The Cambridge Companion to Early Greek Philosophy

by A. A. Long

  Such an interpretation is available without forcing the texts. Sometimes (e.g., Herodotus VII.103.2; Plato Tht. 189d) matên is to be rendered not as “without purpose” but as “without reason” (“in vain” and “empty” have similar ranges of application). Given that construal of matên “from reason” is to be construed as “for a reason,” where the conception of reason is linked to that of rational explanation. The first part of the fragment (“Nothing happens at random, but everything from reason”) thus asserts, not universal purposiveness in nature, but a principle that we have already seen to be pervasive in atomism, the Principle of Sufficient Reason. Instead of a radical discontinuity between Leucippus and Democritus, the fragment, thus construed, attests commitment to a principle basic to atomism. The second half (“and by necessity”) makes a stronger claim, which links the notion of rational explanation to the notions of necessity and of cause. The stronger claim is that whatever happens has to happen, cannot but happen. This amounts to a specification of the reason whose existence is asserted in the first half of the sentence; nothing happens without a reason, and, in the case of everything that happens, the reason for which it happens is that it has to happen.12

  There are, therefore, no chance events, that is, no events which simply happen. On the other hand, we have evidence that the atomists assigned some role to chance in the causation of events, though precisely what role is not easy to determine. Aristotle (Phys. II.4 196a24-28), Simplicius (In phys. 327.24-26, 330.14-20), and Themistius (In phys. 49.13-16) all say that Democritus attributed the formation of every primal cosmic swirl13 to chance (indeed Aristotle finds a special absurdity in the theory that while events in a cosmos occur in regular causal sequences, the cosmos itself comes into being purely by chance). That might be thought to be confirmed by the statement in Diogenes Laertius’ summary of Democritus’ cosmology that he identified the cosmic swirl itself with necessity (IX.45). On this interpretation, the statement that everything happens by necessity is confined to events within a cosmos and states that all such events are determined by the atomic motions constituting the swirl. The swirl itself, however, is not determined by anything; it just happens. On this view necessity governs, but is local to, a world order, which itself arises by chance from a precosmic state where there is no necessity.

  The recognition of pure chance is, however, inconsistent with the Principle of Sufficient Reason, which we know the atomists accepted. A reconciliation is suggested by a passage of Aetius (I.29.7) “Democritus and the Stoics say that it [i.e., chance] is a cause which is unclear to human reason,” which may be read as asserting that the ascription of events to chance is a confession of ignorance of their causes, not a denial that they have causes. Some other pieces of evidence support this suggestion. Diogenes’ summary of the cosmology of Leucippus (IX.30-33) concludes with the sentence “Just like the coming into being of worlds, so do their growth, decay, and destruction occur according to a certain necessity, the nature of which he does not explain.” In line with his famous dictum, then, Leucippus held that all events, including the formation of worlds, happen according to necessity but was unable to say what it is that necessitates cosmic events. It is then plausible that either he himself or Democritus said that such events may be said to occur by chance, in the sense that we are (whether merely in fact or in principle is indeterminate) ignorant of their causes. Explanations of specific kinds of events and of particular events were governed by the principle that there are no chance events, but no attempt was made to offer explanations of the fundamental cosmic processes themselves. That need not imply that they are literally uncaused, but that they might as well be treated as such, since their actual causes are of a degree of complexity outstripping the powers of the human mind to discover.

  For the atomists, then, everything happens of necessity; the identification of necessity with the mechanical forces of impact and motion may have been due to Democritus. What exactly was his view on this? Aetius reports him as identifying necessity with “impact and motion and a blow of matter” (I.26.2). Are impact and motion given equal status in this identification, or is it taken for granted that motion is always caused by prior impact? On the former construal some motion may be either uncaused or attributable to a cause other than impact. In favour of the first alternative is Aristotle’s evidence (Phys. VIII.1 252a32-b2) that Democritus held that one should not ask for a cause of what is always the case. He might then have said that the atoms are simply always in motion. But while that principle allows him to exclude the question “What causes the atoms to be in motion?” the Principle of Sufficient Reason requires that the question “Why is any particular atom moving with any particular motion?” should have an answer, and it might appear inevitable that that answer should refer to a prior atomic collision, as is attested by various sources (e.g., Simplicius, Inphys. 42.10-11; Alexander, In metaph. 36.21-25).

  We have, however, to recall the evidence from Philoponus that atoms never actually collide or come into contact, with its implication that the basic physical forces are attraction and repulsion. On that view, most atomic motion is explained by the analogue of impact, namely repulsion, while the immobility of atoms relative to one another is explained by attraction, since the relative stability of atoms in an aggregate has to be explained, not by their literal interlocking but by their being held together as if interlocked by an attractive force operating over the tiny gaps between the atoms in the aggregate. But in addition, some form of attraction may also have explained some atomic motions; Sextus cites Democritus (M. VII.116-18) as holding that things of the same kind tend to congregate together, and as illustrating that by examples of the behaviour of animate (birds flocking together) and inanimate things (grains of different sorts being separated out by the action of a sieve, pebbles of different shapes being sorted together by the action of waves on a beach).

  That this principle was applied to the atoms appears from Diogenes’ account of the cosmogony of Leucippus where atoms of all shapes form a swirling mass from which they are then separated out “like to like.” The separation out of atoms of different sizes could adequately be accounted for by the stronger centripetal tendency of the larger, itself a function of their greater mass. But the context in Diogenes, where the atoms have just been described as being of all shapes, with no mention so far of size, suggests that “like to like” is here to be understood as “like to like in shape.” Aetius’ report of Democritus’ account of sound (IV.19.3) asserts that atoms of like shape congregate together, and it contains the same illustrative examples as the Sextus passage. It is plausible, though not explicitly asserted, that this same principle accounts for the formation of aggregates of spherical atoms, for example, flames.

  We have, then, some evidence that Democritus’ dynamics postulated three fundamental forces, a repulsive force that plays the role of impact in a conventional corpuscular theory and two kinds of attractive force, one that draws together atoms of the same shape and another that holds together atoms of different shapes in an atomic aggregate. It is plausible that he applied the term “necessity” to all three, regarding them alike as irresistible. It must, however, be acknowledged first that the evidence for this theory is extremely fragmentary and secondly that even if it is accepted we have no idea whether or how Democritus attempted to unify these forces into a unified theory. Stated thus baldly, the theory has obvious difficulties, for example, if two atoms of the same shape collide, do they rebound or stick together? If all atoms have both an attractive and a repulsive force, there must be some yet more basic principles determining what force or combination of forces determines their motion. Our sources give no hint of whether Democritus had so much as considered such questions.

  EPISTEMOLOGY

  While we have no evidence to suggest that Leucippus was concerned with epistemological questions, there is abundant evidence of their importance for Democritus. It is quite likely that the latter’s epistemological interests were stimulated at least in part by his
fellow-citizen and elder contemporary Protagoras (see pp. 302–4). Our evidence is highly problematic, in that it provides support for the attribution to Democritus of two diametrically opposed positions on the reliability of the senses. On the one hand, we have a number of passages, including some direct quotations, in which he appears to reject the senses as totally unreliable; on the other, a number of passages ascribe to him the doctrine that all appearances are true, which aligns him with Protagorean subjectivism, a position that he is reported as having explicitly rejected (Plutarch, Adv. Col. 1108f). The former interpretation is supported mainly by evidence from Sextus, and the latter mainly by evidence from Aristotle and his commentators, but we cannot resolve the question by simply setting aside one body of evidence in favour of the other, since (a) in the course of a few lines (Metaph. IV.5 1009b7-17) Aristotle reports both that Democritus says that either nothing is true, or it is unclear to us, and that he asserts that what appears in perception is necessarily true, and (b) Sextus (M. VII.136) ascribes some of Democritus’ condemnation of the senses to a work in which “he had undertaken to give the senses control over belief.” Prima facie, then, the evidence suggests that both interpretations reflect aspects of Democritus’ thought. Was that thought, then, totally inconsistent? Or can the appearance of systematic contradiction be eliminated or at least mitigated?

  The former interpretation is based on the atomists’ account of the secondary qualities, whose observer-dependence Democritus seems to have been the first philosopher to recognise. Our senses present the world to us as consisting of things characterised by colour, sound, taste, smell, and so forth, but in reality the world consists of atoms moving in the void, and neither atoms nor the void are characterised by any secondary quality. We thus have a dichotomy between how things seem to us and how they are in reality, expressed in the celebrated slogan (DK 68 B9): “By convention sweet and by convention bitter, by convention hot, by convention cold, by convention colour, but in reality atoms and the void.” Further, the distinction between the reality of things and the appearances which that reality presents has to be supplemented by an account of the causal processes via which we receive those appearances. Atomic aggregates affect us by emitting from their surfaces continuous streams of films of atoms which impinge on our sense organs, and the resulting perceptual states are a function of the interaction between those films and the atomic structure of the organs. For instance, for an object to be red is for it constantly to emit films of atoms of such a nature that, when those films collide with an appropriately situated perceiver, the object will look red to that perceiver.

  Hence we are doubly distanced from reality; not only phenomenologically, in that things appear differently from how they are, but also causally, in that we perceive atomic aggregates via the physical intervention of other aggregates (viz. the atomic films) and the action of those latter on our sense organs. A number of fragments stress the cognitive gulf that separates us from reality: (B6) “By this principle man must know that he is removed from reality”; (B8) “Yet it will be clear that to know how each thing is in reality is impossible”; (B10) “That in reality we do not know how each thing is or is not has been shown many times”; and (B117) “In reality we know nothing, for truth is in the depths.”

  This evidence immediately presents a major problem of interpretation. On the one hand, B9 and associated reports stress the gulf between appearance and reality, claiming that the senses are unreliable in that they misrepresent reality. That dogmatic claim presupposes that we have some form of access to reality, which enables us to find the sensory picture unfaithful to how things are in fact. On the other hand, B6, 8, 10, and 117 make the much more radical claim that reality is totally inaccessible, thereby undercutting the thesis that there is a gulf between appearance and reality. B7, “This argument too shows that in reality we know nothing about anything, but each person’s opinion is something which flows in,”14 and the second half of B9, “In fact we know nothing firm, but what changes according to the condition of our body and of the things that enter it and come up against it,” attempt uneasily to straddle the two positions, since they draw the radically sceptical conclusion from a premise about the mechanism of perception that presupposes access to the truth about that mechanism. We might conclude that Democritus simply failed to distinguish the dogmatic claim that the senses misrepresent reality from the sceptical claim that we can know nothing whatever about reality. An alternative strategy is to look for a way of interpreting the evidence that will tend to bring the two claims nearer to consonance with one another.

  We can bring the two claims closer to one another if the “sceptical” fragments are interpreted as referring, not to cognitive states generally but specifically to states of sensory cognition. These fragments will then simply reiterate the thesis that we know nothing about the nature of reality through the senses, a thesis that is consistent with the slogan stated in the first half of B9 and that dissolves the apparent tension internal to B7 and the second half of B9. Support for that suggestion comes from consideration of the context in which Sextus quotes B6-10, namely that of Democritus’ critique of the senses, of which Sextus observes: “In these passages he more or less abolishes every kind of apprehension, even if the senses are the only ones which he attacks specifically.” It thus appears that Sextus understands Democritus as referring in these fragments to the senses only, though in his (i.e., Sextus’) view the critique there directed against the senses in fact applies to all forms of apprehension. This is confirmed by the distinction that Sextus immediately attributes to Democritus between the “bastard” knowledge provided by the senses and the “genuine” knowledge provided by the intellect (B11). The latter is specifically said to be concerned with things that fall below the limits of sensory discrimination, and we must therefore suppose that the atomic theory itself is to be ascribed to this form of knowledge. This is supported by those passages (M. VIII.6-7, 56) in which Sextus associates the position of Democritus with that of Plato; both reject the senses as sources of knowledge and maintain that only intelligible things are real. For Plato, of course, the intelligible things are the Forms, whereas for Democritus they are the atoms, which are inaccessible to perception and, consequently, such that their properties are determinable only by theory.

  On this interpretation the position expressed in the fragments cited by Sextus is not general scepticism, but what we might term theoretical realism. The character of the physical world is neither revealed by perception nor inaccessible to us; it is revealed by a theory which, starting from perceptual data, explains those data as appearances generated by the interaction between a world of imperceptible physical atoms and sensory mechanisms also composed of atoms. But now, as Sextus points out (M. VIII.56) and Democritus himself recognised (in the famous “Complaint of the Senses” (B125)), scepticism threatens once again because the theory has to take perceptual data as its starting-point. As a result, if the senses are altogether unreliable, there are no reliable data on which to base the theory, so, as the senses say to the mind in B125, “Our overthrow is a fall for you.”

  Commentators who read B125 as expressing commitment to scepticism on the part of Democritus15 naturally reject the foregoing unitary interpretation. On this view B117 and B6-10 are not restricted to sensory cognition but express a full-blooded rejection of any form of knowledge, which must be seen as superseding the distinction between appearance and reality drawn in B9 (first part) and B11 and the claim to “genuine knowledge” in the latter. Yet Sextus presents B6-11 in a single context (M. VII.135-40) without any suggestion of a conflict within the collection. Moreover, in PH I.213-14 he points out that, though the sceptics resemble Democritus in appealing to phenomena of conflicting appearances, such as the honey that tastes sweet to the healthy and bitter to the sick, Democritus in fact uses those phenomena to support, not the sceptical position that it is impossible to tell how the honey is in fact, but the dogmatic position that the honey is itself neither sweet nor bit
ter. (I interpret the latter as the assertion that sweetness and bitterness are not intrinsic attributes of the structure of atoms which is the honey (see p. 190). Sextus, in short, sees Democritus not as a sceptic, but as a dogmatist. Indeed, Sextus does not cite B125, and it is possible that he did not know the text from which it comes; M. VIII.56 shows that he was aware of the problem that is dramatised in the fragment, but he clearly saw it as a difficulty for Democritus, rather than as signalling Democritus’ rejection of the basis of his own theory.

  At this point we should consider in what sense the theory of atomism takes the data of the senses as its starting point, and whether that role is in fact threatened by the appearance-reality gap insisted on in B9. According to Aristotle (GC I.2 315b6-15, I.6 325a24-26), the theory started from sensory data in the sense that its role was to save the appearances, that is, to explain all sensory data as appearances of an objective world. Both Aristotle and Philoponus (In GC 23.1-16) mention conflicting appearances as among the data to be saved; the theory has to explain both the honey’s tasting sweet to the healthy and its tasting bitter to the sick, and neither appearance has any pretensions to represent more faithfully than the other how things are in reality. All appearances make an equal contribution to the theory. That is a position which atomism shares with Protagoras, but the latter assures the equal status of appearances by abandoning objectivity; in the Protagorean world there is nothing more to reality than the totality of equipollent appearances. For Democritus, by contrast, the reconciliation of the equipollence of appearances with the objectivity of the physical world requires the gap between appearance and reality. Without the gap, a world of equipollent appearances is inconsistent, and hence not objective. But there is no ground for denying equipollence; qua appearance, every appearance is as good as every other. Hence the task of theory is to arrive at the best description of an objective world that will satisfy the requirement of showing how all the conflicting appearances come about.16