diogenes of babylon

Koninklijke Brill NV, Leiden, 2007 DOI: 10.1163/156852807X180072

Phronesis 52 (2007) 188-209 www.brill.nl/phro

Th e Ontological Argument of Diogenes of Babylon

Michael PapazianDepartment of Religion and Philosophy, Berry College,

Mount Berry, GA 30149-0550, [email protected]

Abstract An argument for the existence of gods given by the Stoic Diogenes of Babylon and reported by Sextus Empiricus appears to be an ancient version of the ontological argu-ment. In this paper I present a new reconstruction of Diogenes argument that diers in certain important respects from the reconstruction presented by Jacques Brunschwig. I argue that my reconstruction makes better sense of how Diogenes argument emerged as a response to an attack on an earlier Stoic argument presented by Zeno of Citium. Diogenes argument as reconstructed here is an example of a modal ontological argu-ment that makes use of the concept of being of such a nature as to exist. I argue that this concept is a modal concept that is based on the Philonian denition of possibility, and thus that Diogenes argument is a source of important evidence about the use of non-Stoic modalities in the post-Chrysippean Stoa. I conclude by arguing that the objections made against considering Diogenes argument as ontological are unfounded and that Diogenes argument clearly resembles modern versions of modal ontological arguments.

Keywords Stoics, ontological argument, ancient logic

Even the most casual student of philosophy will associate the ontologi-cal argument for the existence of God with St. Anselm. Anselm is widely celebrated as the inventor of this argument and, accordingly, a philoso-pher who has made an original contribution that has no Greek prece-dents. tienne Gilson has made the even stronger claim that no ancient Greek philosopher could have invented the argument: Th inkers like Plato and Aristotle, who do not identify God and being, could never dream of deducing Gods existence from His idea.1 For Gilson, it is an

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undisputed fact that no trace of [the ontological argument] exists in Greek thought.

Several historians of philosophy have called Gilsons claim into ques-tion. Some have found adumbrations of Anselms argument in Plato and Aristotle.2 Perhaps the most promising candidate for an ancient ontological argument is the argument for the existence of gods attrib-uted by Sextus Empiricus to the Stoic Diogenes of Babylon. In this paper I focus on three distinct but related matters concerning Dio-genes argument. First, I present a reconstruction of Diogenes argu-ment, a reconstruction that I argue is preferable to an alternative reconstruction presented by Brunschwig (Part I). I then discuss the conception of possibility that plays a central role in Diogenes argu-ment and examine its relation to the other modal denitions current in Hellenistic logic (Part II). Finally, I consider Brunschwigs claim that Diogenes argument is not ontological. I argue that Brunschwigs con-clusion that Diogenes saw the possibility of reasoning along the lines of the ontological argument but deliberately refrained from using it3 is unwarranted. Instead I hold that Diogenes argument is indeed an onto-logical argument, specically a modal ontological argument (Part III).

I. Diogenes Argument

Th e argument in question is a reformulation by Diogenes of Babylon of an argument given by Zeno of Citium. Th e arguments of Zeno and Diogenes are reported by Sextus Empiricus (M. 9.133-6). Sextus claims that Zeno presented the following syllogism:

A1) One may reasonably honour the gods. [ ]

A2) One may not reasonably honour those who do not exist. [ ]

A3) Th erefore, the gods exist. [ ]

1) Gilson (1936), 59. 2) See Brunschwig (1994), 170 for references. 3) Brunschwig (1994), 172.

M. Papazian / Phronesis 52 (2007) 188-209 189


190 M. Papazian / Phronesis 52 (2007) 188-209

In response, certain philosophers constructed a parallel or parody argu-ment ():

B1) One may reasonably honour the wise. [ ]

A2) One may not reasonably honour those who do not exist. B3) Th erefore, wise men exist. [ ]

Th e parallel argument cannot be accepted by the Stoics, since according to Stoic doctrine the wise man has remained undiscoverable up to now (M. 9.133-4).

Zenos syllogism is one of a series of arguments he presented in shorter and more compressed (brevius angustiusque) form.4 Schoeld has convincingly argued that the parodies or parallel arguments were all the work of Alexinus, a Dialectician and contemporary of Zenos.5 Alexinus standard method against the Zenonian syllogisms was to keep one premise and to substitute the other premise with one of identical form. Th e conclusion of the parody would always be repugnant to the Stoics. For example, Philo of Alexandria reports one of Zenos syllo-gisms concerning whether the wise get drunk:6

If one would not act reasonably in entrusting a secret to a drunk, but if one would act reasonably in entrusting a secret to a good man, it follows that the good man does not get drunk.

In this case, the parallel argument alters the major premise to read, One would act unreasonably in entrusting a secret to someone who is melancholy, asleep, or dying (Philo 177). It follows that the good man is not melancholy but also that he needs no sleep and is immortal.

Diogenes attempted to save Zenos syllogism for the existence of god from the parody by claiming that what Zeno really meant to say (or should have said) in A2 was:

4) See Cicero, De natura deorum, 2.20. 5) Schoeld (1983), 36. DL 2.109 states that Alexinus was one of the successors of Eubulides. 6) Philo, De plantatione, 176 (Colson and Whitaker).



C2) One may not reasonably honour those who are not of such a nature as to exist [ ].

From C2 and A1, it may be concluded that

C3) Th e gods are of such a nature as to exist. [ ] (M 134-5)

Now, however, there is the problem of getting from C3 to the origi-nal conclusion of Zenos argument. Diogenes tries to show that if the gods are of such a nature as to exist, then the gods do exist. Th e reason-ing is as follows:

D1) If the gods did exist at one time, then they also exist now. [ , ]

Th e support for D1 is that the gods are indestructible and ungenerated according to their conception ( ) just as atoms are indestructible and ungenerated according to their conception (M 9.135). Th us, not being liable to destruc tion, the gods of the past must exist even today.

Diogenes must assume that

D2) If the gods are of such a nature as to exist, then they must have existed some time in the past.

From C3, D1, and D2, the desired conclusion A3 can be derived.

Diogenes then shows that a parallel argument leading to the conclu-sion that the wise exist is not sound because it is not the case that

E1) Since () the wise are of such a nature as to exist, then they must also exist now. (M 9.135-6)

Diogenes argument raises a number of questions. First, what does it mean to say that something is of such a nature as to exist? Second, why must it follow from the proposition that the gods are of such a nature



as to exist that they must have existed in the past? And third, why does the past existence of the wise men not follow from their being of such a nature as to exist? Sextus leaves us in the dark about these questions.

Any attempt at reconstructing Diogenes argument will require an interpretation of existing by nature or natural existence. Brunschwig presents three possible interpretations:7

1. Necessarily existing 2. Possibly existing 3. Normally existing

1 can be excluded because it would make Diogeness attempt to argue from the gods existence by nature to their actual existence superuous. If Diogenes understood natural existence to mean necessary existence, he would not have bothered to devise the supplementary argument that attempts to show that existence by nature entails actual existence. 2 is too weak according to Brunschwig because merely possible existence does not ensure existence at some time in the past, thus making D2 a false conditional. Instead, Brunschwig proposes that existence by nature must be some third mode of existence weaker than 1 but stronger than 2. He calls this mode of existence normally existing. For Brunschwig, the properties which a given type of being possesses by nature are nor-mally possessed by any token of this type; a given token of the type cannot be deprived of any of these properties, unless by accident, or . . . unless through the action of prohibiting external causes.8 Brunschwig understands the claim that the gods exist by nature to mean that tokens of the divine type must exist for the most part or most of the time. It may be that there are no such tokens now or at certain times in the past or future, but it cannot be the case that at no time in the past did any token of the gods exist. On this interpretation of natural existence, D2 is a true conditional.

Th ere is, however, one major problem with Brunschwigs reconstruc-tion that seems to be a decisive objection against it. It is dicult to see

7) Brunschwig, 185. 8) Brunschwig, 186.



how Diogenes could deny that the sages exist by nature, which is some-thing that Diogenes does in Brunschwigs interpretation.9 For Diogenes could not have held that one may not reasonably honour the sages. If he did, then he could have very easily dismissed the parody argument by refusing to give his assent to B1 rather than reformulating premise A2 of Zenos argument. But if Diogenes wanted to maintain that one may reasonably honour the wise, he would have to believe that the wise exist by nature, since Diogenes reformulated premise, C2, commits him to the belief that things that do not exist by nature are not worthy of honour.

Now it is true that some Stoics attempted to discharge the parody argument by appealing to the ambiguity of the word or to hon-our.10 To honour may mean either to worship or to hold in esteem. Th ese Stoics took A1 to mean that one may reasonably worship the gods. B1 would be false if to honour means to worship, but would be true in the second sense of honour. So either B1 is false or the parody argument commits a fallacy of equivocation by using honour in the sense of holding in esteem in B1 and in the sense of worship in B2. Th e reasoning behind this may be that one can reasonably hold in esteem or think highly of ctional characters though it would be absurd to wor-ship them.

Diogenes did not invoke the ambiguity of honour but instead seems to have held that while the gods exist because they exist by nature the natural existence of the wise does not entail their actual existence. Th e question then is what the relevant distinction between the gods and the wise is. If Diogenes believed that the wise exist by nature, then exis-tence by nature cannot mean normal existence or existence most of the time. Th ere does seem, however, to be good reason to believe that something has a property F by nature if it has or will come to have that

9) See Brunschwig, 187-9. E1 is a . According to DL 7.71, a - (which is distinguished by the use of rather than the of simple conditionals) asserts that (i) if p, then q, and (ii) p is true. Brunschwig argues that in denying E1, Diogenes is denying both (i) and (ii). In my reconstruction, Diogenes only denies (i), not the truth of the antecedent. Th at is, Diogenes denies that the sages pres-ent existence follows from their natural existence but accepts their natural existence. 10) See M 9.136.



property whenever external circumstances do not prevent it from being F. Support for this understanding of having a property by nature is found in Sextus treatment of the Stoic theory of signs. Sextus says that the Stoics divided the non-evident () into the absolutely non-evident, the naturally non-evident, and the temporarily ( ) non- evident (M. 8.145). Th e temporarily non-evident are those things that are naturally evident ( ) but are non-evident to us at certain times due to external circumstances ( ). Th e example given is the city of Athens, which is not evident to us because of our distance from it. It is important to note that Athens could remain non-evident to us most, if not all of the time, if we never go near it. In this case, of course, the property is relational, so that Athens is evident to those in or near it, but non-evident to those of us who are far away from it. But the same point would hold in the case of non-relational properties such as existence or wisdom. Th ings exist by nature or are wise by nature if they either do come to exist or become wise except when external circumstances prevent them from existing or being wise. Th is is the sense of natural existence that I wish to defend as the one used by Diogenes. Th is understanding of natural existence is preferable to Brunschwigs because it allows us to arm that sages are worthy of honor and to deny that sages exist most of the time.

My understanding of natural existence faces its own diculty, however, because if it is correct, the Stoics would have had to believe that the development of a sage is natural and that only external circum-stances could prevent a human from becoming a sage. Can such a view be attributed to the Stoics?

Th ere is support in a number of Stoic sources for attributing to the Stoics the doctrine that wisdom is the natural result of normal human development and that the ability to become a sage is naturally implanted in all humans.11 According to these sources, human development to wisdom is natural in the same way that it is natural for seeds to develop into mature plants. But the claim that wisdom is a natural feature of

11) Th is discussion of the naturalness of the development of wisdom is heavily indebted to Jackson-McCabe (2004). I am grateful to a referee of this journal for drawing my attention to Jackson-McCabes paper.



human development is nevertheless consistent with the rarity of wise people, just as it is natural for a seed to develop into a full-grown organ-ism even if very few seeds actually do so because their natural develop-ment is often frustrated or prevented by external conditions.

In particular, Plutarch notes that Chryippus said that his teaching concerning good and bad things connects especially with innate or implanted preconceptions ( ).12 Th ese implanted preconceptions, Jackson-McCabe has argued, are mentioned by Chrysippus in reference to preconceptions of the ethical sphere whose formation is guaranteed by oikeisis, and which in this sense represent a type of inborn knowledge (327). It is oikeisis that is responsible for the ability of animals to distinguish between what is benecial and harmful to their constitutions. In humans, that tendency is conjoined with rea-son and the ability to form concepts, so that humans are endowed with the natural tendency to form concepts of what is good and bad. As Cicero points out, once man possesses understanding or the ability of conception (intellegentiam vel notionem potius), he will ultimately by exercise of intelligence and reason come to grasp the concept of good-ness in itself, that is, what is praiseworthy and desirable for itself (per se laudandum et expetendum).13 Th us, the formation of the moral con-cepts and their discernment is a natural process that results from the combination of oikeisis and rationality that is characteristic of human nature.

Seneca makes explicit the seed analogy by noting that nature has given us the seeds of knowledge (semina nobis scientiae dedit),14 seeds which by their nature result in knowledge though they often will not reach their natural end. Since it is the possession of knowledge that characterizes the sage, it follows that the Stoics believed that sages exist by nature, as understood according to my proposed sense of natural existence.

My interpretation of natural existence faces a further problem because although Brunschwigs interpretation of existence by nature clearly

12) Plutarch, De Stoicorum repugnantiis, 1041E. 13) Cicero, De nibus, 3.21 (Rackham) 14) Seneca, Ep. 120.4.



makes the conditional D2 true, my interpretation does not. It does not follow from the fact that something exists by nature that it existed some time in the past, since external circumstances may always have pre-vented it from existing. If my interpretation is correct then it must make D2 true without making the general inference from existence by nature to existence once upon a time licit. Fortunately, there is a way to do this. Th e argument assumes that part of the concept of god is being ungenerated and indestructible. It may also be part of the concept of the divine that it is impassible it cannot be aected by external causes or at least cannot be prevented by external causes from having the qual-ities to which it has an appropriate relation. Th is is, of course, true of the Stoic god. Th e Stoic god is identied with the active principle of the universe, the designing re that creates and sustains the world.15 Since the only other principle recognized by the Stoics is the passive and inert matter, there are no causes or inuences external to god. Th erefore, if the Stoic god exists by nature, it will exist, because there are no external circumstances that can prevent it from existing. In contrast, sages also exist by nature but because there are external circumstances that can prevent humans from becoming sages, the natural existence of sages does not entail their actual existence.

Another objection to my interpretation is that it does not make sense of the way in which Diogenes tries to show that the gods natural exis-tence implies the gods actual existence. If the gods exist by nature and there are no external circumstances that could prevent them from exist-ing, then it should be obvious that the gods must exist now. Why, then, does Diogenes only infer from the gods natural existence that the gods existed at some time in the past, and then bring in D1 to draw the desired conclusion? Perhaps Diogenes was anticipating a potential objection along the following lines. One could object to Diogenes that the mere fact that something exists by nature and is not prevented by external circumstances from coming into existence does not entail that that thing will immediately come into existence. For example, the Stoic cosmos by nature results in a state of conagration. Further, no external circumstances prevent the conagration from coming into existence. But the nature of the cosmos is such that it gradually develops into this

15) See, for example, DL 7.134.



state. It is understandable that the word for nature, , which derives from , to grow, would be associated with processes of develop-ment and unfolding. Th us, the natural existence of the gods (and the absence of external constraints) would not necessarily imply the gods present or actual existence but at best only a process of development that would result at some time in the existence of gods. Accordingly, the move from the gods natural existence to the gods actual existence needs further support.

Th at support comes from the conceptual understanding of the gods as ungenerated and indestructible beings. If we add these two charac-teristics to the divine nature, then the desired result follows. Diogenes complete argument may be reconstructed as follows.16 Th ere are two auxiliary arguments whose conclusions are used in the main argument to get to the nal conclusion that the gods exist now. Th e rst auxiliary argument is

I1: If the gods are impassible, then nothing can prevent the gods from existing.

I2: Th e gods are impassible according to their conception. [a basic tenet of Stoic physics, in which god or re is the active principle and matter is the passive principle]

I3: Th erefore, nothing can prevent the gods from existing. (I1 and I2 by the Stoics rst indemonstrable or modus ponens)17

16) Th e reconstruction is much more complex than the argument as reported in Sex-tus, but Sextus account is clearly truncated. Th e point of my reconstruction is to make explicit all the assumptions and logical inferences Diogenes would need to reach his conclusion from the given premises. 17) In reconstructing the argument it is important to make only those inferences known to be acceptable to the Stoics. It has been convincingly argued that Stoic logic is a form of relevance logic in which many sequents that are valid in classical logic do not hold (see Bobzien (1996), 185f.). I use Bobziens account of Stoic inference to show that the Stoics would have accepted this reconstructed argument as valid. Accordingly, arguments must either be one of the ve indemonstrables or be capable of reduction to one of the indemonstrables using only the four Stoic themata. See Bobzien (1996), 134-141 for a discussion of the indemonstrables, and 143-163 for the themata.



Th e second auxiliary argument is

H1: If the gods are not of such a nature to exist, then one may not rea-sonably honour them.18

H2: One may reasonably honour the gods. [A1 of Zenos argument] H3: Th erefore, the gods are of such a nature as to exist. (H1 and H2 by

the second indemonstrable or modus tollens)

Th e main argument begins by using the rule of addition19 to form a conjunction from I3 and H3:

M1: Th e gods are of such a nature as to exist and nothing can prevent the gods from existing.

Given our understanding of natural existence, the following condi-tional must be true:

M2: If the gods are of such a nature as to exist and nothing can prevent the gods from existing, then the gods must exist either in the past but not now or in the future but not now or the gods must exist now.20

M1 and M2 entail

M3: Th e gods must exist either in the past but not now or in the future but not now or the gods must exist now.

18) Th is is an instantiation in conditional form of the general principle C2 of the original argument. Th e reformulation as a conditional is necessary in order for this argument to be in the form of the second indemonstrable. 19) Th e sequent A, B A and B is valid in Stoic logic. Application of the rst thema (for which, see Apuleius, Int. 209.12-14) reduces this sequent to the third indemon-strable (for which, see M 8.266 and DL 7.80):

not(A and B), A not B 20) Th e Stoic or is exclusive (see Gellius, Noctes Atticae, 16.8.12-14). Th e disjunction X exists in the past or X exists in the future can be false in Stoic logic since both dis-juncts can be true. In order for M2 to be a sound conditional, the consequent must be formulated as above.



By denition of destruction and generation we can assume

M4: If the gods exist in the past but not now, then they have been destroyed.

and

M5: If the gods exist in the future but not now, then they will be generated.

But according to their conceptions,

M6: It is not the case that the gods are destroyed.

and

M7: It is not the case that the gods are generated.

M4 and M6 entail by the second indemonstrable

M8: It is not the case that the gods exist in the past but not now.

and M5 and M7 likewise entail

M9: It is not the case that the gods exist in the future but not now.21

We can combine M8 and M9 to get

M10: It is not the case that either the gods exist in the past but not now or that the gods exist in the future but not now.22

21) Th e account in Sextus must be abridged here, giving premise M8 but not M9 and thus not explaining the relevance of gods ungenerated nature in the argument. 22) A valid move in Stoic logic since not A, not B not (A or B) can be reduced to the fth indemonstrable A or B, not A B by one application of the rst thema. For the fth indemonstrable see DL 7.81.



Finally M10 and M3 take us to the desired conclusion again by means of the fth indemonstrable:

M11: Th e gods exist now.23

As it stands the reconstruction makes use only of principles that are attributed either to Diogenes or the Stoics or which they in general would accept, and all the inferences are valid in Stoic logic. Th e argu-ment reconstructed in this way has the advantage over Brunschwigs reconstruction because it allows us to explain why Diogenes reinter-preted Zenos argument in light of the parody in his own way rather than simply discharging the parody by pointing out the ambiguity of honour. Further, my reconstruction, unlike Brunschwigs, does not attribute to Diogenes the belief that the sages are not worthy of honour.

II. Natural Possibility and Hellenistic Modal Logic

Having presented the reconstruction, we turn now to the conception of possibility that Diogenes uses in the argument and its relation to the other modal concepts in Hellenistic logic. One of the reasons that Dio-genes argument is so interesting is that it may help to shed light on the development of modal logic in the post-Chrysippean Stoa, and in par-ticular, to provide evidence of the continued use of older, pre-Chrysip-pean modal concepts among the Stoics. Th e concept of being of such a nature as to exist, which plays a central role in the reconstructed main argument, seems to be a special form of a modal concept, namely a form of possibility according to which something is possibly F if it will come to have that property F whenever external circumstances do not prevent it from having F. Let us refer to Diogenes conception of pos-sibility as natural possibility.

Natural possibility closely resembles the denition of possibility attributed to the dialectician Philo:24

23) Th at is, (A or B) or C, not (A or B) C, which is a substitution instance of the fth indemonstrable. 24) Alexander, An. Pr. 184, 9-10. See also Boeth., Int. 234, 10-21 and Simplicius, Cat.



[the possible] is this: what is said of the subject according to its bare tness ( ), even if it has been prevented from coming to be by some external necessity ( ). Accordingly Philo said that it is possible that cha lying in the uncut [wheat] ()25 or in the depth of the sea be burned where it is, even though by necessity it is prevented by its surrounding.

Th is Philonian possibility must be contrasted with the Stoic denition of possibility usually associated with Chrysippus. For Chrysippus a possible proposition is that which admits of being true and external factors ( ) not preventing it from being true.26 According to Chrysippus, it is not possible that the cha at the bottom of the sea burn, since it is prevented by external circumstances from burning. Th erefore the conception of possibility (i.e. being of such a nature as to be F) that Diogenes uses in his argument is closer to the Philonian conception of possibility, since for Diogenes the wise man is of such a nature as to exist even though external circumstances may always pre-vent him from existing. Let us refer to Diogenes conception of possi-bility as natural possibility.

Is natural possibility the same as Philonian possibility? Th eir identity would make sense on the very plausible assumption that Diogenes is arguing with Alexinus, who belonged to the same school as Philo.27

7, 195f. It should be noted that this modal denition, like the Stoic ones, is de dicto. Th at is, a proposition is possible just when the very nature of the statement is sup-portive of truth, as Boethius puts it, even if factors extrinsic to the proposition prevent the proposition from being true. But presumably the reason why propositions like I will read Th eocritus Bucolica today and Cha burns are possible is because of a de re possibility or suitability possessed by the referent of the subject. Th us, Simplicius notes that on the oor of the ocean a piece of wood is combustible as far as it is in itself and according to its nature ( ). Note that both Boethius and Sim-plicius characterize Philonian possibility in terms of the nature of either the statement or object in question. 25) Following the translation in Alexander (1999), 94 rather than Long and Sedleys atomic dissolution (LS 38B2). 26) DL 7.75. See Frede (1974), 107-117 and Bobzien (1993), 76-84 for discussion of this denition. 27) DL 2.109. Philo was a student of Diodorus (DL 7.16), who was a student of Apol-lonius, himself a student of Eubulides (DL 2.110). According to DL 2.109, Alexinus was among the successors of Eubulides ( ).



Since Diogenes is arguing dialectically, it is understandable that he would make use of a modal denition propounded by a colleague of Alexinus, and therefore likely to be the one accepted by Alexinus.28 Although the sources are too meager to warrant certainty, the combina-tion of three considerations (the use of in the accounts of both Philonian possibility and natural possibility, the fact that Diogenes argument emerges from dialectical engagement with a member of the same school as Philo, and the fact that the interpretation of natural existence as a Philonian modality allows for a more plausible recon-struction of Diogenes argument than does Brunschwigs interpreta-tion) makes it highly likely that natural possibility is essentially Philonian possibility.29

28) Th ere is reason to suppose that some of the pre-Chrysippean Stoics also accepted the Philonian modalities. Th e early Stoa generally inherited the logical doctrines of the Dialecticians: Zeno studied logic under Diodorus and Philo (DL 7.16), and according to Cicero, Zeno contributed much less to the development of logic than previous philosophers (Gell. 7.2.6-13). Frede and Ebert both provide support for the depen-dence of pre-Chrysippean Stoic logic on the Dialecticians by noting the several paral-lels between the titles of logical books written by Cleanthes and his disciple Sphaerus and the titles of books by Diodorus and Philo (Frede (1974), 22; Ebert (1987), 107-8). It is likely, therefore, that the Stoic logicians prior to Chrysippus did not make any signicant advances beyond the logic of the Dialecticians. Th e two Dialectical modal denitions are those of Diodorus and Philo. Since Cleanthes rejected Diodorus Master Argument, which was used by Diodorus to support his denition of the modal con-cepts, and rejected the necessity of the past (see Epictetus 2.16.5), he presumably accepted the Philonian denitions because true propositions about the past are always necessary under the Diodorean denition of necessity but not under the Philonian denition. For the Philonian modalities are concerned solely with the intrinsic features of the proposition, and the passage of time is an extrinsic factor that by itself would not alter the Philonian modal status of a proposition. If Zeno also accepted Philos denition, there is another reason why Diogenes would invoke Philonian possibility. Since Diogenes is attempting to recon struct Zenos thinking to defend the argument against the parody, he is obliged to use the denition of possibility available to Zeno. 29) Brunschwig (p. 186) seems to hint at the relation of natural existence to Philonian possibility though he does not make an explicit connection: cups are of such a nature as to be broken; they normally break, unless one or even lots of them have sunk in the depths of sea.



III. Is Diogenes Argument an Ontological Argument?

We can now turn to the question of whether Diogenes argument as reconstructed is an ontological argument. One of the diculties in deciding whether an argument is ontological is the obscurity of the criteria usually used to dene such arguments. Th e term, of course, is due to Kant, who dened ontological arguments as those that abstract from all experience, and argue completely a priori, from mere concepts, to the existence of a supreme cause.30 It is often dicult, however, to determine when an argument argues completely a priori or from mere concepts. Th is requires that we be able to distinguish between proper-ties that are part of the concept of God (or the gods) and those that are not. Th us Zeno, whose argument for the existence of the gods Dio-genes tried to salvage from parody, used the premise One may reason-ably honour the gods. Is the property reasonably honoured part of the concept of the gods, something that may be inferred a priori without any reference to empirical considerations? One may plausibly argue that claims about reasonableness are matters of prudential consider-ation dependent upon empirical facts about human nature and not simply upon some conceptual truths about the gods. Alternatively, one could maintain that being worthy of honour pertains to the gods inde-pendent of whether honouring them has good consequences for humans. If one follows the Kantian denition alone, the question of whether an argument containing such a premise is ontological cannot be conclusively answered.

Perhaps a better way to proceed is to look at some later versions of ontological arguments and determine if there are any such arguments that resemble the argument forms of the Stoic arguments. Useful in this regard is Graham Oppys taxonomy of ontological arguments. Oppy divides ontological arguments into seven categories: denitional, con-ceptual, modal, Meinongian, experiential, mereological, and Hege-lian.31 In general Oppy prefers to characterize ontological arguments as those that proceed from considerations that are entirely internal to the theistic worldview. Th at is, the premises of ontological arguments

30) Kant (1929), 500. 31) Oppy (1996), 1.



involve terms that non-theists would object to if used in contexts that bestow existential import upon those terms, examples of which include greatest possible being, beings than which nothing greater can be con-ceived, and most perfect being. Ontological arguments use such terms, but in order to avoid circularity the terms that appear in the premises must fall outside of ontologically committing contexts.

Diogenes argument appears to resemble most closely the modal arguments. Th is is not surprising given the rich tradition of modal logic that preceded Diogenes both within the Stoa and in the work of the Megarians and Dialecticians such as Diodorus Cronus.32 Modal onto-logical arguments are arguments with premises that make modal claims about God, claims involving the possibility or necessity of Gods exis-tence.33 An example would be

It is possible that God exists. Either it is impossible that God exists or it is necessary that God

exists. It is necessary that God exists. Th erefore, God exists.

Applying ancient denitions of the modal operators, it is easy to con-struct an ancient modal ontological argument. For example, Diodorus held that the possible is what either is or will be true.34 Given this denition of the possible, one can easily imagine Diodorus arguing in this way:

1. It is possible that the gods exist. 2. It is true or will be true that the gods exist. (by 1 and Diodorus

denition of the possible)

32) Th ere is disagreement about the existence of a Dialectical school and its relation to the Megarians. I follow Sedley (1977) in arming the existence of a distinct Dialecti-cal school though the main theses argued for here do not depend on acceptance of Sedleys views. 33) Examples of modern versions of such modal ontological arguments can be found in Malcolm (1960) and Plantinga (1974), 196-221. 34) Epictetus, Diss. 2.19.1-5 (Schenkl); Boethius, Int. 234, 22-6 (Meiser).



3. If it will be true that gods will exist, then gods exist at all times (because the gods are not of such a nature as to come into exis-tence or go out of existence).35

Th erefore the gods exist now.

We would not have any trouble identifying this as a modal ontological argument since the argument has premises that make modal claims about the gods in a similar way that modern modal arguments do about God. Diodorus has his own peculiar temporal analysis of modal con-cepts but his conceptions of these concepts are still recognizable as cor-responding to modern conceptions of possibility and necessity.

Of course there is no evidence that Diodorus actually formulated such an argument. Pace Gilson, however, there is no reason to think that Diodorus could not have dreamt of producing this argument. We do have, though, the actual argument of Diogenes as reported by Sex-tus Empiricus, and I think that Diogenes argument is best understood as a modal ontological argument, since, as I have argued, Diogenes makes use of a modal concept resembling Philonian possibility.

Before making the case that Diogenes argument is a modal onto-logical argument, however, it is necessary to dispose of one possible objection to considering an ancient argument like Diogenes as an ontological argument. Th e most obvious dierence between the ancient arguments and modern ontological arguments is that the Stoic argu-ments are arguments for the existence of gods, not of God. But this is only an apparent dierence once one sees that the Stoics were mono-theists who veiled themselves as polytheists. For although the Stoics used the names of the traditional gods, it is clear that these names describe dierent features of, and were intended to refer to the one god that the Stoics identied with the cosmos:

[God] is called by many names according to his powers. For they call him Zeus () through whom ( ) all things come to be. Th ey call him Life () in so far as he is the cause of life or extends all through life, and Athena with respect to the extension of his commanding-faculty into the ether ( ), and Hera with respect to its extension into the air ( ). (DL 7.147)

35) A principle that is appealed to in Diogenes argument. See Sextus Empiricus, M 9.135.



Th ere is also evidence concerning Diogenes own inclination to allego-rize things commonly taken to be divine. Cicero states that Diogenes of Baby lon . . . in his book Minerva rationalizes the myth of the birth of the virgin goddess from Jove by explaining it as an allegory of the pro-cesses of nature.36 Minucius Felix wrote that Diogenes of Babylon again adopts a similar school of teaching in expounding the birth of Jupiter, the pro duction of Minerva and the like, as terms denoting things, not gods.37 Although Diogenes argument concludes that the gods exist, we should read this to mean that the one Stoic god that can be described in numerous ways exists. I will use the term god to refer to the one Stoic god the establishment of whose existence is the real purpose of Diogenes argument. God is reserved for the supreme being of classical theism, the God of Anselm. In the reconstruction of the propositions forming the ancient arguments I retain the plural form but add the proviso that it is a simply a manner of speaking.

Returning to the question of whether Diogenes argument meets the criteria Oppy proposes for ontological arguments, recall that for Oppy ontological arguments are arguments that proceed from considerations that are entirely internal to the theistic worldview. It seems that Dio-genes argument is ontological in this sense. Diogenes makes use of concepts that are internal to Stoic theology, specically the impassible, ungenerable, and indestructible nature of the Stoic god and then pro-ceeds from these concepts to derive the existence of that god now.

Accordingly, Diogenes argument would be a form of the modal ontological argument that uses the natural possibility of the gods exis-tence to infer their current existence. As in other modal ontological arguments, the special attributes of god ensure that god must exist given natural existence while the inference from the natural existence of other things (such as sages) to their actual existence is blocked.

Th ere remains, however, another reason to doubt that Diogenes argument is ontological. Th e natural existence of the Stoic god is not part of the idea of god but follows from a normative claim about the propriety or rationality of humans honouring gods. Th e auxiliary argu-

36) Cicero, De natura deorum, 1.15 (Rackham). 37) Minucius Felix, Octavian, 19.12 (Rendall).



ment I1-3 is not based on a conceptual truth about god internal to theology but on what it is reasonable for humans to do.

One should rst note that the premise that one may reasonably hon-our the gods can be read in two ways. An anthropocentric reading interprets the premise to say that it is reasonable to honour god on prudential or pragmatic grounds. It is not that god is intrinsically hon-ourable but, reasoning along the lines of Pascals wager, the safer policy for humans is to behave as if there is a god.38 A theocentric reading understands the premise to be making a claim about the intrinsic nature of the god. God is by nature worthy of honour.39 Barnes and Bett sup-port a theocentric reading while Brunschwig and Schoeld advocate an anthropocentric reading. In the case of an anthropocentric reading, the premise is not internal to Stoic theology but one that is more widely acceptable on strictly prudential grounds. Likewise, if the premise is read anthropocentrically, then it would be a normative claim about rational human behaviour involving empirical considerations rather than a conceptual truth about god. In either case such a reading would prevent the argument from being purely ontological.

As Bett points out,40 an anthropocentric reading of A1 would make Zenos premises obviously inconsistent and thereby make his argument unsound. For if the reason that one may reasonably honour god is that ones failure to honour god may result in dire consequences should god exist, then honouring non-existing things may be reasonable as long as one does not know for certain that they do not exist. Bett notes that there are no good prudential reasons for honouring beings that are known not to exist. But even that can be questioned. If it is reasonable to honour gods because it is safer to follow convention than to out it, it may be reasonable even to honour things that one knows do not exist. But A2 denies the reasonableness of honouring non-existing things. So the reasonableness of honouring some non-existing things is entailed by A1 on the anthropocentric reading and denied by A2. Th e theocentric reading does not face this problem since the claim that the gods are by their nature worthy of honour does not entail that it is

38) See Brunschwig, 175 and Schoeld, 38-39. 39) Barnes (1972), 17. 40) Bett (1996), 85-86.



reasonable to honour non-existing things. Th e theocentric reading of A1 is, therefore, more plausible. Further, since Sextus report does not state that Diogenes altered Zenos rst premise, one may assume that Diogenes reading of A1 is the same as Zenos.41

However, regardless of whether one accepts the theocentric or anthro-pocentric reading of this premise, the status of Diogenes argument as a modal ontological argument should not be aected. Th e reasonableness of honouring god is invoked simply to arrive at the possibility of gods existence. Once the possibility is established, the main argument is used to infer the actual existence of god. It should not matter that the auxil-iary argument makes use of empirical or prudential considerations. Suppose that one presented a modal ontological argument in which the possibility of Gods existence is used to infer the necessity of Gods exis-tence. In order to support the possibility of God, the arguer uses some empirical or psychological fact (that humans do conceive of God) and then adds the premise that whatever one conceives of existing can exist. Th e use of such an argument in support of the possibility of Gods exis-tence would not call into question the ontological character of the main argument. Neither then should the auxiliary argument of Diogenes, if indeed it contains an empirical premise, undermine the ontological character of his main argument.42

If this is correct, then Diogenes main argument is a modal onto-logical argument because its premises are purely conceptual claims about god internal to Stoic theology and a modal concept plays a cen-tral role in the argument. Th ere is, however, an important distinction between Diogenes argument and Anselms argument. Anselms argu-ment is much simpler, making use only of one feature of God (that He is that than which nothing greater can be conceived) and deriving all other attributes (e.g. eternity and impassibility) as corollaries.43 Th us,

41) Cf. Bett, 87. 42) Whether Zenos argument is ontological or not does depend on the interpretation of A1, since this premise is an essential part of his argument. Even if Zenos premise should be taken theocentrically, Zenos argument is at best a crude rst attempt at an ontological argument, and credit is due to Diogenes for constructing a more sophisti-cated and rigorous proof. 43) Anselm demonstrates the impassibility of God in chapter 8 of the Proslogion and eternity in chapter 13.



while Diogenes argument is ontological, it lacks the simplicity, ele-gance, and power of Anselms argument. Gilsons claim that no trace of the ontological argument exists in Greek thought cannot be sustained in the light of Diogenes argument, though it remains true that Anselm went beyond ancient thought by arguing from the mere idea of God as that than which nothing greater can be conceived to the conclusion of Gods necessary existence.44

References

Alexander of Aphrodisias (1999) On Aristotle Prior Analytics 1.14-22, translation by I. Mueller (London).

Barnes, J. (1972) Th e Ontological Argument (London). Bett, R. (1996) Hellenistic Essays Translated, Apeiron 29, 75-97. Bobzien, Susanne (1986) Die stoische Modallogik (Wrzburg). (1993) Chrysippus Modal Logic and Its Relation to Philo and Diodorus, in

Dring and Ebert (eds.), Dialektiker und Stoiker (Stuttgart), 63-84. (1996) Stoic Syllogistic, Oxford Studies in Ancient Philosophy 14, 133-192. Brunschwig, J. (1994) Papers in Hellenistic Philosophy, translation by J. Lloyd

(Cambridge). Dring, K. and Ebert, T. (eds.) (1993) Dialektiker und Stoiker (Stuttgart). Ebert, T. (1987) Th e Origins of the Stoic Th eory of Signs in Sextus Empiricus, Oxford

Studies in Ancient Philosophy 5, 83-126. Frede, M. (1974) Die stoische Logik (Gttingen).Gilson, . (1936) Th e Spirit of Medieval Philosophy (Notre Dame). Jackson-McCabe, M. (2004) Th e Stoic Th eory of Implanted Preconception, Phrone-

sis 49, 323-347. Kant, I. (1929) Critique of Pure Reason, translation by N.K. Smith (New York). Long, A.A. and Sedley, D.N. (1987) Th e Hellenistic Philosophers (Cambridge). Malcolm, N. (1960) Anselms Ontological Arguments, Philosophical Review 69,

41-62. Oppy, G. (1996) Ontological Arguments and Belief in God (Cambridge). Plantinga, A. (1974) Th e Nature of Necessity (Oxford). Schoeld, M. (1983) Th e Syllogisms of Zeno of Citium, Phronesis 28, 31-58.

44) I am grateful to Richard Bett, Henry Dyson, Steven Strange and an anonymous referee of this journal for their comments on earlier drafts of this paper.


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