within itself." Met. XIV. 1. 1088bl: "The matter of each thing must be that which is potentially of the nature in question."

5Met. V. 12. 1019b21: "Some things, then, are called adynata [not potent] in virtue of this kind of incapacity, while others are so in another sense; i.e., both dynaton and adynaton are used as follows, etc." As belonging to this merely rational possibility [dynaton] he enumerates: "The possible, then, in one sense, means that which is not of necessity false; in one that which is true; in one, that which may be true." Cf. Met. IX. 1. 1046a8.

6Met. V. 12. 1019b33: "A 'potency' or 'power' in geometry is so-called by a change of meaning." Cf. Met. IX. 1. 1046a7: "Some are called so by analogy." The similarity consists in this: that just as potential being turns into actual being, so from the multiplication of the root with itself is generated the magnitude whose root it is.

7Met. XIV. 2. 1089a28.

8Met. IX. 3. 1047a24: "And a thing is capable of doing something if there will be nothing impossible in its having the actuality of that of which it is said to have the capacity. I mean, for instance, if a thing is capable of sitting and it is open to it to sit, there will be nothing impossible in its actually sitting; and similarly if it is capable of being moved or moving, or of standing or of making to stand, or of being or coming to be, or of not-being or not coming to be."

9Met. IX. 8. 1049blO: "To all such potency, then, actuality is prior both in formula and in substantiality … so that the formula and the knowledge of the one must precede the knowledge of the other."

10Met. IX. 3. 1047a30: "The word 'actuality', which we connect with 'complete reality', has, in the main, been extended from movements to other things; for actuality in the strict sense is thought to be identical with movement."

11Ibid., 6. 1048a25.

12Ibid., a35: "Our meaning can be seen in the particular cases by induction, and we must not seek a definition of everything."

13Ibid., a30: "Actuality, then, is the existence of a thing not in the way which we express by 'potentially'; we say that potentially, for instance, a statue of Hermes is in the block of wood and the half-line is in the whole, because it might be separated out, and we call even the man who is not studying a man of science, if he is capable of studying; the thing that stands in contrast to each of these exists actually."

14Met. IX. 6. 1048a36: "And we must not seek a definition of everything but be content to grasp the analogy, that it is as that which is building is to that which is capable of building, and the waking to the sleeping, and that which is seeing to that which has its eyes shut but has sight, and that which has been shaped out of the matter to the matter, and that which has been wrought up to the unwrought. Let actuality be defined by one member of this antithesis, and the potential by the other." Cf. Schwegler concerning the reading of this passage.

15 Cf. Schwegler, Metaphysik des Aristoteles, 4, 222.

16 Ancient as well as recent commentators are in disagreement concerning the distinction between "energeia" and "entelecheia", but the difference between their opinions is much larger than the difference between the concepts that are designated by these two names. They are indeed applied to different things. It is not so much the case that they differ from one another, but that each differs from itself in different uses [contexts]; for "actual being" [on energeia] is not a univocally, but an analogously used name, as we shall see when the categories are discussed. Thus it could happen that commentators came to opposing views depending on the passage upon which they focussed. Many attribute more consummate reality to entelecheia than to energeia, while Schwegler claims (op. cit.) "energeia is the activity (self-employment) in consummate being, while entelecheia is striving activity connected with dynamis." On energeia as well as on entelecheia mean that which is realized and completed through form. But while the designation "entelecheia" expresses this through the very word, the name "energeia" is taken from movements (as Aristotle teaches, cf. above, n. 10) not because that which is in motion is energeia in the fullest sense, but of all realities movement strikes our eye first. Movement is not asserted of anything that is not real, while other predicates, such as thinkable and desirable, also apply to non-being (Arist., ibid).

17 In connection with Physics 358al9 ff.

18Met. IX. 3. 1046b29: "There are some who say, as the Megaric school does, that a thing 'can' act only when it is acting and when it is not acting it 'cannot' act, e.g., that he who is not building cannot build, but only he who is building, when he is building; and so in all other cases. It is not hard to see the absurdities that attend this view. For it is clear that on this view a man will not be a builder unless he is building (for to be a builder is to be able to build)."

19Met. IX. 3. 1047a4.

20Ibid., a7.

21Ibid., a10.

22Met. IX. 1. 1046a9: "All are originative sources of some kind."

23 See below chap. 5, sect. 3.

24Met. V. 12. 1019al5: "'potency' means a source of movement or change, which is in another thing than the thing moved or in the same thing qua other, etc."

25 Cf. below chap. 5, sect. 13.

26Met. V. 12. 1019a20. "'Potency' then means the source of change or movement by another thing or by itself qua other."

27Ibid., a26: "The states in virtue of which things are absolutely impassive or unchangeable, or not easily changed for the worse, are called potencies; for things are broken and crushed and bent and in general destroyed, not by having a potency but by not having one and by lacking something, and things are impassive with respect to such processes if they are scarcely and slightly affected by them because of a 'potency' and because they 'can' do something and are in some positive state."

28Met. V. 12. 1019a23: "The capacity of performing this well or according to intention … so too, in the case of passivity." This kind of potentiality [dynamis] is here actually mentioned in the third place. According to the order which is used in IX. 1, which we have followed, and which corresponds to the order of things capable [dynata], we have introduced it as the fourth.

29Ibid., a32 ff.

30 See above, n. 5.

31Ibid., b35: "But the senses which involve a reference to potency all refer to the primary kind of potency; and this is a source of change in another thing or in the same thing qua other. For other things are called 'capable', because something else has such a potency over them, some because it has not, some because it has it in a particular way, etc."

32 In order for something to be a potential being [dynamei on] it does not suffice that the principle of an activity should be found in it; doing [poiein] must also belong to it as a proper accident (see below, chap. 5, sect. 13). This is not the case with God.

33Met. IX. 3. 1047a20: "So that it is possible that a thing may be capable of being and not be, and capable of not-being and yet be, and similarly with the other kinds of predicates; it may be capable of walking and yet not walk or capable of not walking and yet walk."

34Met. IX. 10. 1051a34: "The terms 'being' and 'non-being' are employed firstly with reference to the categories, and secondly with reference to the potency or actuality of these or their non-potency or non-actuality." V. 7. 1017a35: "Again, 'being' and 'that which is' mean that some of the things we have mentioned 'are' potentially, others in complete reality." (At this point he has already discussed the categories.) Cf. also De anima II. 1. 412a6.

35 See below chap. 5, sect. 3.

36Met. IX. 6. 1048b6: "But all things are not said in the same sense to exist actually, but only by analogy—as A is in B or to B, C is in D or to D; (for this reading cf. Bonitz, Observationes criticae in Aristotelis libros Metaphysicae [Berlin, 1842]). Some are as movement to potency, and the others as substance to some sort of matter." Cf. below, chap. 5, sect. 13.

37Met. XIV. 2. 1089a34: "Now it is strange to enquire how being in the sense of 'what' is many, and not how either qualities or quantities are many." b15: "What is the reason, then, why there is a plurality of these? It is necessary, then, as we say, to presuppose for each thing that which it is potentially." See Met. X. 3. 1054b28.

38 Cf. the beginning of this chapter.

39Met. IX. 7. 1049a17: "Just as earth is not yet potentially a statue (for it must first change in order to become brass)."

40Met. IX. 7. 1049a3: "Just as not everything can be healed by the medical art or by luck, but there is a certain kind of thing which is capable of it, and only this is potentially healthy. And (1) the delimiting mark of that which as a result of thought comes to exist in complete reality from having existed potentially is that if the agent has willed it it comes to pass if nothing external hinders, while the condition on the other side—viz. in that which is healed—is that nothing in it hinders the result. It is on similar terms that we have what is potentially a house; if nothing in the thing acted on—i.e., in the matter—prevents it from becoming a house, and if there is nothing which must be added or taken away or changed, this is potentially a house; and the same is true of all other things the source of whose becoming is external. And (2) in the cases in which the source of the becoming is in the very thing which comes to be, a thing is potentially all those things which it will be of itself if nothing external hinders it. E.g., the seed is not yet potentially a man; for it must be deposited in something other than itself and undergo a change. But when through its own motive principle it has already got such and such attributes, in this state it is already potentially a man; while in the former state it needs another motive principle, just as earth is not yet potentially a statue (for it must first change in order for it to become brass)."

41 Cf. Physics I. 9. 192b 16.

42 E.g., De anima, II. 1. 412a6: "We are in the habit of recognizing, as one determinate kind of what is, substance, and that in several senses, (a) in the sense of matter or that which in itself is not 'a this', and (b) in the sense of form or essence which is that precisely in virtue of which a thing is called 'a this', and thirdly (c) in the sense of that which is compounded of both (a) and (b). Now matter is potentiality, form, actuality."

43 Cf. Physic

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