Richard Bett

Aenesidemus the Anti-Physicist

Sextus wrote at considerable length about physics; we have two sizeable books of his that are now usually called Against the Physicists (M9–10), and more than half of the final book of Outlines of Pyrrhonism (PH 3) covers roughly the same ground as these two books, albeit more briefly. According to Sextus, Pyrrho’s disciple and biographer Timon also wrote a book or books called Against the Physicists (M 3, 2). The point that Sextus says he is borrowing from this work has to do with the legitimacy or otherwise of proceeding from hypotheses, which (however congenial in general terms to Sextus’ own Pyrrhonist outlook) has nothing specially to do with physics. But there is no reason to doubt the ascription, and in fact Sextus gives other evidence of an interest in physical topics on Timon’s part; in his own Against the Physicists, and again in Against the Musicians, he attributes to Timon the assertion that no process divisible into parts, such as coming into being, perishing or the like, can take place in a time that itself has no parts (M 10, 197, M 6, 66). A fragment of Timon’s own verse about Pyrrho, quoted in Diogenes Laërtius (9, 64–65), seems to suggest (and to regard as a reason for praise) that Pyrrho did not concern himself with questions about the nature of the world around us; if so, Timon’s own involvement in physics may represent a departure from Pyrrho, and perhaps also a development in his own thinking. But there are in any case reasons for thinking that Timon did not simply parrot his teacher (if that is what Pyrrho should be called).

I mention these points in order to prepare for the thought that it would be in no way surprising if Aenesidemus – the founder of the sceptical movement to which Sextus later belonged, a movement that regarded itself as “philosophizing in the manner of Pyrrho” (Phot. Bibl. 169b26–27), but presumably relied above all on the writings of Timon for its understanding of what that meant – would also have engaged in discussion about topics in physics. One would not, of course, expect Aenesidemus to have offered physical theories of his own; rather, as a sceptic, he would be expected to have the goal of subverting confidence in the physical theories of others. And this is precisely what the evidence, limited as it is, suggests.

We do not hear of a book of Aenesidemus called Against the Physicists. But among the various sets of Modes summarized by Sextus is a set of eight Modes attributed to Aenesidemus and devoted to undermining all attempts at αἰτιολογία, causal explanation (PH 1, 180–186). In both the Stoics’ and Sextus’ divisions of philosophical subject-matter (D.L. 7, 132, PH 3, 13, M 9, 195), causation comes under physics; besides, a mention of “elements” (στοιχεῖα, PH 1, 183) in the course of Sextus’ extremely bare account of these Modes indicates that they were directed particularly against explanations in physics.

In addition, the summary of Aenesidemus’ Pyrrhonist Discourses (Πυρρώνειοι λόγοι) in Photius (Bibl. 169b18–171a4) makes clear that a substantial portion of that work concerned physical matters, and that the purpose throughout was to create trouble for anyone trying to fashion positive theories in this area. After an overview of the main points of the first book, which appears, like the first book of Sextus’ PH, to have been a general account of the Pyrrhonist outlook, Photius gives one-sentence summaries of the contents of each of the other seven books. The last three books had to do with ethical topics; but for each of the second to the fifth books Photius includes topics in physics, even if these are sometimes juxtaposed with topics that, at least in Sextus, count as part of logic (170b3–22). The second book, according to Photius, concerned (besides truth, a logical issue) causes and effects, motion, coming into being and perishing, “and their opposites” (170b6–7 – it is not clear what this might mean except as applied to motion). The third book dealt, again, with motion (in addition to sense-perception). The fourth book had to do with signs, which for Sextus, at least as a topic in its own right, falls under logic; but signs may of course be made use of in physical inquiry, and Photius also includes as part of the subject-matter of this book “the typical sequence of impasses about the whole of nature and the universe and the gods” (170b15–16). Finally, the fifth book is again said to deal with causes, attacking those who engage in αἰτιολογία; Photius also refers here to a set of Modes on this subject that are, we may assume, the same ones run through so telegraphically by Sextus.

To this we can add that Sextus’ own Against the Physicists contains a few mentions of Aenesidemus. In some cases the reference is to “Aenesidemus in accordance with Heraclitus” (M 9, 337; 10, 216, cf. 233), and the question of what this means, and what such references can allow us to infer about Aenesidemus’ own views, is a notoriously difficult one.331 But we are also told of an argument employed by Aenesidemus to the conclusion that “nothing is a cause” (M 9, 218–226); there is no obvious connection with the styles of argument in the eight Modes concerning causation, but this further testifies to Aenesidemus’ interest in the topic. Besides this, we are told that Aenesidemus employed a twofold distinction among types of motion (M 10, 38) – presumably in order to mount a critique of other philosophers’ theories of motion, although this is not specified.

So we need not doubt that Aenesidemus involved himself in arguments about topics in physics. But now, was space or place one of these topics? I am not aware of any arguments about space or place specifically attributed to Aenesidemus by name, but the supposition is likely enough. We know from both Photius and Sextus that Aenesidemus dealt with the topic of motion (at some length, if its appearance in two different books in Photius’ catalogue is to be believed). And in Sextus’ Against the Physicists, the topic of motion comes immediately after that of place, while in the physical portion of PH place comes immediately after the various species of motion (in the broadest sense) plus rest. We should not, of course, assume that Aenesidemus treated his topics in the same order as Sextus does his; and in fact, Photius’ catalogue suggests a rather different order of topics from either of Sextus’, guided by no clearly discernible principle. But in both works of Sextus, the juxtaposition of motion and place is not merely accidental; there is an obvious conceptual connection between the two topics – if motion occurs, there must be such a thing as the place in which it occurs –and in both works he alludes to this in making the transition between them (M 10, 36, PH 3, 118). Given this connection, it is hard to believe that Aenesidemus, too, was not led to discuss place at least in the course of his discussions of motion – especially since one of the two types of motion that Sextus says Aenesidemus distinguished was “transitional motion” (, M 10, 38. 41), i. e., motion from place to place.

This, of course, does not take us very far. Can we get any closer to a sense of what Aenesidemus might have said about space or place? One of the Ten Modes, summarized somewhat differently by Sextus and Diogenes Laërtius and made use of or alluded to by several other authors, has to do with, in Sextus’ description, “positions and intervals and places” ( τóπους, PH 1, 118), and in Diogenes’, with “distances and what kind of positions and places” (τὰς ἀποστάσεις καὶ ποιὰς θέσεις καὶ τοὺς τóπους, 9, 85 – Diogenes adds “and the things in the places”, but as Annas and Barnes point out, this seems not to contribute anything significant).³³² Now, the Ten Modes have usually been regarded as deriving from Aenesidemus; not in the sense that he invented them from scratch – for, as is well known, much of the material in them can be traced back centuries before his time – but in the sense that he compiled this material into a systematic scheme of argument to be used for specifically sceptical purposes. Since Aenesidemus’ authorship of the Ten Modes has been questioned in recent times,³³³ I think it is worth rehearsing the reasons why the attribution is fundamentally sound.

In the surviving summary of the Ten Modes in Sextus, he ascribes them not to Aenesidemus, but to “the older sceptics” (PH 1, 36), by contrast with the “younger sceptics” (PH 1, 164) to whom he ascribes the Five Modes; since the terms “older sceptics” and “younger sceptics” have no precise reference, this tells us nothing beyond a relative chronology of the two sets. But in Against the Logicians (M 7, 345), during a mention of the deceptiveness of the senses, Sextus adds the following back-reference: “as we showed in going over the Ten Modes of Aenesidemus”. Now, as Karel Janáček showed in his seminal article “Die Hauptschrift des Sextus Empiricus als Torso erhalten?”,³³⁴ the books that we now know as Against the Logicians, Physicists and Ethicists are the surviving portions of a work that must originally have included an opening, general treatment of Pyrrhonism, occupying the same status as PH 1 does in relation to PH 2 and 3; it is likely, then, that Sextus is referring back to a version of the Ten Modes in this lost part – that is, earlier in the same work – rather than to the version in PH 1. But either way, there is no reason to doubt the plain significance of Sextus’ phrase “the Ten Modes of Aenesidemus”; and this is confirmed by the reference to Aenesidemus’ Modes in the critique of Pyrrhonism by Aristocles of Messene (in Eus. PE 14, 18, 11), who is much closer to Aenesidemus’ own time than is Sextus. Admittedly Aristocles refers to nine Modes, not ten. But there are many possible explanations of this discrepancy, and Aristocles’ description of the content of these modes, compressed as it is, makes clear that what he is attributing to Aenesidemus is a version of the same material that appears as the Ten Modes in Diogenes and Sextus – including an argument based on “distances [ἀποστήματα] and sizes and motions” that looks like the Mode in which we are interested. That we are entitled, then, to think of the Ten Modes as “of Aenesidemus”, in the sense explained, seems clear enough; thus far I am in complete agreement with Emidio Spinelli’s recent discussion in his Questioni scettiche.³³⁵

But there is a little more to add, in confirmation both of a lost treatment of the Ten Modes by Sextus and of Aenesidemus’ involvement with these Modes; here I must acknowledge a debt to David Sedley.³³⁶ At one point in Diogenes’ treatment of the Ten Modes, there is a mention of different orderings of these Modes by different authors; in the course of this Diogenes says: “[t]he ninth [that is, the ninth in his own ordering] Sextus and Aenesidemus put tenth; and the tenth Sextus says is eighth” (9, 87). Now, Diogenes’ tenth Mode, the mode of relativity, is indeed paralleled by the eighth Mode in Sextus’ PH 1 treatment. But the ninth in Diogenes is also the ninth in PH 1, not the tenth. So either someone has made a mistake, or “Sextus and Aenesidemus” refers to a different treatment in the works of Sextus, a treatment in which, unlike in the version that we have, Sextus followed Aenesidemus’ original ordering. Since we already have good reason to believe that there was a lost general portion of Sextus’ longer work, and a general treatment of Pyrrhonism is just where one would expect to find an account of the Modes, I think we may accept the latter hypothesis; and the greater proximity to Aenesidemus in this longer work, as compared with the treatment of the Ten Modes in PH 1, may be taken as an indication that this work was composed earlier than PH, rather than later.

We have, then, two surviving versions of a Mode concerning place and related matters that can reliably be traced to Aenesidemus. It is here, if anywhere, that we can hope to find evidence of how Aenesidemus may have treated the topic of place. The question now is whether it is possible to discern from the surviving versions what Aenesidemus’ own version of this Mode may have looked like. Sextus’ and Diogenes’ versions of the Mode differ considerably, but also share many elements. Sorting out the similarities and the differences is clearly the first step.

As we saw, both Sextus and Diogenes use three key terms to introduce this Mode, but they are not exactly the same. While both have “positions” (θέσεις) and “places” (τóπους), Sextus has “intervals” (διαστήματα) and Diogenes has “distances” (ἀποστάσεις). Both terms seem to have some support from earlier sources. Philo of Alexandria, whose reproduction of the Modes – albeit not under that title, and for a non-sceptical purpose – is the earliest that we have, uses precisely the same three terms as Sextus, in the same order (Ebr. 181). Since Philo is clearly not Sextus’ source, this suggests a version of the Modes circulating prior to Philo – that is to say, not long after Aenesidemus’ own time –on which Philo and, perhaps indirectly, Sextus drew, and in which these three terms formed the label for this Mode. On the other hand, as noted earlier, in what appears to be a brief allusion to this Mode, Aristocles uses the word ἀποστήματα. This may simply be a case of Aristocles reproducing inexactly a text for which he has great contempt, and of which he is in any case giving only a very cursory report. But it could also reflect the presence of a variant term in an early version of this Mode, and if so, Diogenes’ would not be much of a departure from this.

The next question is whether this difference of terminology is of any philosophical significance. Annas and Barnes say that Diogenes’ ἀποστάσεις, “distances”, is “slightly inaccurate”, because not all the examples that fall under this heading have to do with different appearances at different distances; Sextus’ fuller version, they say, has an example in which the differing “intervals” (διαστήματα) are different angles from which something is viewed, not different distances.337 But this seems to me problematic; however, the matter is complicated, and it will take a little while to untangle the issues.

In the example in question, which is indeed grouped with examples involving different διαστήματα, Sextus says: “the same colonnade when seen from one end appears tapering, but from the middle symmetrical from each side” (PH 1, 118).³³⁸ I take it we are to imagine standing between a pair of parallel rows of columns. If we stand at one end of the rows, the columns will appear to be getting closer and closer together, in a single uniform sequence, as one runs one’s eye along the rows from one end to the other; but if we stand in the middle of the rows and face in either direction, they will appear to be getting closer together, albeit to a somewhat lesser degree than in the first case, in two different and symmetrical sequences approaching both ends. Now, if this is the right way to read the example, then it involves both distances and angles or directions; in the second scenario one end looks different from how it looked in the first scenario, because of a difference in the distance, but in addition the entire colonnade has a symmetrical look because of being looked at (in two parts) from two opposite directions as opposed to being looked at (as a whole) from just one direction. Sextus, however, concentrates on the second aspect, referring to the symmetry in one scenario versus the tapering in the other. So although there is a way in which a difference of distance does figure in the example, what he draws attention to is not this, but a difference in angle(s) or direction(s).

The question now is whether the word can be understood to capture this aspect of the example. And however one translates it, it is difficult to see how it can be understood in this way. In general, refers to the extent by which things stand apart from one another; this need not always be understood in spatial terms, and for this reason ‘interval’ may sometimes be preferable as a translation to ‘distance’ (as in the case of musical intervals, for example). But the word is not used indiscriminately of any kind of difference; there does need to be some kind of identifiable gap between the items separated by a διάστημα. And there just does not seem to be any such identifiable gap in the case of different angles or directions of viewing.

As noted a moment ago, although this example could be seen as, at least in part, one involving different distances or intervals, this is not the side of it that Sextus chooses to emphasize. And so, if I am right about the term διάστημα, it follows that this example is not in fact best situated under the heading of διαστήματα; it might better have gone under the heading of “places”. It also follows that it is Sextus, not Diogenes, who is being “slightly inaccurate”, since the relevant examples in Diogenes do exclusively involve differences of distance. And finally, it follows that there is no significant difference between the terms used by the two authors; even though can refer to intervals that are not physical distances, physical distances are the only thing that it could in fact refer to in this passage of Sextus. So while the evidence may favour this, rather than ἀποστάσεις, having been Aenesidemus’ own term, nothing in our interpretation of the passage turns on this.

Aside from the precise terminology, what kinds of cases are collected under these three headings? With the exception of the case just discussed, Sextus organizes the data in an orderly manner, beginning with examples where the same thing appears different from different distances – that is, closer up or further away – then continuing with examples where the same thing appears different in different places – such as in water as opposed to in the air, indoors as opposed to outdoors, or (of eggs) inside a bird as opposed to laid – and ending with examples where the same thing appears different in different positions – such as flat versus upright, or turned in one direction versus another. Diogenes begins by listing a number of general ways in which things may present differing and seemingly conflicting appearances – big versus small, square versus round, etc. – and then gives a number of specific examples. The last two of these examples also appear in Sextus, both as cases of different appearances in different positions: the picture that appears flat when laid horizontally, but three-dimensional when upright and viewed as an image, and the dove’s neck that appears differently coloured depending on which way it is turned. These are preceded in Diogenes by two cases of different appearances at different distances – mountains and the sun (though in the latter case, of course, we only have experience of the distant appearance)³³⁹ – and two of different appearances in different places – the sun at different points in the sky, and the same body in the woods or in open country. Contrary to Annas and Barnes, then, who regard Diogenes’ ordering as purely haphazard,³⁴⁰ this seems to follow the same order as Sextus once we get to the specific cases, even if these are preceded by generalities that follow no clear pattern. In addition, most of Diogenes’ general kinds of differences clearly recall, or at least clearly conform to, other examples in Sextus’ account. Diogenes’ big/small fits Sextus’ boat that appears small (and stationary) when at a distance, but larger (and in motion) when close up; Diogenes’ square/round recalls Sextus’ tower that looks round at a distance but square close up; Diogenes’ straight/bent recalls the oar that looks bent in water but straight outside it, one of Sextus’ examples under “places”; and Diogenes’ flat/with projections again recalls the picture, which, as just noted, appears later as one of Diogenes’ own specific cases.

It seems reasonable to infer, then, that although a number of the specific examples in Diogenes do not appear in Sextus, and also vice versa – Sextus’ colonnade does not appear in Diogenes, nor do several of Sextus’ examples under “places”, to which we will return – the original version of this Mode included a number of examples, sorted into groups according to each of the three main headings; and the examples most likely to have appeared in the original version are the ones that either occur directly in both Sextus and Diogenes or occur in Sextus and are suggested by Diogenes’ opening generalities.³⁴¹ The most likely of all is the oar that looks straight in the air but bent in the water, since this also appears in Philo’s version of this Mode. Aside from this, Philo’s version is mostly confined to generalities rather than specific cases;³⁴² but one of these general points is that polygonal objects sometimes look round, which is reminiscent of Sextus’ tower that looks square from close at hand but round from a distance.

At any rate, I think we have a fair idea of the flavour of the examples that Aenesidemus’ Mode will have included. The next question is how these examples are supposed to produce a sceptical result. For a natural reaction to the phenomenon of diverse and apparently conflicting appearances, on these subjects as on any others, is “so what?”. While conflicting appearances do at least present an issue, or a demand for explanation, there is no obvious reason why this should have sceptical consequences. As is well known, the oar that looks bent in water makes its first appearance in western philosophy in book 10 of Plato’s Republic. The point here is to illustrate that the part of the soul that includes the senses is liable to being deceived, and therefore less reliable than the rational part. This may of course lead us to mistrust the senses on certain occasions, but since the senses are only one part of our cognitive apparatus, it does not push us towards any kind of generalized scepticism. The effect is not to make us wonder about how things really are; on the contrary, the verdict that the senses are sometimes deceived relies on a confidence that we do have a grasp of this, from another source that does not share the senses’ limitations.

Again, Diogenes’ examples of the sun looking different when rising and at its zenith, and of mountains looking “airy” (ἀεροειδῆ) at a distance, but not when close up, are paralleled by examples in a treatise on optics from the third century BC, preserved in fragmentary form in a papyrus in the Louvre (PLouvre 7733). The numerous cases of conflicting appearances cited in this work actually persuaded one editor to regard it as a sceptical text.³⁴³ But this is a misconception; although the argument is extremely hard to make out in detail, the purpose of the treatise, at least in the part to which these surviving fragments belonged, was clearly to explain away various misleading appearances on the basis of an understanding of how certain optical phenomena come about. The author is not casting doubt on our ability to know how things are, but showing why things often look different from how they are, on the assumption that we know very well how that is.³⁴⁴ Philo’s approach, too, in this Mode as in others, is to present a number of cases of what he assumes to be deceptive appearances; he takes it that we have a grasp of how things really are, and concentrates on showing the ways in which we can be led astray. The oar is a good example; in Philo’s treatment this comes out as “Oars too, even if they are exceptionally straight, turn out to look bent under water”. We are not here being invited to question whether the oar is really straight or bent, but to ponder the fact that it sometimes does not look straight even though it really is. This is why I said that, though Philo makes use of the material in the Ten Modes, his purpose in doing so is not sceptical. Finally, the case of the square or round tower of course derives from the Epicureans, who claimed in radically anti-sceptical fashion that “all appearances are true”. As I understand this example (relying especially on Sextus, M 7, 208), what the Epicureans take to be true in this case is that the atomic images emanating from the tower and striking the sense-organs are indeed either round or square, depending on whether the tower is close or far away. If the tower is far away, the image, though starting out square – since it came from a square tower – has its corners worn off in transit, and so is in fact round by the time it reaches the viewer; but if the tower is close, the image does not have enough of a journey for this transformation to occur, and so it is still square when it confronts our senses. But whether or not this is the right way to read the example, the Epicureans were clearly not trying to subvert our grasp of how things really are, but to explain why things appear as they do by appeal to how they really are.

So what is it about the treatment of these examples in Sextus’ and Diogenes’ versions of this Mode that turns them in a sceptical direction? One point that sets these apart from the treatments of the same or similar examples mentioned in the previous paragraph is that all the appearances are considered on a par; there is no suggestion that some appearances are veridical and others not. This is obvious in Sextus, who scatters the word “appears” (φαίνεται) throughout this Mode, and who clearly and explicitly presents all the examples as cases of differing appearances – and no more than that. It is a little less obvious in Diogenes, because his examples are told in a more compressed form. But Diogenes starts his generalized examples by saying “things that seem large appear small” (τὰ δοκοῦντ᾽ εἶναι μεγάλα μικρὰ φαίνεται), and all the generalized examples then depend on this same δοκοῦντ᾽ and φαίνεται; the specific examples that follow then all depend on another single φαίνεται.

But this still does not get us to anything sceptical unless some move is made that is supposed to prevent us from ever getting beyond the level of mere appearances. In Diogenes this comes in a single closing sentence: “Since, then, it is not possible to perceive these things apart from places and positions, their nature is not known”. In Sextus’ version of the Mode a similar juxtaposition of points appears twice. Having rehearsed all his examples, Sextus immediately adds “Since, then, all the things that appear are observed in some place and from some interval and in some position – each of which creates a lot of variation for the appearance, as we have indicated – we will be compelled through this Mode, too, to come to suspension of judgement” (PH 1, 121). And then in concluding his treatment of this Mode he says: “[w]e are perhaps able to say how each thing appears in terms of this position or this interval or in this place, but we are not able, because of what was said before, to reveal what it is like in its nature” (123). The two versions seem, then, to agree on two things: first, we never observe things except in some place or in some position or at some interval, and second, because of this limitation, we are not in a position to determine the nature of these things.

How, more precisely, is this supposed to work? Diogenes says nothing more, as if it were immediately clear how one gets from the first point to the second. Sextus, on the other hand, inserts an argument between the two passages that I just quoted (121–123). He imagines that contrary to his own rigorous evenhandedness, someone tries to mount an argument to the effect that some of these appearances show us things as they really are, while others distort them. Against this, he argues that any such attempt would have to proceed with or without a demonstration (ἀπóδειξις). If there is no demonstration, then there is no reason why we should believe it. And if there is a demonstration, the veracity of that demonstration would itself be subject to demonstration, and so on. In other words, Sextus presents us with two of the Five Modes, those of hypothesis and infinite regress. Now the Five Modes, as noted earlier, are attributed by Sextus to an unnamed group of “later sceptics” – later, that is, than the purveyors of the Ten Modes. Hence this material cannot have appeared in the original version of the Mode in which we are interested; it must be a later importation by Sextus or his source. This kind of contamination of the Ten Modes by material from the Five Modes is not unusual in Sextus, but it never occurs in Diogenes’ presentation of the Ten Modes. Although Diogenes’ version of the Ten Modes is later than Sextus’ – as we saw, it refers to it, and may in certain respects be viewed as attempting to improve it 345– it is in this respect clearly more faithful to the Ten Modes as originally devised by Aenesidemus.

We are back, then, with the connection suggested by both Sextus and Diogenes: we are not able to get clear on the nature of things, and this is because we only ever encounter things at some interval or in some place or in some position. And we need to explain this connection without relying on the argument, indebted to the Five Modes, that we find in Sextus. Now one possibility, of course, is that even if it was left to the “later sceptics” to put the arguments collected under the Five Modes into a systematic form, arguments of this type could nonetheless have been used by earlier sceptics when it suited them; so the fact that Sextus introduces an argument that bears on its face the signs of having been lifted from the Five Modes does not mean that such arguments could not have figured in earlier versions of this Mode, perhaps in a more informal guise. As is well known, Aristotle confronts what are clear ancestors of several of the Five Modes in defending his own account of the structure of a science against challenges in Posterior Analytics (1, 3); the Five Modes, just as much as the Ten, are compilations of previously existing material rather than wholesale inventions.

But this would not address one striking feature of Diogenes’ and Sextus’ concluding remarks quoted earlier. In both authors our failure to grasp the nature of things is said, or at least implied, to be because of the fact that we only ever experience things in specific places or positions or at specific intervals. The Five Modes are designed to address any case where we are presented with conflicting appearances, and in that sense Sextus is not ill-advised to introduce material from those Modes; it seems to be suited to derive a sceptical result from the phenomena offered for our consideration. But the Five Modes have nothing specifically to do with the idea that our cognitive limitations are due to the fact that things are always in some place or position or at some interval; yet that seems to be something that both surviving versions of the Modes make a point to emphasize. And that suggests another way of understanding the argument, which may be closer to how Aenesidemus originally conceived it.

Annas and Barnes say “We find no unity in the Fifth Mode [i.e., in Sextus’ ordering], and it might properly be regarded as a set of three distinct modes”.346 Although they are right that the divisions of subject-matter in the Ten Modes are to some extent arbitrary, this seems to me an exaggeration. This Mode has to do with, in a broad sense, where the object is located; interval or distance, place, and position are distinct types of issue under this broad heading, but there is an obvious connection among them. Annas and Barnes also say that the examples themselves are “a mixed bag” – mixed, that is, in terms of their level of persuasiveness – and that some of them “do not seem to produce any conflict at all”. They point particularly to several examples in Sextus: eggs appear soft inside the bird and hard when laid, lyngurion (that is, lynx urine, which was supposed to congeal to form a kind of amber) appears liquid inside the lynx but hard in the outside air, and coral appears soft in the water but, again, hard in the outside air. And they say “It is absurd to wonder whether eggs are really hard or soft”, and similarly absurd, mutatis mutandis, for the other cases.³⁴⁷ But is this absurd? Or, to put it another way, should we assume that the examples were necessarily meant to produce conflict – which, as they rightly note, these do not appear to do? Trying to take these examples seriously may take us closer to understanding how the argument was supposed to work.

Recall that both Sextus and Diogenes seem to imply that our grasp of the nature of things is thwarted precisely by the fact that things are always in some place or position or at some interval from the viewer. Now this suggests that the nature of a thing would be the way the thing is independently of any place, position or interval (or any other particular circumstances, we might add – for this is just one Mode out of several). This nature would presumably be unaffected by the object’s particular place, position or interval from the viewer at any given time, and so would be invariant, at least as far as those features are concerned (but again, this Mode is not the only one). The fact that things strike us differently when they are in different places or positions or at different intervals makes it particularly obvious that we do not have access to this invariant nature; it also suggests that the way they strike us in these different conditions is due to the influence of those conditions themselves – which just reinforces the point about our lack of access, since the things are bound always to be in some condition or other.

Now, how does this apply to the bird’s eggs and related cases? The egg appears soft when inside the bird but hard after the bird has laid it. Obviously the egg is always in some place or other – either in the bird or outside it; and the character presented to us by the egg varies depending on which of these places it is in. But this means, according to the line of thought rehearsed in the previous paragraph, that it is not part of the egg’s nature to be either soft or hard. A thing’s nature does not vary with conditions, but the softness and hardness of the egg obtain only in certain specific conditions. Hence, if we are trying to make an inventory of the features that belong to the egg by nature, neither softness nor hardness will figure on that list – or at least, we will have no reason to think so. And if the same kind of variability with conditions can be shown to obtain with any of the observable features of the egg, this would seem to cut us off from any kind of grasp of its nature.

Notice that the notion that the appearances might be deceptive plays no necessary role in this line of thinking. It is not that we might be wrong in thinking that the egg is soft when inside the bird or hard when outside it. The point is simply that the egg’s softness is confined to its place inside the bird and its hardness to its place outside the bird; since these observed features are confined to one place as opposed to another, neither one of them can be taken to point towards the thing’s nature. And in this sense the question “Is the egg really hard or soft?”, which was regarded by Annas and Barnes as absurd, has a straightforward answer: “If by ‘really’ you mean ‘by nature’, we cannot say that it is really either hard or soft”. It might be wondered, in this case, why Sextus even speaks of the egg appearing soft in the one place and hard in the other; why not say that it is soft and hard respectively? The point, I take it, is to emphasize that the egg’s softness or hardness is not a guide to the nature of the thing, given each one’s restriction to a specific place. The egg presents itself as – and in this sense, “appears” – soft in one place and hard in the other, but neither “appearance” can be taken to show us how the egg is by nature. If this is the notion of appearance in operation here, it has a very respectable precedent. At the end of Republic 5 Plato has Socrates speak of the many beautiful things that will also appear ugly, the many just things that will also appear unjust, and so on (479a-b). Again the point is not that we might be mistaken in considering these things ugly in certain circumstances. On the contrary, the ugliness that they present in certain circumstances is taken seriously, as being a decisive obstacle to our considering them really beautiful; for something truly beautiful – something that we could legitimately say “is” beautiful – would have to manifest its beauty invariably and without regard to circumstances. Socrates’ point is that nothing in the sensible realm measures up to that standard – for the epithets “beautiful” and “ugly” or for any others; only the Forms do that. And that is his point in calling the beauty and ugliness of sensible things merely “apparent”.

Here, then, is a way of spelling out the contrast between the nature of a thing, and how it strikes us when in a certain place or in a certain position or at a certain interval, which does not depend on the kind of thinking characteristic of the Five Modes; the focus is not on a conflict between the thing’s appearances, but on the fact that these appearances are all restricted to certain specific conditions. Now, I have concentrated on a small cluster of examples, ones that seemed particularly inappropriate to an interpretation in terms of conflicting appearances between which one unsuccessfully attempts to choose. But most of the examples, in both Sextus’ and Diogenes’ versions of the Mode on which we have focused, are admittedly amenable to that interpretation, and it is no doubt most natural for us to read them in that way. However, it does not follow that they cannot also be read in the other way. Perhaps the oar can be considered to present a bent aspect when in water and a straight aspect when in the air, just as the egg presents a soft aspect when inside the bird and a hard aspect when outside it; perhaps the sun comes to assume different features as it occupies different positions in the sky; and perhaps doves’ necks change colour as they turn in different directions. If so, then in these cases, too, the restrictedness of each appearance to specific conditions would be the central notion, not the conflict between the two appearances and the pressure to try to choose between them.

It must also be admitted that the examples on which I have focused in developing this alternative interpretation – the egg, the coral and lyngurion – appear only in Sextus’ version of this Mode.348 By the standard that I introduced earlier, according to which examples that appeared both in Sextus and in Diogenes were more likely to go back to Aenesidemus than those that appear only in one author, these examples are clearly not ones that we can attribute to Aenesidemus with any confidence. However, the idea of a connection between the restrictedness of a thing’s appearances to specific conditions, and our inability to get at the nature of the thing, does appear in both authors, and it was that idea that I was using those examples to try to explain. One could well imagine that, if Aenesidemus did develop a line of thought of the sort that I have sketched, others might later have introduced examples that were especially suitable to that line of thought – perhaps more unambiguously so than the examples he himself had used.

I close with two final questions, both of which are independent of the question which of the two possible interpretations of this Mode that I have offered is closer to Aenesidemus’ original goal. First, does our examination of this Mode point to any particular conception of place or space on Aenesidemus’ part? The answer to this, I think, is clearly negative, and for this purpose it makes no difference which of the two interpretations one adopts. Either way, places, positions and intervals are simply a set of conditions of objects – one set out of many, as the multitude of Modes makes clear – that stand in the way of our grasping how those objects really are. For this purpose it does not matter what place itself is; the point is that being in different places, or in different positions, or at different intervals, results in the objects appearing differently, and that is the starting-point for sceptical reasoning. Nor, indeed, would we expect Aenesidemus, as a sceptic, to have advocated or presupposed any particular conception of place. We saw at the outset that Aenesidemus tackled topics in physics that are at least closely related to place, and that it would have been in no way surprising if, in the course of his scrutiny of physical doctrines, he did tackle place as a topic in its own right. But if so, we can assume that his approach was critical rather than constructive. Whatever his arguments on the subject may have been, they would in this respect have resembled the argument in the Mode on place and related matters. And in this respect Aenesidemus does not belong in the same company as most of the philosophers under consideration in this volume, who put forward conceptions and theories of place or space that deserve to be explained, analysed and assessed.

However, if Sextus’ approach to physics is any guide at all, we can also assume that Aenesidemus did engage in discussion about the conceptions and theories advanced by (in Sextus’ terminology) ‘dogmatists’ such as these. And this leads to my second question: is it possible to connect what Aenesidemus does in the Mode on place, etc. with his approach to physics in general? Not directly, perhaps. The Ten Modes mostly avoid theoretical contexts, working instead by the accumulation of everyday examples,³⁵¹ and the Mode on which we have focused is no exception. However, it is not hard to see that this Mode could quickly take one towards a much more fundamental debate between a sceptic and a proponent of some physical theory. As we saw, many of the phenomena appealed to in this Mode were also discussed by non-sceptical philosophers, and some of these claimed to have physical theories that would explain the appearances; rather than forcing us to suspend judgement about the way things really are, these philosophers would claim, the appearances made use of in this Mode can all be accounted for by a single consistent theory that accurately captures how things really are.

Suppose a scientist did challenge the effectiveness of this Mode along these lines. What might a sceptic say in response? There might be some objections that he could mount concerning the merits of the theory used to account for the appearances, and certainly Sextus’ work includes plenty of examples of this kind of argumentation. But he might also take the discussion to a deeper level, tackling the nature of scientific theory or practice itself. The Five Modes could be of assistance here, but there could also be considerations relating more specifically to the context of physics. And among the sorts of considerations that might be especially germane in this context would be those raised in Aenesidemus’ Eight Modes against the causalists, which, according to Photius, played an important role in Aenesidemus’ attack on the appeal to causes in physics generally (170b17– 22). Thus, even though the Mode on places, positions and intervals is not itself part of the Pyrrhonists’ detailed examination of physical theories, it could easily have served as the starting-point of a debate that went on to involve some of the most foundational questions in physics. At various points I have taken issue with Annas’ and Barnes’ reading of this Mode, but on this question I think they are absolutely right; as they say, the debate between the sceptic and the physicist that one can imagine being stimulated by this Mode “raises large questions in the philosophy of science which are still hotly debated”.352 And in this respect there is no reason to think that Aenesidemus’ original version of this Mode differed from the versions that we still possess. While there is a clear sense in which Aenesidemus was an ‘anti-physicist’, this does not at all mean that physicists could simply ignore him; and in an indirect way, at least, the Mode on which I have concentrated may have had a role in his ‘anti-physicist’ enterprise.353