The Megarian and the Aristotelian Concept of Possibility: A Contribution to the History of the Ontological Problem of Modality

Abstract

This is a translation of Nicolai Hartmann’s article “Der Megarische und der Aristotelische Möglichkeitsbegriff: ein Beitrag zur Geschichte des ontologischen Modalitätsproblems,” first published in 1937. In this article, Hartmann defends an interpretation of the Megarian conception of possibility, which found its clearest form in Diodorus Cronus’ expression of it and according to which “only what is actual is possible” or “something is possible only if it is actual.” Hartmann defends this interpretation against the then dominant Aristotelian conception of possibility, based on the opposition between dynamis and energeia, and according to which there is always an open multiplicity of simultaneous “possibilities,” the outcome of which remains undetermined. Since, according to Hartmann, reality suffers no indetermination, the Megarian conception of possibility is an account of real possibility, whereas the Aristotelian one is merely an account of epistemic possibility (Frédéric Tremblay).

1 I.

$\left\langle {44} \right\rangle$ The metaphysics of Late Antiquity, and no less that of the Middle Ages, is dominated by the Aristotelian concept of possibility, which is based on the opposition between dynamis and energeia. The internal ambiguity of this concept was soon noticed, being in fact already palpable in Aristotle himself. People clung to it nevertheless, because they could not find any other with which to replace it.

It contains two senses. One is the dual possibility, understood logically, of A and non-A. Its form is that of a disjunction: if A is possible, then non-A is also possible. Since non-A can be decomposed into a series of affirmative cases, the binary contradictory opposition extends into a polyadic contradictory opposition: if A is possible, then B, C, D, etc., are also possible. If one of these cases were actual, then the others would thereby become impossible. However, the dynamis of the case that has become actual would also cease to be. This is because the dynamis and the energeia of one and the same thing never coincide. They are mutually exclusive.

The intuition of an open multiplicity of simultaneous “possibilities,” the outcome of which is not yet determined, is rooted in this concept of dynamis. Dynamis, in this sense, means indetermination (Unbestimmtheit) or irresolution (Unentschiedenheit). It is an incomplete state of being, the determination of whose actuality or inactuality has yet to come from elsewhere.

The second sense is opposed to this indetermination. Dynamis is not a mere being-possible (Seinskönnen), but rather a determinate being-directed-towards actualization (Ausgerichtetsein auf Verwircklichung), the “disposition towards something” (“Anlage zu etwas”), in which this something is itself teleologically anticipated. In this sense, dynamis is not irresolution, but the determinate tendency towards the actualization of something. For example, the seed of a plant is the disposition towards the production of the plant; it contains the formative principle of the plant’s development and determines it through the sequence of its stages.

According to the analogy of this example, all becoming in the world is understood as a teleological impulsion towards the actualization of the eidos. However, this metaphysical sense in the concept of dynamis does not coincide with the logical one at all—as $\left\langle {45} \right\rangle$ little as determination agrees with indetermination. To be sure, according to the Aristotelian conception, the success of the actualization still remains open, both at the stage of disposition and at the intermediary stages of development. This is because there are also external conditions that could hinder the actualization. And, in this respect, the logical indetermination is preserved in the metaphysical context (Verhältnis). However, these kinds of constraints do not rhyme well with the sovereignty of the eidos—and with the corresponding priority of energeia over dynamis—they constitute a kind of foreign body in the Aristotelian worldview, an imperfection, a “contingency,” for the provenance of which no rightful authority (rechte Instanz) is offered.

It is obvious that something is wrong here. The problem does not concern the discrepancy between the logical and the metaphysical senses of the concept. Instead, it is that the dispositional moment (Anlagemoment) in the dynamis cannot be assigned to just any objects in the real world. What applies to the development of organisms—even if, here too, the teleological factor remains questionable—is not valid for just any real process. Just as little can the dynamic character of matter be understood as a tendency-bearing disposition (tendenzhaltige Anlage). Thus, dynamis as neutral indetermination remains alongside dynamis as disposition. From this alone, it becomes clear that we are not dealing with a strictly modal concept.

Nowhere does the inconsistency in the principle of dynamis show itself more clearly than in the problem of κίνησις, i.e., in the central problem of Aristotelian physics. For by κίνησις the ancients understood not only motion, but also occurrence (Vorgang), activity (Ablauf), and process (Prozeß) of all kinds; in short, the dynamic character of actuality (den Werdecharakter des Wirklichen). Now, the essence of this process is exhausted neither by dynamis nor energeia;¹ the one is too little, the other is already too much; one is prior, the other posterior to becoming. It would have to be the transition from one to the other. However, it turns out that, according to Aristotle, there is no third mode that would link them. Thus, it must be an intertwining (Verflechtung) of both modes, which in fact is opposed to their nature—namely, to their separateness (Geschiedenheit)—it must be the energeia of a dynamis insofar as it is nevertheless a mere dynamis.² The contradiction is revealed even more starkly when we introduce pure modal concepts: it is the actuality of a possible insofar as it is precisely a mere possible.

We should surely admit that there is a certain greatness in Aristotle’s way of dealing with the problem; that he breaks away from his own system of original concepts without giving it too much thought when the specificity of an unavoidable problem demands it. He is not dogmatically attached to previously attained results; he preserves what is acquired, flexibly and adaptively. Nevertheless, he does not go so far as to revise the modal concepts that he himself introduced; he $\left\langle {46} \right\rangle$ rather leaves the contradiction in the definition of κίνησις out in the open. That this was possible at all is the best proof that dynamis and energeia are not, at bottom, modal concepts. In any case, the ancients were not able to conceptually master the problem of kinesis. They understood becoming as the opposite of being, not as a specific kind of being, let alone as the fundamental form of real being (Realseins). For this reason, the mode of being (Seinsweise) of what is moved as such had to remain incomprehensible to them.

The reason why the Aristotelian concept of possibility has persisted after all, the reason why it could dominate the metaphysics of the Middle Ages and even that of Modernity, is completely different. In those centuries, metaphysical thinking consisted of almost nothing other than teleological systems. Back then, people did not dispute the validity of [the theory of] immanent purposes, but only their specific kind, their origin, and their relation to reality. Moreover, the place that was conceded to logic compelled them again and again to hang on to the disjunctive [concept of] possibility. For logical possibility is, in fact, the simultaneous possibility of A and non-A. The mistake did not lie in recognizing it, but in implicitly identifying it with real possibility (Realmöglichkeit).

It is only with the dissolution of the Aristotelian concept of form that a completely different kind of being-possible (Möglichseins) and of being-actual (Wirklichseins) could appear on the horizon. This turn began in the fourteenth century, and came to fruition in the seventeenth.

2 II.

In light of this state of affairs, it is historically significant that the Aristotelian concept of possibility was neither the first nor the last in ancient philosophy. There was another one before it, which Aristotle knew very well, against which he ardently fought, and which was eventually almost eliminated. It is the concept of possibility of the Megarian School, founded by Socrates’ student, Euclid. This concept is in many respects much closer to the real context (Realverhältnis) of possible being (Möglichseins) than is the Aristotelian dynamis, and, in contrast to the latter, is a genuine ontological concept of possibility. It has, however, received almost no consideration from later [philosophers]—except in the polemic of the Stoa—presumably for no other reason than that it seemed absurd from the ever increasingly dominant Aristotelian viewpoint.

The Megarian concept of possibility asserts that “only what is actual is possible,” or “something is possible only if it is actual.” At any rate, the concept was passed down to us by Aristotle in this presumably reliable form.³ The question arises, naturally, as to what this strange sentence actually means. For, at first glance, it seems today as $\left\langle {47} \right\rangle$ paradoxical as it seemed in Aristotle’s time. We should not be surprised that it was passionately fought. But we need to make a detour to answer the question of its meaning.

Today, we can only imperfectly reconstruct the doctrine of the Megarians. Among the Socratic schools, this one gives an impression of archaism due to its strong Eleatic character. Its fundamental conviction was the unity and immobility of being. Combined with it was the theory of forms taken from Socrates, which opposed a certain multiplicity to this unity. It is no longer possible to understand how the latter was consistent with rigid [Eleatic] unity; it seems that this internal contradiction could never be resolved, because the immediate successors of Euclid had already abandoned [the thesis of] the plurality of the forms of being and saw only a plurality of names for the one identical being behind them. They clung tightly to the suppression of becoming and of motion once carried out by Parmenides. There is no doubt that the old Zenonian paradoxes of motion played a leading role here. They did not limit themselves to these, however, but added new arguments.

Now, among the latter, there is a modal argument that strikes us as very peculiar: nothing can become which does not already exist, because becoming presupposes the being-possible of what is still inactual (Unwirklichen). The inactual is not possible, however, for only that which is actual is possible. This idea is still very close to Parmenides’ claim that becoming contains being and nonbeing at the same time, which is contradictory. Likewise, in the mere possibility of one and the same thing seem to be opposed being and nonbeing; if it is not actual, it must be nonexistent, but if it is not impossible, it must exist. As a result, this argument led to the same suppression of becoming.

The conception of the opposition between possible and actual that is implied here did not attract much attention in this simple form, but attracted greater attention in a more complex one. The new form was given by Diodorus Cronus, a late disciple of the School and contemporary of Aristotle. It was known under the pretentious title κυριεύων λόγος [i.e., master argument], and seems to have been held in high esteem for a certain time. And since the Megarian doctrine of possibility—as long as it was not forgotten—was known in this variation by the later [philosophers], we must first say something about it here.

We also only know the κυριεύων through a later tradition (from Arrian), and we need this interpretation to be able to reconstruct its meaning. Diodorus started from three propositions that he took to be commonly accepted, but between which he saw a contradiction. These propositions are: (1) “Everything that has passed (Alles Vergangene) is necessarily actual”; (2) “The impossible does not follow from the possible”; and (3) “What is possible is neither actual nor will be.” Now, Diodorus thought that the third of these propositions—obviously a proposition that expressed a received conviction of his time—contradicted the first two. He thus decided in favor of the first two propositions and $\left\langle {48} \right\rangle$ concluded that “Nothing is possible that is neither actual nor will be actual.”⁴

The concluding proposition corresponds nearly, if not exactly, to the fundamental principle of the School according to Aristotle’s testimony, namely, that only what is actual is possible. However, the precise form of the argument cannot be immediately inferred from the above-stated propositions. Only one thing is clear: there must have been an apagogical proof, in which the third proposition, which was in fact the negation of the concluding proposition, constituted the point of departure; if we consider this proposition as valid, we contradict the first two, and since the latter are considered proven, it has to fail, thus its opposite has to be accepted.

Reconstructions of the argument are not lacking. They differ very little from each other, varying mostly in their usage of the first proposition; indeed, some make it look almost superfluous. The simplest option would nevertheless be to give it first place in the argumentation, corresponding to the order of enumeration that has been transmitted to us. We would then arrive roughly at the following version.

Once something has occured, it cannot be made not to occur; it is necessarily actual. For the merely possible, only the present or future remains, i.e., it could at most be something that either is or will be (if, that is, a merely possible “is” something at all). Now, however, the mere being-possible of something means precisely that it can also remain inactual (nonexistent), thus it does not even need to exist either now or later. Let us assume that something were possible which neither is nor will be, then from a possible an impossible would have to follow; for, if time passes and the possible does not become actual, then it is afterwards, as something past, necessarily nonexistent, i.e., an impossible. Since, according to the hypothesis, it was possible beforehand, then from a possible came an impossible. But from a possible an impossible cannot arise; for an impossible consequent cancels the very possibility of that of which it is the consequent. Therefore, there can be no possible that would become actual either now or later. Or, positively formulated: what is possible is only that which is either already actual or will at some point become actual.

This argument, so famous in its time, no doubt had something convoluted and sophistical about it. Even so, it is meaningful and not without acuteness, if the second of the supposed propositions is correct. For in this proposition—δυνατῷ ἀδύνατον μὴ ἀκολουθεῖν—the thesis adopted by the demonstratio apagogica (apagogischen Beweises) fails. However, it is precisely in this proposition $\left\langle {49} \right\rangle$ that the sophistry is rooted. For it is ambiguous in the way that it is used. The ἀκολουθεῖν means at once the logical sequence and the chronological sequence. But these are far from being one and the same.

In his time, Eduard Zeller—in a lecture given in 1882 at the Academy—thoroughly clarified this state of affairs.⁵ If the proposition were supposed to be self-evident, then it could only mean: the possible is that whose actualization results in nothing impossible (contradictory). It is in this sense that we find the proposition in Aristotle, who sees in it the essential determination of the possible (ἐνδεχόμενον, δυνατόν) and repeatedly formulates it accordingly.⁶ What this proposition asserts is quite simple: that out of which the impossible comes is itself impossible; thus, possible is only that which, even if it were to become actual, entails nothing impossible. However, this “entailing” is here to be understood in the logical sense. Zeller is of the opinion that Diodorus took the proposition from Aristotle, but that he misunderstood it completely. Because evidently for Diodorus ἀκολουθεῖν means a chronological sequence, and a highly determinate one at that. For in the context of the κυριεύων, the proposition means that something that was previously possible could not be impossible at a later time. If indeed the possibility is disjunctive, and if A was previously possible, then non-A was also possible; if, however, A meanwhile became actual, then non-A must at the same time have become impossible; the being-impossible (Unmöglichsein) of non-A would thus have to be “entailed” by its being-possible (Möglichsein). And it is precisely this that Diodorus deemed impossible.

Zeller’s explanation may be unsurpassable, insofar as it concerns the obvious confusion, proper to eristic thought, of logical and chronological “entailment.” And since it concerns the true core of the κυριεύων, the latter is revealed as a quaternio:⁷ that whose actualization entails nothing impossible can, just for this reason, itself become impossible if its opposite has become actual, even if it was completely possible before its actualization. We can only wonder why critics as sagacious as Chrysippus and other Stoics, who went through lots of trouble to refute the κυριεύων, did not pay attention to this central misunderstanding.

We may leave open the question whether Diodorus adopted the proposition regarding the δυνατόν from Aristotle. Although it is probable, we can of course not prove it. Whether the two contemporaries drew from a common source, or simply appropriated a viable ownerless idea of their time, it was still no doubt Aristotle’s interpretation that correctly rendered the original sense of the proposition. $\left\langle {50} \right\rangle$

3 III.

Is this the whole meaning of the Megarian concept of possibility? And is it thus exhausted along with the κυριεύων?

The previous presentations, as far as they engage with this obscure subject, show no sign of taking us any further. It seems clear that the argument is fallacious. Furthermore, it attempts at demonstrating a dubious thesis—because it appears that, according to this thesis, possibility and actuality coincide, such that their difference would disappear (the modal concepts themselves would thus be abandoned)—and the whole thing proves to be an eristic artifice, aimed at demonstrating the impossibility of becoming, after the Zenonian arguments seemed to have lost their persuasive power.

This is not at all the case. It seems that we can in fact better account for the Megarian theory of possibility on historical as well as systematic grounds. An opportunity presents itself for this purpose as soon as one understands how one-sided and ontologically inadequate the Aristotelian concept of possibility is, and how close these thinkers had come, in an era open to fundamental metaphysical questions, to understanding real possibility (Realmöglichkeit) in a completely different way. Before proceeding, we offer three interpretive considerations that conflict with this now conventional interpretation.

Firstly, the fallaciousness of an argument does not entail the falsity of the proposition that it aims at establishing. With his κυριεύων, Diodorus wanted to prove a thesis that already stood independently of such argumentation and did not require it. He was wrong to do so, for he thereby made his thesis ambiguous and provoked a storm of attacks that was in truth not aimed at the thesis, but rather at its sophistical demonstration. For those who followed, however, the ontological seriousness of the problem of possibility was buried under the amusing pro and con of the hairsplitting conceptual game.

Secondly, concerning the thesis itself: it does not mean that possibility and actuality coincide, and even less that they are identical. It only means that neither occurs without the other, i.e., that what is possible in the real world must also be actual—in precisely the same way that what is actual must also at least be possible. This evidently does not mean that its being-possible (Möglichsein) is one and the same as its being-actual (Wirklichsein). The association of the modes in real contexts (Realverhaltnis) manifestly has an entirely different meaning than that of identity. And what exactly could “mere possible” (bloß Mögliches) even mean? Certainly, it presents no difficulty in thought or in theory. But what role could it play in reality? Are there two kinds of beings in the real? Is there a spooky multiplicity of possibles in the midst of the actuals? Dispositions and capacities, in the Aristotelian sense, certainly exist in the real world; but they are far from being something merely possible, for they are thoroughly actual dispositions and capacities. In contrast, that which is realized by means of them—in other words, that end toward which they are oriented—is in no way really possible through them alone. $\left\langle {51} \right\rangle$ In fact, ever more conditions are required for them. The disposition does not determine whether the latter are there or not.

Thirdly, the enormous absurdity of the metaphysical conclusion that was drawn from this thesis in the Megarian School has in fact nothing to do with the thesis. When the Megarians denied movement and becoming, they did so on the ground of their worldview and not on the ground of the modal argument. This argument was rather used after the fact, and it was used wrongly. This is because movement—spatial as much as qualitative—is not at all a passage from being-possible to being-actual, but a passage from one state to another state, where the states are themselves all equally possible and equally actual. This conception of becoming had already been prevalent for a long time in this era; Empedocles, the Atomists, and Anaxagoras had taught it. However, Aristotle’s teleologism would not allow it, and obviously would admit even less the rigid Eleatism of the Megarians.

Concerning the first two points, it is important to distinguish the original theory of possibility of the ancient Megarians from that of Diodorus. This, too, has been done in an exemplary manner by Zeller in his Academy essay, in contrast to later accounts.⁸ When Aristotle says “εἰσὶ δέ τινες οἳ φασὶν οἷον οἱ Μεγαρικοί…”, this can admittedly apply also to Diodorus; but it more likely literally refers to the whole School, and even perhaps to the founder Euclid, who first renewed the Eleatic way of thinking.

As a matter of fact, the theory to which Aristotle referred appears to have been a theory other than that of Diodorus. What is most striking here is the fact that Aristotle does not seem to know the κυριεύων; in any case, we do not find it in his work, not even in the chapter of Metaphysics (θ, 3), which is essentially a dispute with the Megarian theory of possibility.⁹ In addition to this, there is a difference of content. What Diodorus wants to demonstrate is only this: “nothing is possible that neither is actual nor will be actual.” Accordingly, something can very well be possible that is currently not actual, if only it later becomes actual. Aristotle’s “Megarians,” to the contrary, claim much more crudely, affirmatively, and without recourse to the future becoming-actual: ὅταν ἐνεργῇ μόνον δύνασθαι, ὅταν δὲ μὴ ἐνεργῇ οὐ δύνασθαι… This proposition asserts more: something is only possible as long as it is actual; i.e., it is possible neither before it is actual nor after. The example that immediately follows in Aristotle’s text emphasizes precisely this unambiguous temporal meaning: “the builder, for instance, when he $\left\langle {52} \right\rangle$ is not performing the act of building, cannot build either; he can only do so as he builds and as long as he builds.”

Whatever historical distinctions may be drawn here, what matters for the philosophical evaluation of the Megarian concept of possibility is not so much the convoluted κυριεύων, but the simple and clear thesis that Aristotle has preserved for us, and whose detailed critique has honored. The question of the proper meaning of this thesis now arises, however. For in Aristotle’s presentation—and we do not have a better one—it does indeed look absurd.

He presents it as a nonsensical thesis and thinks he can get rid of it easily: οἷς τὰ συμβαίνοντα ἄτοπα οὐ χαλεπὸν ἰδεῖν. If powers, dispositions, and capacities exist only as long as they exercise their function (ὅταν ἐνεργῇ), then it must follow that the builder is no longer a builder when he is not building; for to be a builder means nothing else than being able to build. Likewise, those who see would have to be blind many times a day, namely, as soon as they close their eyes; the objects of perception would no longer be perceptible if they were not being perceived by someone. We would also not be able to say that someone who is sitting can get up, because as long as he is sitting, he is not getting up, but if he actually gets up, then he is no longer sitting.¹⁰

Such inconsistencies must naturally result, because Aristotle surreptitiously substitutes his own concept of dynamis. The latter is not a pure modal concept of possibility at all, but rather signifies a power (Vermögen), disposition (Anlage), capacity (Fähigkeit)—as the examples clearly show—and not a real possibility (Realmöglichkeit). Underlying all of this is the idea of a disjunctive double possibility (Doppelmöglichkeit), whose form of being signifies indetermination or irresolution. We spoke of the internal difficulties of this idea in the first section. It leads to a picture of the real world in which there is an overabundance of the “merely possible” (bloß Möglichen) crammed everywhere in the midst of the actual (des Wirklichen), as if it were a secondary kind of being, as the prior state (Vorzustand) of the not-yet-existing (Nochnichtseienden) with an impulse towards being—although many of them never reach [the state of] being.

But is there actually such a thing in the real world? Does not this multiplicity of possibilities on the loose, as it were, exist only in thought, i.e., in those of our reflections which take into account a plurality of eventualities, because they cannot embrace the totality of real situations? What principle (Instanz) should afterward determine that the merely possible become actual? What is the principle of selection that intervenes in this multiplicity and that decides between being and nonbeing—or, should we say, between becoming (Werden) and non-becoming (Nichtwerden)?

$\left\langle {53} \right\rangle$ Following the Aristotelian way of thinking, this principle can only be the εἶδος. This is because there is no other determining (motive) power. Now, it just so happens that the dynamis already contains the εἶδος in itself, only not as actualized. What is added in the passage to energeia is not the formal determination (Formbestimmtheit), but rather the mode of being (Seinsmodus). Thus, only contingency (Zufall) would remain. However, actualization—for instance, of the form of the species in the growth of a plant—should not be contingent.

4 IV.

One must have a clear vision of the difficulties inherent in the Aristotelian concept of possibility in order to correctly understand the sense of the Megarian concept, so passionately opposed. The latter contains everything that the former lacks: full determination, univocity, and decisiveness of being-possible (Möglichseins). This is precisely what the proposition “only that which is actual is possible” means. According to this conception, there is no “mere possible” in the real world. There is room for it in abstraction, in concepts, in logical relations—and if among “what is” at all, then at most in an ideal realm of timeless intelligible forms of the Platonic kind—but not in the world in which we live.

We have to ask, however, how we know that this is the meaning of the Megarian concept of possibility. To this question, we would answer that this meaning can be found in the examples provided by Aristotle, examples by means of which he intends to carry his refutation. This is because, upon closer analysis, they all speak against a teleological and ontically undetermined concept of dynamis, and indirectly provide justification for the Megarian position.

One might reason as follows: is it true that the builder “can build” when he has nothing but his τέχνη (the dynamis in the sense of capacity)? Apparently not. Without his own capital or building contract, a piece of land, material, and a labor force, he “can” in fact build nothing. We may call these external conditions in comparison to the τέχνη, which is an internal condition; but who would argue that they are not as essential as the others, and that building is simply impossible without even one of these conditions? From the ontological point of view, the possibility of building consists precisely in a reciprocal interaction between external and internal conditions, and indeed, such that it first arises when the two kinds of conditions are satisfied at the same time. Genuine real possibility (Realmöglichkeit) does not reside in the τέχνη as a person’s acquired and inalienable skill. The concept of δύνασθαι, which is limited to powers and faculties of this kind, is superficial and ontologically insufficient. Naturally, the builder does not cease to be a builder when he is not performing the act of building, and he does not lose his τέχνη either; but being able to build is not reducible to the mere fact of being a builder.

The situation is similar with the other examples. What about the perceptibility of the αἰσθητά (sensible objects)? Is it true that they “can” be percieved when no perceptual organ is directed towards them? Evidently, it is not sufficient $\left\langle {54} \right\rangle$ for this effect that they simply be what they are, namely, apt to affect an organ; the organ must also be there, opened and turned towards them. The issue is veiled here by the ambiguity in the concept of “being perceptible” (Wahrnehmbarseins), insofar as the latter appears, on the one hand, as a merely partial condition, and, on the other hand, as a fully real possibility. The former subsists continuously in the things, whereas the latter depends on the existence of the subject and its stance towards the thing.

Conversely, what is the situation with the one who sees and hears? Is it true that he “can” always see and hear everything that is visible and audible? What is too far away does not reach him; he cannot see in the dark, and he cannot understand a word in the midst of a great racket. Evidently, on this account, he does not need to be blind and deaf “many times a day.” The sensory faculty remains, but it is insufficient for “being able to” see and hear. Only the addition of external conditions completes the real possibility.

The paradox of the “sitter” is a merely apparent one, of course. Or should the fact of sitting be sufficient on its own for being able to get up? Certainly not. The sitter “can” not get up before making the appropriate effort. This effort can be so minimal that we overlook it, but who would argue that without it getting up is effectively impossible? One could perhaps object to this that when he initiates the necessary effort, he is at the same time actually in the act of getting up, and is no longer sitting. To this we may reply: the sitter, so long as he sits, is in fact not up, and indeed for no other reason than that he “can” get up as long as he remains in the sitting position. This conflicts with the Aristotelian concept of possibility, but it is in accordance with the Megarian one. For the latter does not say anything else than that someone “can” get up when he is actually getting up.

Accordingly, we may ask in a general manner: is what Aristotle is teaching true, that something could be possible without being?¹¹ If one understands the δυνατόν merely as capacity, disposition, power, or otherwise as mere partial possibility (Teilmöglichkeit), then it is certainly true; but then it does not mean that the thing is also already really possible. But, understood in the sense of complete real possibility, the proposition is not true. Thus, from the ontological point of view, the Megarian thesis is right against Aristotle: what is really possible is only that which is actual (or, for a more complete formula: what either is, or is in the process of becoming).

The Megarians were the first to have a strictly ontological concept of possibility—in contrast to that vague popular concept of merely partial possibility that already speaks of being possible (Seinkönnen) when a single isolated condition is present, without paying attention to the remaining conditions of real possibility. They were the first on whom it dawned, perhaps without $\left\langle {55} \right\rangle$ being clearly aware of it, that the being possible of a thing belongs to a long chain of conditions—and in fact real conditions—which must all actually exist in order to make a thing possible.¹² It is a concept of possibility that neither has to do with logical non-contradiction nor with teleological “potency” (Potenz), but in fact displays an entirely peculiar nature, comparable to no other relation—namely, a purely modal nature.

In this way, the Megarians were also the first to grasp that the really possible (real möglich) does not mean “able to be” (sein können) this way or that way, but in fact “able to be” this way and not otherwise. In accord with the core issue, they tied being-possible firmly together with being-necessary; for “to not be able to be otherwise” means “to have to be.” Thus, the tendency towards the development of a viable concept of necessity, as well as an even more significant, purely ontological concept of actuality, would be consistent with their thought (in contrast to the Aristotelian concept of energeia, which denotes only the actualization of the eidos).

Whether one of these consequences was actually drawn, we have no evidence. The Megarians were restrained from going in this direction through their distinctly Eleatic mode of thinking: they were not able to transfer what they saw so clearly onto the process of becoming (κίνησις)—the only place where it first might have become fruitful—for they had even excluded becoming from being.

If we set aside these internal and self-imposed limits of the School, it is not anachronistic to credit the Megarian thinkers with a keen reflection on the interdependence of conditions. This is because the quest for the αἰτιολογία of phenomena had been taken up since the beginnings of atomism, and it is not likely that it was unknown to a man such as Euclid.¹³ $\left\langle {56} \right\rangle$

5 V.

The historical considerations brought to bear here, insofar as they contain a very specific interpretation and evaluation of an ancient way of thinking, urge on us a systematic clarification of the ontological principle of possibility. This account is grounded on a novel interpretation of the nature of real possibility; and there is an internal connection, which, by virtue of this interpretation, allows the Megarian concept of possibility to appear in a very different light when compared to the conventional concept, which is still strongly influenced by the Aristotelian modal concept. No one can see more in historical sources than one can conceive systematically; one can only ever recognize, in the historical distance and through the foreignness of the concepts and turns of phrase handed-down, that to which one brings the epistemic foundations of his own current thinking. Only on the basis of a change in contemporary ontological thinking can new ways of understanding the insights of remote predecessors also be engendered, to the extent that the latter evolved along a kindred line of thought.¹⁴

In order to justify what was just said, we must provide a systematic consideration of the ontological concept of real possibility, of how it stands in opposition to mere essential possibility (Wesensmöglichkeit), as well as in opposition to logical possibility and epistemic possibility (Erkenntnismöglichkeit). If taken seriously, that would be a difficult and lengthy piece of work.¹⁵ We can obviously only deal with a few indications here. Since we have done preliminary work towards understanding the issue in the discussion of Aristotle’s examples above (in the preceding section), it does not seem futile to summarize briefly the decisive points in favor of a concept of possibility closely related to that of the Megarians.

There are two such points. The first consists in the formal relation of the modes of reality (Realmodi). What is really actual (realwirklich) must at least also be really possible (realmöglich); an impossible cannot be actual. This entails that real actuality (Realwirklichkeit) already implies real possibility (Realmöglichkeit), and must in fact contain it.

Now, what is contained in real actuality (Realwirklichkeit) cannot be the disjunctive double possibility, for the possibility of non-A can evidently not be preserved in the actuality of A; it is in fact excluded from it. Thus, the relation of the modes of reality (Realmodi) requires the separation of the double possibility into a distinctly $\left\langle {57} \right\rangle$ positive one and a distinctly negative one. This state of affairs may be referred to as the “law of the separation of real possibility”: in real relations (Realverhältnis) the possibility of A never combines with the possibility of non-A (as, for instance, in the logical relation of judgment), but they mutually exclude each other.

Moreover, it follows from this that if the real possibility of A excludes the real possibility of non-A, then A, in virtue of this possibility, is already necessarily real. This is because that whose contradictory opposite is impossible must, for its part, be actual. This conclusion leads us directly to the Megarian proposition: that which is possible in the real context is only that which is actual in it.

This does not at all mean, as we can clearly see from this train of thought, that possibility would already itself be actuality. The possible is not possibility, and the actual is not actuality. The mode (Modus) is in the thing (Sache); not the thing itself, but “its” mode of being (Seinsmodus). The possible is at the same time actual, but its being-possible is not the same as its being-actual. Its possibility lies in its being supported by the conditions on which it depends in the real context (Realzusammenhang); its actuality, in contrast, is its real existence itself. We see clearly how much these two differ by the fact that often in life we have certain knowledge of a thing’s being-actual, but we in no way grasp its possibility.

The second point, however, is completely different and independent of the first. It is not rooted in the relation of the modes, but in the structure of the real context (Realzusammenhang). The being-possible of something in the course of events always depends on a whole chain of conditions. A determinate real process (Realvorgang) “can” only unfold when all the conditions of its possibility—up to the last—are assembled. As soon as they are all assembled, and if nothing more is lacking in their completeness, then the process can no longer hold back, i.e., it already actually unfolds. This is because “not-being-able-to-hold-back” (Nichtausbleibenkönnen) means precisely the necessity of becoming actual (Wirklichwerdens). The process becomes actual at the instant when its real possibility is completed (perfekt wird).

We thus arrive in this way too at the proposition of the Megarians. Something may very well be mentally possible (denkmöglich) or logically possible (logisch möglich), while being thoroughly inactual. It is really possible only when it is actual, or when it is about to become actual. A “mere possible” does not exist in the real world.

This fact is obscured by our imprecise everyday way of speaking, although at bottom we know it very well. We say of a stone that is lying close to a hillslope that it “could” roll down and thus cause this or that damage. However, we know that in truth it “can” not roll down at all unless some trigger makes it lose its stability. A last link in the chain of conditions is still lacking; if the latter is supplied and the chain is completed, then the stone “must” roll down. It thus “actually” rolls as soon as its rolling becomes really possible.

And is it any different with Aristotle’s builder? We certainly say that he “could” build if only he had the knowledge and competence. But we do not at all mean $\left\langle {58} \right\rangle$ by this real possibility, only the τέχνη; we know only too well the helplessness of his “not-being-able-to” when he is standing there unemployed, due to the unfavorable circumstances of the construction industry. It is absurd to deceive oneself about the fact that it is an entirely trivial equivocation that makes one sense of “could” sophistically play against another. The one is and remains mere capacity, which must first wait for its chance in life, whereas the other is the full real possibility, which depends on a thousand unpredictable real conditions. Who would doubt that the one who waits for the chance, as soon as he finds these conditions assembled somewhere, actually begins building? What Aristotle denied is thus true: when he is not actually building, the builder “can” in reality not build. And so, the mocked Megarian proposition maintains its rights.

We stand today on the threshold of a new ontology—a categorial analysis of “being qua being,” which promises to be fundamentally different from the ancient doctrine of ens and essentia, form and matter, potency and act. It has already attracted lots of attention, more perhaps than its still very awkward and one-sided beginnings deserved. These beginnings are still too attached to the tradition, too prejudiced by the ancient concept of possibility.¹⁶ We must first gain this new orientation in order to be able to deal with the problems of contemporary metaphysics; and when we have won it, we must then learn to work with the newly developed fundamental concepts. From the earliest times, it was the conversation on possibili et impossibili that contained the most important information about the problem of being. Everything depends on the version of the concept of possibility that one adopts.

This has not changed. What has changed is the way in which we have to tackle the problem of possibility as one of real interconnections (Realzusammenhänge). Contemporary man has learned to think historically. Standing at such a crossroads, he understandably looks for help in the forgotten ideas of history. And since the Aristotelian concept of possibility has now played itself out and must be replaced by another one, it is quite natural that the inquiring gaze falls upon this other, earlier concept of possibility that was, back then, dismissed and historically almost annihilated. But the most astounding thing is that, despite all paradox and all historical distortion, it proves to be systematically sound.