5.1 An Inconsistent Triad of Tenets?

In the De Anima, Aristotle seems emphatically to endorse three tenets concerning the role of the perceptive soul that prima facie appear to be mutually incompatible.

The soul is ‘the principle (ἀρχή) of living beings’ (An. 1.1, 402a6–7), and because living beings are distinguished from the non-living primarily by moving in characteristic ways and by knowing the world around them, the soul is to be understood, primarily, as the principle of these two activities (An. 1.2, 403b24–8). They can, and should, be further subdivided: first, into ‘motion with respect to nutrition, diminution, and growth’ (also characteristic of plants) on the one hand, and locomotion (specific to animals) on the other; and, second, into perception (characteristic of all animals) on the one hand and thinking (specific to rational animals) on the other.Footnote ¹ The soul is then to be studied as ‘the principle of the [four] enumerated phenomena’ (An. 2.2, 413b11–12), for – to repeat once more – the ‘soul is the cause and the principle of the living body’ (An. 2.4, 415b7–8). This is the basic framework within which Aristotle’s inquiry into perception is set, as Aristotle reminds us in its closing sentence: ‘Concerning the principle on account of which the animal is said to be capable of perception (αἰσθητικόν), let it be determined in this way’ (An. 3.2, 427a15–16). Hence, according to Aristotle:

• [Causality of Soul_P] The perceptive soul is the first principle of perceiving: it is primarily on account of having perceptive soul that animals, unlike non-living natural bodies and plants, can engage in perception.

It is more difficult to say how exactly this claim should be developed – that is, to spell out what difference exactly the soul’s presence makes and in what way. The difficulty of this question is underlined by Aristotle’s distinction (at An. 2.4, 415a8–28) between three senses in which the soul is the cause of life to the ensouled body.Footnote ²

It is by pondering these questions that one can arrive at what appears to be a tension between two other tenets that Aristotle endorses in the De Anima. We are by now sufficiently familiar with the first of these:

• [Passivity of Perception] Perceiving is a kind of being affected by and assimilated to perceptual objects.

We have seen that Aristotle has ascribed a crude version of this claim to most of his predecessorsFootnote ³ and that he explains how it is to be correctly understood in An. 2.5. It is a claim that is repeatedly reaffirmed throughout his inquiry into perception in An. 2.6–3.2 and – building on its results – within his inquiry into thinking in An. 3.4–8.Footnote ⁴ We are also familiar with at least two strategies for deflating this tenet, either by interpreting the preservative πάσχειν in An. 2.5 as referring to any transition from a second capacity to its fulfilment (Deflationary Interpretation), or by understanding the perceptual affection and assimilation as only a necessary condition or the material component of perception (Material Interpretation). Furthermore, we are also acquainted with the strategy of reading An. 2.5 as delimiting exactly the sense in which the perceptive soul itself can be affected by perceptual objects (Psychic Interpretation). We shall now see how these strategies of reading An. 2.5 underlie different approaches to Aristotle’s causal account of perception.

Let us begin from observing that the two tenets introduced thus far – the Causality of Soul_P and the Passivity of Perception – combine very naturally into the idea that

• [Platonic Formula] Perception is a ‘change of the soul [occurring] through the body’ (κίνησις διὰ τοῦ σώματος τῆς ψυχῆς).

The formulation comes from Somn. 1, 454a7 and is echoed at Phys. 7.3, 248a6–9.Footnote ⁵ I call it the Platonic Formula because it seems to draw directly on how Plato describes perception in several of his dialogues:

By accepting this formula, one becomes committed to the claim that:

• [Passivity of Soul_P] The perceptive soul is passive: it is itself the subject of the change (κίνησις) caused by perceptual objects.

There is, to be sure, nothing obviously wrong with or inconsistent about the Platonic Formula or the Passivity of Soul_P themselves. The difficulties arise from the fact that in An. 1.3–4 Aristotle introduces a battery of arguments against both. He argues that the soul in general cannot be the proper subject of any change, and so that:

• [Impassivity of Soul_P] The perceptive soul is impassive.

This tenet appears to constitute an inconsistent triad in conjunction with the Causality of Soul_P and the Passivity of Perception. This is so at least as long as we are committed to the following claim:

• [Cause/Subject] The soul can only be the primary cause of φ-ing by being the proper subject of ψ-ing in which φ-ing consists.

Cause/Subject makes the following implication valid: if perception consists in being affected (Passivity of Perception) and the perceptive soul is the primary cause of perceiving (Causality of Soul_P), then the perceptive soul must itself be affected (Passivity of Soul_P).

If this implication is in fact valid, then it transpires that there are no more than two ways of dealing with the apparent inconsistency.Footnote ⁷ One can either deny the Passivity of Perception or affirm the Passivity of Soul at least in the case of perception. In other words, one can either infer by modus tollens that, despite what Aristotle seems to be affirming throughout An. 2.5–3.8, perception cannot be passive, or one can infer by modus ponens that, despite what Aristotle seems to be arguing for in An. 1.3–4, the perceptive soul cannot be impassive. The third possibility would be to reject Cause/Subject, and so the validity of the implication based on it, and to insist that the whole triad of the Causality of Soul_P, the Passivity of Perception, and the Impassivity of Soul_P can, in fact, be endorsed in a consistent way. But one would have to explain how this is to be achieved.

This analysis is admittedly very abstract and preliminary, and much depends on how exactly each of the three tenets is spelled out. If, for instance, one understands the Passivity of Perception, along with the Material Interpretation, as concerning only a necessary condition or the material constituent of perception, then there will not seem to be any inconsistency to address. This interpretative manoeuvre, however, is far from innocent, for Aristotle’s repeated claim that perception is a kind of being affected seems to say something more than what Material Interpretation is ready to take on board. Indeed, if the argument of the preceding chapters is on the right track, it provides strong reasons for resisting this move.

One can also object that there is no need to choose among the three options sketched out above: one’s interpretation can surely combine them in various ways. I do not want to deny that. However, the truth is that most existing interpretations can be characterized as leaning either towards qualifying/denying the Passivity of Perception or towards endorsing a certain Passivity of Soul_P. I hope to show that the abstract scheme introduced above is helpful insofar as it provides a basic orientation about the main directions in which one can go in seeking to resolve what emerges as a key difficulty of Aristotle’s account.

In the remainder of this chapter, I shall explore this difficulty and the three possible ways of resolving it in more detail. I begin by saying more on how the claim that the soul cannot be the subject of any motion or change (underlying the Impassivity of Soul_P) is developed in An. 1.3–4 and why the strategy consisting in rejecting Cause/Subject is attractive but difficult (Section 5.2). I then discuss the remaining two strategies as developed by the first ancient proponents known to us, focusing on the difficulties encountered by their interpretations (Sections 5.3 and 5.4). It will turn out that the scheme outlined above captures the structure of an actual historical disagreement between Alexander of Aphrodisias and Themistius that continues to dominate the discussion even today. In Section 5.5, I briefly reflect on an unorthodox medieval interpretative tradition that may help us identify the ground on which Cause/Subject can meaningfully be rejected even in the case of perception.

5.2 The Impassivity of the Perceptive Soul

At the outset of An. 1.3, Aristotle promises to show that not only is the view according to which the soul is self-moved (endorsed by Platonists and Aristotle’s other predecessors) false, but, more generally, that the very idea of ‘a change (κίνησις) belonging to it [i.e. the soul] is utterly impossible’ (406a2–3). He then goes on to develop an intricate argument throughout An. 1.3–4 against any attempt at ascribing change (κίνησις) to the soul itself. He begins with a battery of general arguments against the idea of the soul undergoing a change (1.3, 406a12–b15) before then objecting in more detail to Democritus’ and Plato’s versions of that idea (1.3, 406b15–407b12).Footnote ⁸ Next, in a kind of digression, he formulates a more general objection against Plato’s account ‘and, indeed, most of existing accounts of the soul’ that do not pay sufficient attention to the kind of ‘community’ that each kind of soul must have with the specific kind of body that it ensouls, likening the soul, for the first time, to art (1.3, 407b12–27). Then, as a sort of antithesis to this negligence (typical for the idea of a transmigratory soul), Aristotle discusses the notion of the soul as a harmony of the body (1.4, 407b27–408a19).Footnote ⁹ Only then does he return to the leading question of whether the soul can be the subject of a change (1.4, 408a29–34) and he continues addressing it in a pair of dense and difficult passages (1.4, 408a34–b18, 408b18–30), the first of which will be the focus of our discussion below. The entire argument is then finally closed at An. 1.4, 408b31–2 when Aristotle reaffirms that (a) ‘the soul cannot undergo any change whatsoever’, and that, therefore, (b) it also cannot move itself in any other way than coincidentally – that is, by being in the body that it moves.Footnote ¹⁰

It is interesting for our question that perception plays a discreet but pivotal role in this intricate argument, despite the fact that the official discussion of it has been reserved for An. 1.5.Footnote ¹¹ This is because perception is singled out as the best candidate for a change (κίνησις) belonging to the soul itself: ‘One would most reasonably assume that the soul undergoes a change (κινεῖσθαι) by the agency of (ὑπό) perceptual objects, if it can undergo a change at all’ (An. 1.3, 406b10–11).Footnote ¹² Aristotle returns to this observation at the outset of the so-called Rylean passage (An. 1.4, 408a34–b18),Footnote ¹³ where perception (together with passions and, a bit surprisingly, discursive thinking) is introduced again as a phenomenon in whose case it would be more reasonable than in the case of locomotion to assume that the soul is itself undergoing a change. But Aristotle argues that this need not be the case. Although the passage is firmly set in the context of An. 1.3–4 and Aristotle’s argument is mostly a negative endeavour aimed at showing that a conclusion widely endorsed by his predecessors is not necessary, it turns out to be important for understanding his own overall strategy. Indeed, different approaches to this passage are intimately connected to different ways of resolving the dilemma outlined in the preceding section. Hence, it will be worth discussing the text in some detail.

After summarizing the established claim that the soul can be moved in place only coincidentally insofar as the body – in which it is – is moved in place (An. 1.4, 408b29–34), Aristotle formulates and addresses the following difficulty:

The inference, which is here applied to (a) passions, (b) perception, and (c) discursive thinking, closely resembles the above-mentioned implication based on Cause/Subject. The main difference is that instead of the Causality of Soul, we find here another premise based on how we talk about the soul: ‘we say that the soul φ-es’. The rest is identical: assuming that φ-ing is a kind of undergoing a change, it seems to follow that the soul itself undergoes a change – contrary to Aristotle’s earlier argument (1.3, 406a12–b15). Now, why should we ascribe any importance to how we talk about the soul? What makes this kind of talk (‘the soul φ-es’) at least remotely plausible for Aristotle is apparently nothing other than the Causality of Soul. If this is endorsed in conjunction with Cause/Subject, as Aristotle takes his predecessors to have widely done, then the conclusion (implying the Passivity of Soul) seems, indeed, unavoidable.Footnote ¹⁴ This background becomes important for understanding how the argument unfolds.

In the first step, Aristotle begins to explain why the conclusion is, in fact, not necessary at least for (a) passions and (c) discursive thinking:Footnote ¹⁵

We can leave aside for now the complications relating to the case of discursive thinking (διανοεῖσθαι) and focus instead on Aristotle’s argument concerning passions. We are invited to grant (at least for the sake of argument) that (i) each of them is a kind of ‘undergoing a change’ (κινεῖσθαι), apparently (iv) a kind of being altered, and that (ii) the soul is directly involved in them, namely as their primary efficient cause. Having done so, we should realize that this does not produce the conclusion that the soul undergoes a change, because (v) saying that the soul is angry and the like comes much to the same result as if one were to say that the soul itself weaves or builds.

Along with most interpreters, I believe that the idea of the soul weaving or building in (v) is intended to sound absurd.Footnote ¹⁷ However, unlike many readers, I do not think that Aristotle’s point is that we should evade the puzzle from 408a34–b5 by simply rejecting the first premise (‘the soul φ-es’). Rather, I take the thrust of the argument to be that the first premise requires reformulation in an appropriate way along the lines of the Causality of Soul, as Aristotle suggests in what immediately follows (see (vi) quoted below). This does not constitute on its own a solution to the puzzle, but it is an important step forward, at least for phenomena (a) and (c). Put very roughly, it allows Aristotle to accept the Causality of Soul without thereby committing himself to Cause/Subject. Once the first premise of the initial puzzle from 408a34–b5 is reformulated in this way, it can be spelled out – as an alternative to Cause/Subject – in terms of the soul being the efficient cause of the phenomena in question along the lines of (ii). In this way, Aristotle effectively subsumes the causal role of the soul in these phenomena under the model of unmoved movers (to which he already referred at An. 1.3, 406a3–4 as something taken for granted): we can accept that (i) φ-ing consists in being changed, and that (ii) the soul is the primary cause of it, without endorsing the conclusion that the soul itself is being changed; rather, it is an unmoved mover of the phenomena in question.

Indeed, as we shall see, this is exactly what Aristotle is suggesting in the remainder of the passage (408b13–18). However, there is more going on here. Thus far, (b) perception has been left aside, and for good reason, because it seems implausible to describe it as a change caused by the soul (i.e. a case of κινεῖσθαι ὑπὸ τῆς ψυχῆς). Rather, it clearly appears to be a change caused, first and foremost, by the perceptual object. So, the role of the soul in perception cannot be subsumed under the model of unmoved movers in any straightforward way; in this sense, the passage confirms what has already been claimed at An. 1.3, 406b10–11: ‘One would most reasonably assume that the soul undergoes a change by the agency of perceptual objects [i.e. in perceiving], if it can undergo a change at all.’ But in the closing lines of the present passage, Aristotle returns to perception and insists that, in whatever way the role of the soul is to be exactly spelled out, we should resist, even in this case, the conclusion pressed on us by Cause/Subject – apparently because it is wrong even in the case of perception. Aristotle begins from a suggestion for reformulating the first premise of the puzzle from 408a34–b5:

Aristotle’s claim in (vi) was influentially interpreted as denying – in a Rylean spirit – that the soul can be the subject of any φ-ing whatsoever.Footnote ¹⁹ But I take this idea to have been successfully disproven. What Aristotle says is only that no phenomenon that can be defined as, or is in part constituted by, undergoing a change can be ascribed to the soul itself.Footnote ²⁰ However, this category of phenomena clearly does not exhaust all possible kinds of φ-ing: even if we leave thinking (νοεῖν) aside, which, according to Aristotle, is emphatically not a change or motion,Footnote ²¹ his theory of agency allows one to insist, comfortably, that X φ-es without implying that X is the subject of a change.Footnote ²² In the case of locomotion or passion, for instance, ‘on account of the soul’ will be spelled out as ‘by the agency of the soul’ – that is, ‘on account of the soul moving the body’. Here, the way in which the soul is the primary cause of φ-ing is understood in terms of the soul being the proper subject of ψ-ing, which, however, is not a case of undergoing a change. Thus, Aristotle does not reject – but rather presupposes – the idea of the soul as a subject.

I do not mean to suggest that this idea is clearly formulated here or easy to tease out.Footnote ²³ But the notion of the soul as an unmoved mover of the body is not new in our passage. In fact, Aristotle introduced it at the very outset of his discussion in An. 1.3–4 as an alternative to Cause/Subject when applied to locomotion. Here, he presented the notion as something that has already been established elsewhere:Footnote ²⁴ ‘that it is not necessary for that which moves [i.e. the soul as the primary cause of animal self-motion] to be itself undergoing a change has been said before’ (An. 1.3, 406a3–4).Footnote ²⁵ So, once the role of the soul in phenomena (a) and (c) is subsumed under the model of unmoved movers in (ii), Aristotle’s preliminary work is basically done.Footnote ²⁶ What is novel and, indeed, unique about our passage – in the context of An. 1.3–4 and beyond – is Aristotle’s suggestion in (vii) that the same kind of analysis should be extended, mutatis mutandis, to perception – although we know that this is the most difficult case.Footnote ²⁷ One reason why it is difficult is that, in this case, Aristotle cannot simply refer to any model already developed elsewhere – owing to perception’s passivity, it cannot be straightforwardly analysed as a case of the body undergoing a change by the agency of the soul as its unmoved mover. Nevertheless, Aristotle maintains in (vii) that, after reformulating the first premise along the lines of the Causality of Soul (purified from Cause/Subject), we can accept the characterization of perception as ‘undergoing a change’ – namely, as we know from An. 1.3, as ‘undergoing a change by the agency of perceptual objects’, and yet we can resist the conclusion that the soul itself undergoes a change. Aristotle insists that not even in the case of perception does the change take place ‘in the soul’.

This important statement will be crucial for any attempt at resolving the apparent inconsistency outlined in Section 5.1. However, the achievement of (vii) ought not to be overestimated. It is largely programmatic: while claiming very clearly that the characterization of perception as a kind of undergoing a change by the agency of perceptual objects does not commit one to the view that the soul itself undergoes a change, Aristotle’s assertion comes short of even hinting at what the alternative account of the soul’s role in perception could be. He analyses perception as a change extending up until the soul (μέχρι τῆς ψυχῆς), but he does not say how the soul itself is involved. Furthermore, it is unsafe to read much into the preposition here, for Aristotle is, effectively, just mimicking Plato, while insisting that the conclusion drawn by Plato from this analysis of perception is a non sequitur.Footnote ²⁸ In the Timaeus, Plato spoke of changes coming from both coloured and sounding objects as ‘extending up until the soul’ (μέχρι τῆς ψυχῆς);Footnote ²⁹ and he also described them as ‘falling upon the soul’, implying apparently that these changes are received by the soul so as to become changes of the soul itself, in line with the Platonic Formula.Footnote ³⁰ In (vii) Aristotle seems to be claiming that we can take over the former characterization, while rejecting the latter. But at the present stage of inquiry, this claim can be doing nothing more than laying down a key desideratum, as there is not even the slightest hint at any alternative account of the soul’s involvement. This, after all, is not very surprising given that we are still in the aporetic Book 1.

Although we should certainly not overestimate the achievement of (vii), it would be equally mistaken to underrate its significance. This is the passage in which Aristotle addresses the most reasonable candidate for a case of the soul itself undergoing a change flagged at An. 1.3, 406b10–11 and, as such, it is the only passage that certifies the generality with which he formulates the conclusion at An. 1.4, 408b30–1 that ‘the soul cannot undergo any change whatsoever’ (restated again at 1.5, 411a24–26). Although Aristotle does not spell out how the soul is responsible for perception as the unmoved principle ‘up until which’ the changes extend, he seems to be staking a lot on the feasibility of this model. Effectively, his stake is on a robust Impassivity of Soul_P.

If the canvassed reading of An. 1.3–4 is on the right track, then it puts considerable pressure on the question of the consistency of Aristotle’s account – particularly when combined with a non-deflationary understanding of the Passivity of Perception. By accepting these two tenets, Aristotle seems to be committed to rejecting Cause/Subject in the case of perception too. The problem is to see how he can do so. This difficulty, however, has been rarely recognized as such, because, since antiquity, interpreters have most often tended to compromise either the Passivity of Perception or the Impassivity of Soul_P – apparently because they believed that, in the specific case of perception, it is impossible to abandon Cause/Subject entirely. This, to be sure, is exactly what Aristotle seems to be doing in An. 1.3–4 (particularly in (vii)); but interpreters have often tended to interpret the upshot differently, as if Aristotle was not aiming at overcoming Cause/Subject_P, but at either essentially qualifying the Passivity of Perception or accepting the implication that some kind of Passivity of Soul_P is unavoidable.

In the following two sections, I examine more closely these two strategies, which can be traced back to Alexander of Aphrodisias and Themistius, respectively.Footnote ³¹

5.3 Perception Is Not Passive (Alexander of Aphrodisias)

Alexander of Aphrodisias seems to have been largely in agreement with the reading of An. 1.3–4 sketched out above – at least insofar as Aristotle’s commitment to the Impassivity of Soul_P is concerned. On this point, Alexander takes the message of An. 1.3–4 to be unambiguous. The soul ‘cannot undergo any change in its own right (ἀκίνητον καθ’ αὑτήν)’,Footnote ³² and this concerns any conceivable kind of change (κίνησις), the perceptual change included: ‘For neither the [changes] in perception and imagination …, which are alterations, nor the spatial [motions], are changes of the soul itself (τῆς ψυχῆς εἰσι κινήσεις καθ’ αὑτήν), but rather of the compound.’Footnote ³³ Nothing is taken away from this conclusion by Aristotle’s analysis of perceptual κινεῖσθαι and πάσχειν in An. 2.5–3.2: in whatever way these notions are to be spelled out, they cannot be ascribed to the soul itself.Footnote ³⁴

However, it is far from clear on such a reading how the soul can be involved in perception. Alexander thinks that this question can be answered only if we realize that the identification of perceiving as a kind of undergoing a change by the agency of perceptual objects (accepted in An. 1.3–4) is strictly speaking incorrect. The perceptual changes or affections are only bodily preconditions of perceiving proper – they are how perceiving ‘comes about’. Perceiving itself, however – and this is crucial – cannot be classified as any kind of being changed or affected. In this sense it is not passive, although Aristotle might seem to be characterizing it that way. Alexander is very clear about this point when correcting Aristotle’s numerous assertions that perceiving is a kind of being affected. The fact that Aristotle begins from such a claim in An. 3.4 (429a13–18), for instance, is interpreted by Alexander in the following way: neither νοῦς nor the perceptive soul is itself affected (An. 84.3–4),

We must distinguish between ‘perceiving itself’ (i.e. what perceiving essentially is) and the preconditions of perceiving (i.e. how it comes about) according to Alexander because, while the story of ‘coming about’ will be a story of being affected and changed, perceiving itself must be defined as something else – namely, discriminating (κρίνειν). And this distinction leads us directly to Alexander’s answer to the question about the role of the perceptive soul: while the perceptive organs are affected by perceptual objects, the soul discriminates them without itself being in any way affected. Alexander repeats this point time and again, especially in a long stretch of his own De Anima (60.19–65.2) drawing on Aristotle’s De Anima 3.2, 426b8–427a16.

This passage contains, among other things, Alexander’s considered way of spelling out the model laid out at An. 1.4, 408a34–b18,Footnote ³⁶ which holds that the media ‘hand over’ (διαδιδόναι)Footnote ³⁷ the changes or affections to the peripheral organs, which in turn ‘hand them over’ to the central organ, although the central organ does not ‘hand them over’ to anything else, but rather ‘sends’ (διαγγέλλειν) them to the soul. This terminological difference seems to signal that the soul does not take these changes over, but rather discriminates (κρίνειν) them and thereby discriminates the perceptual objects causing these changes.Footnote ³⁸ Throughout the passage, Alexander’s point seems to be that because perceiving itself does not consist in being affected, nothing prevents us from ascribing it, under its essential (or formal) definition as a case of discrimination, to the soul itself.Footnote ³⁹

A part of the motivation behind this claim may come from the Hellenistic and post-Hellenistic intuition about being active (ἐνεργεῖν) as the opposite of being affected (πάσχειν):Footnote ⁴⁰ as an activity – and, indeed, a complete activity – perception cannot be itself a case of being affected. But it is Alexander’s acceptance of Cause/Subject_P that seems to lie at the core of his strategy. Taking Aristotle’s classification of perceiving as a kind of being affected as it stands would imply that the perceptive soul is itself affected by perceptual objects, and that cannot be so. Thus, Aristotle’s classification must not be taken as it stands – in fact, it does not tell us anything about what perception is, it only captures the way in which perception ‘comes about’.

This strategy encounters obvious exegetical difficulties when it comes to Aristotle’s numerous assertions to the effect that perception is a kind of being affected by and assimilated to perceptual objects; so it is hard to resist the impression that Alexander is engaged in a project of correcting Aristotle. But Alexander’s strategy is also confronted with philosophical difficulties; indeed, it helps to bring out difficulties that are not immediately obvious, but that any approach endorsing the Impassivity of Soul_P as defended in An. 1.3–4 must face.Footnote ⁴¹ To put it bluntly, any such approach must face the following question: if the perceptive soul is to remain impassive, how can it ever ‘get the message’ that the perceptive organs are ‘sending’ to it? That is, first, how can it ‘understand’ the message, and, second, how can it ‘know’ at all that some such message is ‘being sent’ to it right now? Or, in a less metaphorical language: how does it come to be that the perceptive soul discriminates an external perceptual object and that it discriminates exactly the perceptual object that is now acting on the organs, if the soul is itself in no way affected by it? The concern here is directly related to the one raised by Aristotle against Anaxagoras:Footnote ⁴² it is unclear how something entirely impassive can come to know or discriminate anything and, a fortiori, to discriminate this or that particular object right now.

One may think that there is a simple response to this kind of query: we discriminate the object acting on our organs because discrimination is the form of perceiving whose matter is exactly the perceptual affections received by the organs.Footnote ⁴³ However, in fact, this is just another way of formulating the question, for once discrimination as an ‘activity’ is contrasted with the ‘affections’ reserved to the body, the question is exactly how one can be ‘the form of’ the other.Footnote ⁴⁴ Furthermore, since discrimination clearly has to do with the soul (as the primary cause of perception), the question is what difference the soul makes – that is, how it is responsible for the fact that the affections caused by perceptual objects and transmitted through the body lead to a discrimination of those objects rather than, say, just to a (failed) mediation. Alexander’s answer seems to be that it is the perceptive soul itself that discriminates affections and, through these, the perceptual objects. But this only begs the question. The most charitable reading of Alexander’s claim seems to be that the soul is primarily responsible for the fact that the bodily affections acquire the form of discrimination; again, though, the question is exactly how.

At this point, readers who lean towards a Rylean understanding of Aristotle may wish to say that I am making too much of Alexander’s talk of ‘sending’ and that his assertions to the effect that the perceptive soul itself discriminates, as numerous as they are, should be taken with a pinch of salt: strictly speaking it is, of course, the man who discriminates on account of the perceptive soul. That is fair enough. Perhaps Alexander omitted any talk of ‘sending’ in his lost commentary on Aristotle’s De Anima, and perhaps he even refrained from ascribing the activity of discrimination to the perceptive soul itself (although I doubt the latter). The point is that simply refraining from this would bring Alexander no closer to a satisfying solution; it would merely make the key question less apparent. Let us take for granted that it is not the soul itself that discriminates, but an individual man ‘on account of the soul’.Footnote ⁴⁵ This is a loss, not a gain, because, before, we at least had a name for how the soul is involved (albeit not a very helpful one).Footnote ⁴⁶ If we just say that the man discriminates on account of the soul, we must then ask: on account of the soul doing what? Aristotle is confident that he has an answer to this question with regard to animal locomotion, and, mutatis mutandis, to passions or nutrition (although the details are somewhat thorny): the animal moves itself because the soul moves its body without itself being moved. But what does the soul do when the animal perceives? It is a Rylean error to think that one can save Aristotle by simply ignoring this question.

When we take the question seriously, the most intuitive way of answering it, on the same level of generality, will surely be this: the animal perceives because the soul is changed or affected by the perceptual object. But this is exactly what Aristotle seems to forbid us from saying in An. 1.3–4. It is to Alexander’s credit that he has very much emphasized this point and it is also to his credit that his texts bring out just how difficult it then becomes to reconstruct Aristotle’s account consistently. In the following section, we turn to the family of strategies that start exactly from rejecting this point.

5.4 The Perceptive Soul Is Not Impassive (Themistius)

The alternative starting point can be expressed by saying that ‘the soul [of the perceiver] is involved in being affected along with the organs’: the soul gets the message in the straightforward sense of receiving the changes or affections into itself as a proper subject of them. This allows one to take Aristotle’s classification of perception as a kind of being affected quite literally: perceiving, indeed, is a kind of being affected and altered by perceptual objects, but a very special kind of it, owing exactly to the fact that ‘the soul is affected along with the organs’. On account of this passivity of the soul, we may say, perception becomes a discriminative kind of being affected, a way of being affected by perceptual objects such that these objects are discriminated in it.

The quoted phrase comes from ThemistiusFootnote ⁴⁷ and encapsulates what is distinctive of his approach to the seemingly inconsistent triad of tenets. Like Alexander, he seems to be taking Cause/Subject_P for granted. Unlike Alexander, he takes perception to be essentially passive. This unavoidably leads him to conclude that the perceptive soul cannot be as impassive as it first seems to be from An. 1.3–4. Themistius’ interpretation is interesting because (unlike many later interpreters) he is acutely aware of how precarious it is, both exegetically and philosophically. Indeed, it can be shown that his reasons for compromising the Impassivity of Soul_P go beyond purely interpretative concerns and are motivated by developments in the philosophy of perception close to Themistius’ own lifetime.

Throughout his paraphrasis of An. 1.3–4, Themistius is responding to a Neo-Platonist account of perception that ‘a critic of Aristotle’ has defended against Aristotle’s argument. The catchword of this opposing account is that perception is ‘a self-motion of the soul’. The thrust of the critic’s objection is that Aristotle was wrong to treat perception as a phenomenon that ‘most reasonably’ suggests that the soul undergoes a change by the agency of something else, namely of perceptual objects. Rather:

The relevant changes or motions (κινήσεις) ‘of the soul’ coming ‘from the soul’s essence’ are spelled out as ‘discriminations’ (κρίσεις).Footnote ⁴⁸ Furthermore, the critic is reported to have likened perception to walking, where the walker stands for the soul and the ground on which she walks stands for the perceptual objects.Footnote ⁴⁹ In Themistius’ eyes, this account is ‘ridiculous’ and it only shows that the idea of an entirely impassive perceptive soul is a non-starter. Themistius agrees that perception involves a ‘motion’ (κίνησις) of the soul, and so he thinks that the only way to defend a genuinely Aristotelian account of perception against the Neo-Platonist speculation is by insisting that in perception both the body and the soul are ‘being moved’ by perceptual objects.Footnote ⁵⁰

When Themistius comes to the ‘Rylean passage’, he acknowledges that his interpretative approach faces difficulties. He is perfectly aware that his great predecessor, Alexander of Aphrodisias, took the passage as expressing Aristotle’s commitment to the Impassivity of Soul_P, and that the ‘critic’ seems to have followed Alexander’s lead. Themistius, however, opposes this interpretative claim by referring to later chapters of De Anima, particularly An. 2.5 introducing the preservative πάσχειν and An. 3.7 where – on Themistius’ reading – Aristotle characterizes perception as ‘a different kind of motion/change (κίνησις)’.Footnote ⁵¹ In those later chapters, according to Themistius, Aristotle distinguishes between two kinds of ‘being moved’, one of which can indeed be ascribed only to bodies, while the other defines exactly the way in which one can talk about the soul itself being moved by perceptual objects. The exegetical proposal is that, in An. 1.3–4, Aristotle is considering only the first kind of motion. His endorsement of the Impassivity of Soul_P here thus requires strong qualification:

To put it bluntly, whereas Alexander argued that An. 1.3–4 necessitates a qualification of Aristotle’s claim in An. 2.5ff. that perception is a kind of being affected, Themistius argues that An. 2.5ff. develops such a notion of being affected and being moved that it allows us to qualify the claim from An. 1.3–4 that the perceptive soul is unmoved and impassive and to meaningfully assert, in Aristotle’s name, that the soul itself is moved by perceptual objects.

Recent scholars have added further support to this approach developed first by Themistius. It was argued that in An. 2.5 Aristotle is explicit about intending to define precisely the kind of being affected and being altered applicable to the perceptive soul: the subject of his discussion is τὸ αἰσθητικόν, and τὸ αἰσθητικόν means the perceptive capacity of the soul.Footnote ⁵³ I have already suggested that (a) comparison with An. 2.4 warrants caution in expecting An. 2.5 to say something specific about the role of the soul (Sections 1.1 and 3.7) and that (b) the first occurrence of the expression τὸ αἰσθητικόν in An. 2.5 suggests that Aristotle means more broadly ‘that which can perceive’, prior to any hylomorphic analysis into the perceptive body and the perceptive soul (Section 2.4). As regards the wider context of Aristotle’s use of the expression τὸ αἰσθητικόν: (c) it is noteworthy that even in An. 2.1–3, which is cited as the crown witness of this approach, Aristotle does not shy away from using the adjective αἰσθητικόν to refer to perceptive bodies;Footnote ⁵⁴ (d) when Aristotle uses parallel expressions (τὸ γευστικόν, τὸ ἁπτικόν, and the like) in An. 2.7–11 and applies the assimilation model to them, he seems always to refer to perceptive bodies;Footnote ⁵⁵ (e) when summing up the inquiry of An. 2.5–3.2 Aristotle does so in terms of asking about the principle on account of which the animal as a whole is said to be perceptive (αἰσθητικόν).Footnote ⁵⁶ Interestingly, the forefather of this approach, Themistius, agrees with these findings.Footnote ⁵⁷ There are, to be sure, other passages in the De Anima that may seem to suggest that Aristotle does, after all, allow the perceptive soul itself to be affected by and/or assimilated to perceptual objects,Footnote ⁵⁸ but I shall argue that none of them actually implies this.Footnote ⁵⁹ For now, I want to add a few comments on why the Themistean approach is problematic, specifically with respect to Aristotle’s argument at An. 1.3–4.

First, Themistius’ solution stands or falls with his distinction between psychic and bodily motions/changes (κινήσεις). But not only is this distinction absent from An. 1.3–4, it also appears to be philosophically dubious. It threatens to assimilate soul to bodies in the way in which Plato arguably did and that Aristotle was eager to overcome. Moreover, some of Aristotle’s arguments in An. 1.3 can be turned against Themistius’ view, beginning with the argument at 406a12–22: something can be itself moved and altered only if it is itself in a place – but it is a category mistake to ascribe a place to the soul.Footnote ⁶⁰

Second, Themistius’ interpretation of An. 1.3–4 threatens to undermine the core of Aristotle’s argument against Plato – exactly along those lines intended by ‘the critic of Aristotle’. Aristotle complains that, by ascribing motion/change (κίνησις) to the soul, Plato assimilates it to bodies (so that his account can be treated on a par with that of Democritus).Footnote ⁶¹ But this objection loses most of its power once Aristotle is read as himself relying on a distinction between psychic and bodily motions with regard to perception. Plato obviously wants to ascribe psychic and not bodily motions to the soul (as ‘the critic’ duly stresses). Accordingly, if Aristotle’s point in An. 1.3–4, as Themistius argues, is just that the soul cannot be moved with bodily motions, then his criticism of Plato is undermined, because Plato would fully agree.Footnote ⁶² This might be a welcome result for someone like Themistius who aspires, to a large extent, to reconcile Plato and Aristotle, but it does not offer a very charitable reading of An. 1.3–4.

One could attempt to resist this conclusion in the following way.Footnote ⁶³ In An. 1.3–4, Aristotle’s criticism is not directed against the idea of ascribing bodily motions or changes to the soul (as Themistius says somewhat ineptly), but rather against the idea of ascribing ordinary changes to the soul. This is what Plato does and what Aristotle prevents. It is by failing to distinguish the kind of changes applicable to the soul from the ordinary changes that Plato assimilates the soul to the body. But, while Aristotle prevents ascribing ordinary changes to the soul, he is free to ascribe non-ordinary changes to it as defined in An. 2.5. In this way, Aristotle would not be simply relying on a distinction between bodily and psychic changes. Rather, he would be developing a distinction between two kinds of changes that are defined independently of whether they belong to the body or to the soul. Thus, his criticism of Plato could stand insofar as the latter lacks Aristotle’s technical distinction between two kinds of change.

Against this line of defence, one can imagine someone like Alexander raising two kinds of objections. First, Aristotle’s argument in An. 1.3–4 would still be somewhat disappointing. Several of the concepts introduced here would, to say the least, lose their power. The distinction between undergoing a change in its own right and undergoing a change coincidentally would play no significant role in the case of perception, for both the body and the soul would be undergoing a change in their own right, albeit a different kind of change in each case. Indeed, the point of the ‘Rylean passage’ concerning perception would verge on an empty truism: stating that a perceptual change reaches up until the soul but is not a change of the soul would simply mean that when it enters the soul it is no longer a change of the body but becomes a change of the soul. The way Aristotle proceeds would be utterly confusing: instead of pointing out (as Themistius would want him to) that there is no difficulty in saying that in perception the soul itself is undergoing a change, once we realize that this is a special kind of change, Aristotle would have to be understood as gratuitously misleading the reader by flatly denying any change to the soul, without bothering to indicate that he means only a certain kind of change.Footnote ⁶⁴

Second, some of Aristotle’s arguments in An. 1.3–4 would still threaten to undermine his own position. It is not clear why the non-ordinary changes should be exempt from the requirement that the subject of a change itself be in a place. After all, Aristotle never lifts the demand raised in GC 1.6 that the subject of being affected must be in contact with the agent; and being in contact presupposes being in a place.Footnote ⁶⁵ However, we have seen that, by Aristotle’s lights, it is absurd to conceive of the soul as itself being in a place.Footnote ⁶⁶ Moreover, at An. 1.3, 406a30–b3, Aristotle seems to anticipate the move that Themistius recommends, and he argues against it. If the alleged changes of the soul are to explain the changes of the body produced by the soul (as all sides agree), then, Aristotle argues, they must be the same kind of changes, otherwise talking about ‘changes’ of the soul is idle.Footnote ⁶⁷ Aristotle’s reasoning here will apply mutatis mutandis to perception: if the involvement of the soul in perception is to be analysed in terms of the soul itself undergoing the changes transmitted by the body, then what is transmitted through the body and what is received by the soul must be the same kind of change; otherwise, the assumption will be idle or will beg the question. Aristotle can thus be understood as anticipating the idea of distinguishing between ‘bodily’ and ‘psychic’ changes – and denouncing it as a piece of sophistry.Footnote ⁶⁸

Accordingly, An. 1.3–4 contains serious reasons against adopting the Themistean strategy. What Themistius seems to be doing is effectively returning – or at any rate coming very close to – the conception, encapsulated in the Platonic Formula, that Aristotle set out to overcome in An. 1.3–4. Another, independent, reason against adopting this strategy is provided by An. 2.5 itself, at least if the interpretation of it developed in Chapters 1–3 was on the right track. By spelling out the role of the soul in terms if it being itself, together with the body, the subject of the relevant kind of change resulting in a likeness to the perceived object, Themistius is effectively giving up on understanding the dynamic nature of this likeness. If what happens at time t of perceiving F is that both the organ and the soul are F, there remains nothing that could explain how the perceiver can be further affected by F at t, and so perceptual contact will be lost.Footnote ⁶⁹

Alexander’s approach to An. 1.3–4 appears to be more faithful to the programme formulated in this portion of the treatise than Themistius’, and he succeeds, unlike Themistius, in avoiding the problem of losing perceptual contact. However, his interpretation gets into other kinds of difficulties of its own, sketched out in the preceding section. Moreover, I shall contend that it is in fact not sufficiently faithful to Aristotle’s programme, either. This is the case because Aristotle not only aims at advocating the Impassivity of Soul_P but also intends – as rightly emphasized by Themistius – to account for the Passivity of Perception. So, Aristotle’s programme turns out to be more ambitious than either of the two sides recognizes, as shown by his rejection (most explicit in the ‘Rylean passage’) of Cause/Subject – even for the case of perception.

5.5 The Soul as an Efficient Cause of Perception

The dilemma that divides Alexander and Themistius did not disappear with antiquity. A very similar set of questions can be seen in the medieval debate concerning the so-called agent sense. Inspired by an obiter dictum in Averroes’ Long Commentary on De Anima,Footnote ⁷⁰ some Latin thinkers defended the existence of a sensus agens, parallel to the ‘agent intellect’ (from An. 3.5), as a necessary causal ingredient in any act of perceiving. The argument could proceed quite far along the lines already familiar to us from Section 5.3.Footnote ⁷¹ The soul, as the proper cause of perception, cannot simply be itself affected by the body,Footnote ⁷² so perceiving (sentire) cannot be itself any kind of ‘being affected’ (pati). Rather, it must be a kind of acting (agere) – that is, ‘producing perception’ (efficere sensationem) or judging (iudicare) – for which ‘being affected’ – that is, receiving the perceptual species – is only an enabling condition. The soul is thus a productive cause (causa activa) of perception.Footnote ⁷³ The most striking difference between this view and Alexander’s position is the systematic employment of the idea of the perceptive soul as a sensus agens, that is, as an efficient cause of perception. However, in the form just outlined, this approach seems to face similar kinds of difficulties to those faced by Alexander: we would like to know what exactly the soul is doing as the primary cause of perception, but the only answer we seem to get is that it produces perception, which makes the approach look suspiciously circular.Footnote ⁷⁴

On the opposite side of the medieval debate, we find thinkers such as William of Auvergne and Thomas Aquinas who have little patience with the idea of an agent sense. They claim, instead, that the only agent of perception is the external perceptual object, and perception just is a way of being affected by and assimilated to it (albeit a very special way).Footnote ⁷⁵ This insistence on the Passivity of Perception then standardly leads to compromising the Impassivity of Soul_P in a way that is also already familiar to us. Indeed, in his commentary on An. 1.3–4, Aquinas seems basically to be repeating Themistius’ points. When it comes to the ‘Rylean passage’, he insists, like Themistius, that Aristotle cannot intend to deny without qualification that the soul can be moved. What he must mean, instead, is that it cannot be moved with any ‘motion of a natural kind’ (motus secundum esse naturale) such that only bodies can undergo. If this is the point, it leaves open the option, to be developed in later chapters, that the soul is in fact moved with ‘motions of a spiritual kind’ (motus secundum esse spirituale).Footnote ⁷⁶

This medieval debate is, obviously, even further beyond the scope of the present study than the ancient debate briefly summarized in Sections 5.3 and 5.4. The reason for bringing it up is not only to show how the ancient dilemma continued to divide interpreters of Aristotle; the thesis of the so-called ‘agent sense’ is also interesting for us because it introduces into the discussion a new element – with a more solid support in Aristotle than is often recognized – which may open a path out of the dilemma that has concerned us in this chapter. It is worth noting that Jandun’s version of sensus agens, sketched out schematically above, takes a recognizably different direction from the famous passing remark of Averroes. In Jandun’s view, the reception of perceptual species is explained purely in terms of the agency of perceptual objects, while the role of the agent sense is limited to producing a ‘perceptual cognition’ of them.Footnote ⁷⁷ Averroes, in contrast, introduced the idea of a second agent of perception – distinct from the perceptual object – as a possible response to a doubt one may have about the very idea of a species or ‘intention’ as a different mode of presence, in the perceiver, of the form that is materially present in the perceptual object. Averroes’ doubt can in fact be taken as an additional potent objection against the Themistean strategy: saying that an ensouled organ, or even the soul itself, receives the form in a different mode of being (i.e. ‘psychically’ or ‘spiritually’) merely begs the question, because this difference of being cannot be explained by a difference of what the form is received in. What needs to be accounted for, instead, is how its mode of being is transformed in the first place, so that it can be received in a different kind of substrate.Footnote ⁷⁸ It is exactly because we must explain how there can be something like a species or ‘intention’ that is received by a perceiver that we need to posit, according to Averroes, another agent – besides the perceptual object – which is responsible for this transformation. This is the case because, on his view, only something actual in the relevant respect, and not a merely potential substrate, can actualize the potentiality on the side of perceptual objects for becoming a species.Footnote ⁷⁹

More than two centuries after the main debate, Jacoppo Zabarella still finds it appropriate to dedicate an entire section of his commentary on Aristotle’s De Anima to the question of the sensus agens.Footnote ⁸⁰ Furthermore, he seems to come at least somewhat closer to Averroes’ original position than Jandun in insisting that the form of the perceptual object is properly received only once the soul has acted upon it and ‘absorbed’ it into its discriminative act.Footnote ⁸¹ Unfortunately, Averroes’ passing remark does not allow us to extract any full-fledged account, and he himself acknowledges the difficulty of the task.Footnote ⁸² Moreover, the parallel with the ‘agent intellect’ from An. 3.5, decisive for the whole Latin debate down to Zabarella, seems unfortunate in suggesting that there are two different kinds of sense: a passive and an agent one.Footnote ⁸³ What makes Averroes’ famous remark nonetheless interesting for our purposes is that we can disregard the idiosyncrasies of the Latin reception and see Averroes’ reflection as providing an alternative framework for addressing the dilemma that has concerned us in the present chapter.

Averroes’ insistence that a difference of substrate cannot explain a difference of what is received in it, and that a second agent is required already on the level of reception, can be read as perfectly neutral both on whether the soul is itself affected, and on whether perception is essentially passive. Accordingly, the idea of a second agent may allow us to develop Aristotle’s account of perception in a way that would avoid compromising either the Impassivity of Soul_P, or the Passivity of Perception.

In fact, as noted above, there is solid support in Aristotle for the idea of a second agency involved in perception and ascribed to the perceptive soul. There are two passages in which Aristotle seems to describe the soul as an efficient cause of perception characterized as a kind of alteration. One of them comes as a part of Aristotle’s official statement in An. 2.4 on the different senses in which the soul is to be understood as the cause of life in ensouled bodies:

Not surprisingly, Zabarella puts much emphasis on this passage as a key support for Aristotle’s commitment to the idea that the perceptive soul is an efficient cause of perceiving.Footnote ⁸⁴ It is also not surprising that interpreters following the Themistean strategy are usually silent about this passage.Footnote ⁸⁵ It seems impossible for the soul to be the subject of an alteration of which it is an efficient cause, at least if we stick to Aristotle’s account of agency in Phys. 3.3 as an activity of the agent in the patient (and unless we commit Aristotle to Jandun’s idea of two distinct kinds of sense).

The context of the quoted passage from An. 2.4 is worth emphasizing. Aristotle begins from his official quadripartition of causes and, excluding material causality as a role that would be inappropriate for the soul, he works through the other three kinds one by one. It is obvious that he wants to communicate something by insisting that over and above being a formal and a final cause,Footnote ⁸⁶ the soul is also an efficient cause and is so even in the case of perception. Nor should we be discouraged by Aristotle’s cautious formulation that perception is a kind of alteration that is ‘due to the soul’ (κατὰ ψυχήν) – as if he were backing away from classifying the causality in question as genuinely efficient.Footnote ⁸⁷ First, he uses exactly the same phrase to capture the relation of the soul to growth, and he treats growth and diminution (together with nutrition) here as directly parallel to perception as far as the kind of causality of the soul is concerned. This confirms that ‘being due to the soul’ is nothing short of describing the soul as an agent acting on the body, for this is unambiguously the role that Aristotle will ascribe to the soul in nutrition later in An. 2.4 (416b20–3).Footnote ⁸⁸ Second, Aristotle repeats the same point in PA 1.1, where his expression contains no such ambiguity: the perceptive part of the soul is characterized as a principle of change (κινήσεως ἀρχή) – namely, a qualitative change (ἀλλοιώσεως). Against the background of An. 2.4, it appears very likely that the kind of qualitative change Aristotle has in mind is just the one that perception was identified with at 415b24 (and elsewhere).Footnote ⁸⁹

Given Aristotle’s general reticence in the De Anima with regard to spelling out the precise role of the soul in the relevant activities,Footnote ⁹⁰ the present passage (combined with PA 1.1) should be taken very seriously as providing strong evidence of his considered view on the matter. However, this has rarely been done, which seems largely to be because of the difficulty inherent in the issue. The idea of understanding the soul as an efficient cause is challenging and controversial on its own,Footnote ⁹¹ and the difficulties multiply exponentially when we start to ask specifically about the way in which Aristotle intended to apply the model of impassive efficient causes to the perceptive soul, particularly because an efficient cause of perception has already been identified in the perceptual object. Accordingly, it is not very surprising that little has been written on the matter since Zabarella.

On the one hand, we find accounts in which an efficient causality is ascribed to the soul in relation to perception, but not in the sense of making the perceptive soul an efficient cause of perception itself. Thomas Johansen developed such a view, wherein the perceptual range of each sense is being actively adjusted (when, for instance, on a bright day one enters a dark cave),Footnote ⁹² and he offered a minimalistic interpretation of how the soul is indirectly an efficient cause of perception, drawing on An. 2.5, 417b16–18. From the observation that the development of the perceptual apparatus is initiated by the sperm, but once the heart has been formed it is the individual soul that governs and completes this development, Johansen infers that ‘the sense-object only brings to the final stage of activity a series of changes in the animal of which the animal has itself, from conception on, been the efficient cause’.Footnote ⁹³ Moreover, Klaus Corcilius and Pavel Gregoric have offered a detailed account of how perception can be the efficient cause of thermic alterations around the heart that lead to animal locomotion.Footnote ⁹⁴

On the other hand, some scholars have affirmed that, according to Aristotle, the perceptive soul is, indeed, an efficient cause of perception itself, but without spelling out the details or at least showing how this could be done.Footnote ⁹⁵ The only exception in this respect, to my knowledge, is a paper by Klaus Corcilius: although he does not explicitly refer to the idea of the soul being an efficient cause of perception, he does offer a detailed, non-circular account of, as he puts it, the soul’s ‘causal role in the production of phenomenal content’.Footnote ⁹⁶ One advantage of Corcilius’ account over Zabarella’s (which is based on the ambiguous notions of ‘emanation’ and ‘absorption’)Footnote ⁹⁷ is that it draws on Aristotle’s own notion of a discriminative mean, as introduced in the final passage of An. 2.11.Footnote ⁹⁸

The aim of the cursory overview of the history and the textual basis for the idea of an agent sense provided in this section was to suggest that this idea may open a perspective on our dilemma that is yet to be systematically explored. It is true that the idea can easily collapse into a position akin to Alexander’s, with all its difficulties and perhaps even more, but this need not be the case. The mark of progress on this topic, I submit, would be if we succeeded in spelling out the agency of the soul in a non-circular way. That is, if we succeeded in describing – in at least as informative a way as that which is provided by the conception of the soul as the unmoved mover of locomotion, passions, and nutrition – the soul’s role in perception. The task would be to explain by doing what the soul is responsible for animal perception without compromising either the Impassivity of Soul or the Passivity of Perception and without taking anything away from the status of perceptual objects as the primary agents of perception. This is exactly what Chapter 7 will attempt to do.

However, before embarking on this endeavour, we must further prepare the ground by inquiring into Aristotle’s notion of discrimination (κρίνειν) and of the ‘discriminative mean’ in Chapter 6.