1It is a commonplace of Aristotelian biology that animals have the faculty of locomotion, i.e. they can move on their own – they do not need to be pushed or pulled. Nonetheless, many commentators believe Aristotle’s remarks about self-motion in Physics VIII amount in some way to a denial or severe qualification of the claim that animals move themselves, or are self-movers. And indeed, Aristotle does say that animals do not move themselves κυρίως (259b7). The main question I hope to resolve in this paper is what this means.

2Some sort of scholarly consensus about this matter has emerged. Nussbaum suggests: ‘Local motion is the only genuine self-motion; but even this is not strictly self-motion, since it depends on an external aition’1, and in an influential paper, Furley holds a similar but slightly more nuanced view: ‘An animal is correctly described as a self-mover, because when it moves, its soul moves its body, and the external cause of its motion (the ὀρεκτόν) is a cause of motion only because it is «seen» as such by a faculty of the soul. There must be an external object, however, and hence the movement of an animal does not provide an example of a totally autonomous beginning of motion’2.

3However, I wish to contend that Aristotle does not claim in Physics VIII that when an animal ‘self-moves’ the principle of its motion comes from its environment, and that a fortiori he cannot be arguing that what makes its self-motion ‘derivative’ or ‘improper’ is that the principle of that motion derives from outside the animal. The sense in which animals are self-movers is indeed not straightforward, but this is because a self-mover is divided into two – it consists of one part, A, which remains unmoving and another part, B, moved by A. So an animal is not straightforwardly or properly speaking something which moves itself, for it has one part (A) which is in fact not moved except accidentally. In this sense, the self-motion that the animal undergoes is not derived from the (whole) animal. But it is not that the environment is ultimately responsible for the animal’s self-motion – otherwise, as many commentators have pointed out, this would make a mockery of Aristotle’s frequently repeated claim that animal motion is due to the animal itself, or its soul.

4There are two texts relevant here, both from Physics VIII: 253a7-21 (from chapter 2) and 259b1-22 (from chapter 6). As Furley points out, these texts are in fact importantly related, and Aristotle even makes a remark at the end of the first passage which suggests the first is ‘an outline sketch, the detail of which is to be filled in by’ the second3.

Text 14

The third objection may be thought to present more difficulties than the others, namely, that which alleges that change arises in things in which it did not exist before, and adduces in proof the case of animate things: for an animal is first at rest and afterwards walks, not having been got to change by anything from without, as it seems. This, however, is false; for we observe that there is always some connatural part of the animal organism changing, and the cause of the change of this is not the animal itself, but, perhaps, its environment. Moreover, we say that the animal itself originates not all of its changes but [only] its locomotion. So it may well be the case – or rather perhaps it must be the case – that many changes are produced in the body by its environment, and some of these get the intellect or the appetite to change, and this again then gets the whole animal to change: this is what happens in sleep: though there is then no perceptive change in animals, nonetheless there is some change, and they wake up again. But we will leave this point also to be elucidated at a later stage in our discussion.

5The context is the following. In VIII 1, 251a8-b10, Aristotle has argued that for any given change, there must be a preceding one. For consider the thing, x, which changes. Either x came into being previously, or it didn’t. If it did, then x’s coming into being (a change) preceded the original change. But if x didn’t come into existence previously, and was just sitting there, as it were, waiting to change, then there must have been some change in the world to bring about the conditions to make x change5. However, the behaviour of animals seems to disprove the last part of this argument, as Aristotle points out in VIII 2. We observe that animals sometimes start moving even though nothing external has got them going: ἐγγίγνεται ἐν ἡµῖν ἐξ ἡµῶν αὐτῶν ἀρχὴ κινήσεως, κἄν µηθὲν ἔξωθεν κινήσῃ (252b19-21). But if nothing external has got them going, then it seems that no previous change is necessary. And so it seems that we can countenance the possibility that the universe was at rest, and then change was initiated by an animal without there needing to be any other preceding change. To take an example, we see the dog sitting – and then he gets up and walks outside. Nothing came and pushed him along; nothing came and pulled him up. He just got up and walked. As Aristotle states: ἡρεµοῦν γὰρ πρότερον µετὰ ταῦτα βαδίζει, κινήσαντος τῶν ἔξωθεν οὐδενός, ὡς δοκεῖ (253a9-11) – ‘for [an animal] is first at rest and afterwards walks, not having been got to change by anything from without, as it seems’.

6Well, this may be how things seem. But Aristotle immediately goes on to deny that this is how things are: τοῦτο δ’ ἐστὶ ψεῦδος (253a11). What is being denied is that ἡρεµοῦν… πρότερον µετὰ ταῦτα βαδίζει, κινήσαντος τῶν ἔξωθεν οὐδενός, i.e. that it walks after being at rest, although nothing external moved it. This is a complex statement, effectively a conjunction of three statements: (i) it walks; (ii) it was previously at rest; (iii) nothing external moved it. How many of these conjuncts does Aristotle think is false? Presumably (i) is not in doubt. But is it that (ii) is false, i.e. that (despite appearances) it was actually not at rest prior to getting up and walking? Or is it that (iii) is false, i.e. that (despite appearances) something external actually did move it? Or are both false?

7What follows in the text is a denial of (ii): ὀρῶµεν γὰρ ἀεί τι κινούµενον ἐν τῷ ζῴῳ τῶν συµϕύτων (253a11-12). The animal was not actually genuinely at rest; for there is always something6 changing or moving in an animal7. These changes are caused – perhaps8 – by the environment, and so do not qualify as self-movements, for there is only one way in which an animal can change which would qualify as a self-movement, and that is to change place, to engage in locomotion. (We can deduce, therefore, that those environment-caused changes will not be instances of locomotion of the animal.)

8Aristotle actually toys with the idea that it is necessary for there to be changes in the animal’s body due to the environment: this seems to be explained by his claim that some of these changes move the mind (τὴν διάνοιαν) or appetite (τὴν ὄρεξιν) which then go on to move the whole animal, for instance in sleep (περὶ τοὺς ὕπνους). The point is surely that when an animal sleeps, there are no perceptual changes in it (it doesn’t perceive anything), and yet nonetheless it will wake up again. And this is just as well, otherwise we would be doomed to eternal sleep. Thus, it is necessary for there to be changes in the animal’s body due to the environment – in order to ensure that animals wake up from sleep.

9So far, I perceive no threat to Aristotle’s theory that animals can indulge in self-motion. For a start, he has claimed that the only self-motion in which animals can indulge is locomotion, thus showing that he still thinks that animals can self-change. But the main point – i.e. the one relevant to the aim of the argument of Physics VIII – is that even when an animal self-changes, nonetheless there is always some change in the animal which precedes it, for there is always some part of the animal changing. The reference to what happens in sleep is to illustrate what kind of change Aristotle has in mind, and the example is used to justify (cf. γάρ, 253a19) the claim that there have to be such changes in an animal: even when the animal does not perceive something, it awakes from sleep thanks to certain changes going on in its body while it is asleep. There could be no more homely observation: we still wake up even if there is no alarm clock, no door slamming, or no-one shouting at us. And we wake up because (claims Aristotle) our digestive system has stimulated our thoughts and desires – presumably, thoughts about, or desires for, food9. Thus, self-movement can originate in an animal, but this does not threaten the thesis that there has always been change, for even when an animal self-moves, there was a previous change, because something is always changing in the animal.

Text 2

10The context of the next passage is rather more complicated. The thesis of Physics VIII 5 is that every series of moved things (a is moved by b, b is moved by c, c is moved by d, etc.) will eventually terminate with something which moves, although it itself is unmoved, i.e. an unmoved mover. The penultimate item in the series will be something which is said to move itself. This leads Aristotle to analyse in more detail what it is for something to move itself. He concludes that something which moves itself – a self-mover – must in fact be a complex body, consisting of one part A which is unmoved, and another part B which is moved by part A. ‘It is necessary, therefore, for the self-mover to have a part that causes motion while it is unmoved and a part that is moved but does not necessarily cause motion, with either both parts touching each other, or one part touching the other’ (258a18-21). Thus, to call something a self-mover is to say something which needs careful qualification. Indeed, Aristotle speaks as though it is only in a qualified sense that something counts as a self-mover: ‘It is clear, then, that the whole thing moves itself not insofar as a part of it is such as to move itself – rather, the whole thing moves itself, being moved and causing motion insofar as one part of it is the mover and another part the moved. For it is not the whole thing which causes motion, nor is it moved as a whole, but part A causes motion, while part B alone is moved’ (258a22-7).

11In chapter 6, Aristotle argues that for there to be continual motion in the universe, there must be one everlasting unmoved mover. He then considers once more whether the behaviour of animals poses a threat to this position. For maybe every chain of moved things terminates in a different self-mover, i.e. an animal. Perhaps the constant change in the universe is actually due to the many locomotive living beings in it: and perhaps their ability to move themselves and thereby move other things derives only from them, and we do not need to advert to a single unmoved mover for the whole universe. He argues as follows10:

Further it is evident from actual observation that there are things that have the characteristic of moving themselves, e.g. the animal kingdom and the whole class of living things, and this suggested the view that perhaps it may be possible for motion to come to be in a thing without having been in existence at all before, because we see this actually occurring in animals: they are unmoved at one time and then again they are in motion, as it seems. We must grasp the fact, therefore, that animals move themselves only with one kind of change, and that they do not move themselves with this kind of change strictly speaking, for the cause is not from the animal itself.
But there are other natural motions which take place in animals, and which they do not engage in through themselves, e.g. increase, decrease, and respiration: these are engaged in by every animal while it is at rest, that is, not in motion in respect of the motion it undergoes by its own agency; here the motion is caused by the environment and by many things that enter into the animal: such as, in some cases, nourishment – when it is being digested animals sleep, and when it is being distributed they awake and move themselves, the first principle being from outside. Therefore animals are not always in continuous motion by their own agency: something else is the thing that moves them, itself being in motion and changing as it comes into relation with each several thing that moves itself.
But in all these cases [i.e. cases of self-motion] the first mover – i.e. the cause of the animal’s being itself moved by itself – is nonetheless moved accidentally: that is to say, the body changes its place, so that that which is in the body changes its place also and moves itself by leverage.
Hence we may be sure that if a thing belongs to the class of unmoved things which move themselves accidentally, it is impossible that it should cause continuous motion.

12He begins with the familiar observation that animals move themselves, and raises the old worry that in them motion comes to be where before there was no motion. Then Aristotle makes a point which he considers of some importance (τοῦτο δὴ δεῖ λαβεῖν, 259b6): the relevant self-change in which animals can indulge is of one kind only – we know this to be locomotion from the previous passage – but they do not move themselves in this waystrictly speaking (οὐ κυρίως, 259b7). This seems to be explained immediately in the next few words: ‘for the cause is not from the animal itself’ (οὐ γὰρ ἐξ αὐτοῦ τὸ αἲτιον, 259b7-9).

13We have two main claims, then. (1) Animals self-move only with one kind of motion. (2) They do not move themselves in this way strictly speaking (because the cause is not from the animal itself). What follows comes in two parts, corresponding to these two claims. First, in lines 259b8-16, Aristotle makes observations about the other natural changes that an animal undergoes which are not self-motions (they are ‘experienced by every animal while it is at rest and not in motion in respect of the motion set up by its own agency’, 259b9-11)11. Then, in lines 259b16-20, he elaborates on the consequences of the fact that self-motion is not properly self-motion, and shows why this is important to the argument of the chapter as a whole.

14Let us look at lines 259b8-16 (the second paragraph of the text above) in detail. In them, Aristotle explicates the first claim, that animals do not move themselves in respect of every kind of change but only in respect of locomotion. He needs, therefore, to distinguish those changes in an animal which are due to the environment (and which are not therefore self-motions), from those which are not due to the environment. We are familiar with these environment-changes from chapter 2, but here we are told explicitly which changes they include: growth, diminution, respiration, digestion and distribution (259b9; 12-13). Aristotle once more attributes the operation of these changes to the environment (τὸ περιέχον, 259b11), this time adding as another causal factor ‘many of the things which enter into the animal’ (πολλὰ τῶν εἰσιόντων, 259b11-12), including ‘food’ (τροϕή, 259b12). And once again, Aristotle gives the example of the animal when it is asleep: it is the operation of these kinds of change within the animal which cause it to wake up, and once awake, it can go on to move itself (259b12-13). To underline the difference between self-motions and environment-changes, Aristotle points out that although animals are constantly changing through their interaction with the environment, they are not constantly self-moving. Hence, the principle of these other natural changes cannot be from the animal, but rather from the environment (259b13-16). Lines 259b8-16, therefore, serve to tell us which of the changes that an animal undergoes are the ones which Aristotle deems self-motions, and what the cause of these other changes is. They are not supposed to tell us any more – or so it seems to me – about how it is that self-motion is not properly so-called, or why that fact is so important to grasp. In fact, that is the task of the next part of the text (259b16-20).

15Before discussing lines 259b16-20, we need to investigate what Aristotle meant in the first place when he said that animals do not move themselves ‘strictly speaking’, because ‘the cause is not from the animal itself’. Now, an animal does not move itself strictly speaking, because one part of the animal moves another part of it. When something is true of an object in virtue of the fact that some part of the object has a certain property, it is entirely standard Aristotelian doctrine to claim that that which is true of the object is not true of it strictly speaking. Aristotle uses a wide range of locutions for this, e.g. κυρίως, πρώτως, ἀπλῶς, etc.12 So for instance, if we were to call a lecture long, this is not strictly speaking true: it is the length of time for which the lecture lasts which is long (Categories 6, 5b2-3: cf. κυρίως, 5a38). Similarly, we might call Socrates pale, but strictly speaking his surface is pale (Physics IV 3, 210a34-b1; cf. πρώτως, 210a33-4).

16As a parallel to the thought that a self-mover does not self-move properly speaking, consider the following example from Physics IV 3, 210a25-b21: a jug of wine is in itself, but not strictly speaking (here, πρώτως)13. Neither part (the jug nor the wine) is said to be in itself, but the whole (the jug of wine) is (λεχθήσεται τὸ ο ὅλον ἐν αὐτῷ, 210a28-9), because one part (the wine) is in another (the jug). This sounds strange, but is simply a case where we would more naturally talk of ‘self-containment’. Here, the fact that one part of a complex whole bears a relation R to another, means that the whole in a sense bears R to itself. Similarly, in Physics VIII 6, or so I contend, an animal in a sense moves itself, because one part moves another. I believe that this is what Aristotle was trying to explain when he states that the cause of the self-movement of an animal is not ‘from the animal itself’ (οὐ γὰρ ἐξ αὐτοῦ τὸ αἴτιον, 259b7-9). The remark is entirely apposite, for the cause of an animal’s motion is not from the animal itself, it is from a part of the animal14. The contrast is not now between the cause of the animal’s motion being external to it and being internal to it; the contrast is now between the cause of the animal’s motion being from it and being from part of it.

17I paraphrase the argument of the text so far as follows: Animals self-move with only one kind of motion, i.e. locomotion (259b6-7), and they do not move themselves with this kind of motion properly speaking, because the cause is not from the animal itself, but rather from a part of it (259b7-8). There are of course other natural changes an animal undergoes which are not self-motions and which it undergoes continually, even when not moving itself, e.g. growth, decay, digestion, etc. (259b8-11). These changes are brought about by the environment and things ingested by the animal; they regulate sleep and waking (the animal can in fact self-move when awake) – they are going on continually and hence their principle must be external to the animal, since the animal does not move itself continually (259b11-16).

18Remember that Aristotle had stated that it is ‘important to grasp’ that animals do not move themselves strictly speaking (τοῦτο δὴ δεῖ λαβεῖν, 259b6); we still do not know why this is so important. But in the following part of the text, 259b16-20, this becomes clear. When an animal self-moves, there is an unmoved part which moves the rest of the animal – this much we know from the fact that an animal does not move itself properly speaking, since one part moves another. But in that case, the unmoved part (which moves the other part) ends up moving accidentally (κατὰ συµβεβηκός, 259b18) along with the organism as a whole. However, it is just this which is the crucial point for Aristotle’s argument, and which defuses the threat posed by animals to his argument of Physics VIII 6. For Aristotle goes on to claim: ‘we may be sure that if a thing belongs to the class of unmoved things which move themselves accidentally, it is impossible that it should cause continuous motion’ (259b20-2). Therefore the souls of the self-movers which Aristotle is considering – viz. animals – cannot be the unmoved movers responsible for the continual motion of the universe. No wonder he thought that it was so important to grasp that animals do not move themselves strictly speaking because one part moves another – it is precisely this fact which means that his argument in Physics VIII can proceed according to plan. The self-motion of animals is not properly speaking self-motion, because one part of the animal moves another, and this means that the unmoved movers within the animals – their souls – are actually moved accidentally, thus ruling them out as causes of the continual motion of the universe.

The orthodox interpretation

19Some commentators have thought that when Aristotle says that the cause of an animal’s self-motion is not from the animal itself, he means to claim that the cause is from outside the animal, i.e. from the environment. The problems with this interpretation are obvious. It makes a nonsense of the idea that an animal self-moves. It is also quite obviously flatly contradicted by remarks made in our passage itself, for in it Aristotle distinguishes self-motion from changes due to the environment (they are the ones which the animal undergoes even when it is not self-moving). Moreover, he goes on to talk of ‘the first mover’ and ‘the cause of the animal’s being itself moved by itself’ (τὸ κινοῦν πρῶτον καὶ τὸ αἴτιον τοῦ αὐτὸ ἑαυτὸ κινεῖν, 259b17) as being in the animals, and hence moved accidentally when the animal moves: clearly, Aristotle is talking here of the soul of the animal as being the first mover of the self-motion of the animal, just as you would expect.

20At least three things have led commentators to interpret the text in this rather unhappy way. (i) They assume that ‘the cause is not from the animal itself’ (οὐ γὰρ ἐξ αὐτοῦ τὸ αἴτιον, 259b7-9) must mean that the cause is external to the animal, and that this is why the self-motion of an animal is not self-motion strictly speaking. (ii) They assume that when Aristotle says ‘when [food] is being digested animals sleep, and when it is being distributed they awake and move themselves, the first principle being thus originally derived from outside’ (259b12-14), the phrase ‘the first principle being thus originally derived from outside’ refers to the first principle of the self-movement rather than their waking (both of which events are mentioned in the preceding phrase). (iii) They look to the De Motu Animalium, in which Aristotle is happy to say things like this: κινεῖ πρῶτον τὸ ὀρεκτὸν καὶ διανοητόν (‘the object of desire and also of thought primarily moves [the animal]’, 700b24), and happy to call the objects of pursuit and avoidance the ἀρχὴ… τῆς κινήσεως (701b33).

21(i) I have already said what I take οὐ γὰρ ἐξ αὐτοῦ τὸ αἴτιον to mean, and so I hope that it is clear that there is at least an alternative translation of these words to the translation favoured by those who propose the orthodox interpretation. The punctuation of the OCT text does initially tempt to one to think that lines 259b8-16 are intended to say more about why the cause of self-motion is not from the animal, and since those lines deal with changes whose cause is external to the animal, commentators have assumed that this is what Aristotle meant by οὐ γὰρ ἐξ αὐτοῦ τὸ αἴτιον. But in those lines Aristotle is trying to contrast externally-caused changes with self-motion, not conflate them.

22(ii) If what Aristotle says in Physics VIII 6 is to be consistent with what he said in chapter 2, then in 259b12-14, the principle which is external must be the principle of the animal’s waking. For we know from the passage in Physics VIII 2 discussed above that it is changes the animal undergoes when it is asleep which induce change in the διάνοια or ὄρεξις of the animal, i.e. what wakes the animal. Our passage in Physics VIII 6 expands on this: πεττοµένης µὲν γὰρ καθεύδουσιν, διακρινοµένης δ’ ἐγείρονται καὶ κινοῦσιν ἐαυτούς, τῆς πρώτης ἀρχῆς ἔξωθεν οὔσης (259b12-14). Both sleeping and waking are attributed to changes involving food, and not self-motions: but once the animal is awake, it goes on to move itself. It should certainly be a non-starter to think that Aristotle here means that the first principle of the animal’s self-movement is from outside, for familiar reasons: he goes on just a few lines later to identify ‘the first mover’ and ‘the cause of the animal’ s being itself moved by itself’ as something within the animal itself, i.e. its soul.

23Clearly, point (iii) poses an interesting problem of interpretation. If Aristotle is happy in the De Motu Animalium to call food etc. a principle of animal motion and say that food etc. moves the animal, then surely he might be saying just this in Physics VIII 2 and 6? Well, in the De Motu Animalium, Aristotle expands his investigation into animal motion to include an account of the role of the objects of thought and desire, and he underlines the importance that they play in a full account of animal motion. But he carefully qualifies the sense in which the objects of thought and desire move the animal: ᾗ γὰρ ἕνεκα τούτου ἄλλο, καὶ ᾗ τέλος ἐστὶ τῶν ἄλλου τινὸς ἕνεκα ὄντων, ταύτῃ κινεῖ (‘For insofar as something else is done for the sake of this, and insofar as it is an end of things that are for the sake of something else, thus far it moves’, 700b26-8), and significantly, he never goes on to draw the conclusion that an animal is not strictly speaking a self-mover. In fact, he is still quite happy to continue saying that the soul moves the animal (e.g. 700b10). The objects of thought and desire are brought in as necessary additions to the account of animal self-motion, not as items which challenge whether an animal genuinely moves itself.

24Conversely, the changes that Aristotle attributes in Physics VIII 2 and 6 to the interaction between the animal and the environment (digestion, respiration, growth etc.) are contrasted there with what goes on in standard cases of animal locomotion – rightly, since there is a big difference between, say, my waking up (which happens as a result of natural processes of digestion etc. regulated by environmental conditions) and my moving towards the glass of water on the table (which happens because I am thirsty and see the glass of water there).

25Aristotle is simply not interested in Physics VIII 2 and 6 in the further role that the objects of desire and thought play in the account of animal motion: all that matters for the argument there is that the soul is responsible for those motions (and that is why they count as animal self-motions). To see why he is not interested in that role, take Aristotle’s claim in Physics VIII 2 that prior to every change there is another change. The truth of this claim seems to be threatened by the following scenario: there I am, lying in bed, and suddenly I get up and fetch the water. Suppose Aristotle then points out that I desired water and saw the glass of water (i.e. he brings in the object of desire as playing some role in a full account of my self-motion): it is still the case that I have moved having previously been at rest! The role the glass of water plays in the causal story is of no help in defusing that problem – one cannot appeal to some prior change the glass of water has undergone, or something like that, since the only plausible change that takes place is in me, and that is what demands an explanation! Similarly, if we think of the problem of Physics VIII 6, namely whether animal souls are responsible for the undying change of the universe, again the role of an external object of thought or desire will be of no interest or help. For Aristotle’s argument against this possibility is that an animal soul moves coincidentally when an animal moves itself – this fact is utterly independent of the role of the object of desire.

26Thus, I do not think that there is any need to interpret the texts in Physics VIII in the orthodox way. There is another, better, way – the way I have suggested. It is true that there is one remark which could mislead – and indeed has misled – readers, namely the remark that animals do not move themselves locally strictly speaking, because the cause is not from the animal itself. I have proposed an interpretation of this remark which avoids the obvious and difficult problems that the orthodox interpretation raises.

A final puzzle

27The important thing left to understand is quite why Aristotle thinks that ‘if a thing belongs to the class of unmoved things which move themselves accidentally, it is impossible that it should cause continuous motion.’ The explanation – such as it is – comes in the ensuing paragraph15:

So the necessity that there should be motion continuously requires that there should be a first mover that is unmoved even accidentally, if, as we have said, there is to be in the world of things an unceasing and undying motion, and the world is to remain self-contained and within the same limits; for if the principle is permanent, the universe must also be permanent, since it is continuous with the principle. We must distinguish, however, between accidental motion of a thing by itself and such motion by something else, the former being confined to perishable things, whereas the latter belongs also to certain principles of heavenly bodies, of all those, that is to say, that experience more than one locomotion.

28No-one can pretend that this part of the argument is easy. Why should the fact that an animal soul moves itself accidentally prevent it from being the cause of undying motion? Understanding this is the principle difficulty of interpretation at this point in Aristotle’s Physics. The remarks in Physics VIII which commentators have thought pose problems for Aristotle’s theory do not in fact: as a result, our attention has been diverted from the main points of interest in the long and complex argument of Physics VIII16.