1.1 The Passivity of Perception

Among the numerous passages attesting to Aristotle’s willingness, in the De Anima and beyond, to classify perception as a kind of being affected (πάσχειν),Footnote ¹ one of the most telling comes at the outset of his inquiry into the thinking part of the soul in An. 3.4:

It is significant that, when summarizing his account of perception in this new context, the very first feature that Aristotle underscores is its passivity.

This fact has, unfortunately, been somewhat obfuscated by difficulties surrounding the point behind Aristotle’s disjunction in (i). Perhaps, one might think, he wants to say that thinking is not really a kind of being affected, but only resembles it.Footnote ³ And perhaps he is implying that this was already true for perception.Footnote ⁴ These readings, however, are undermined by how Aristotle proceeds in the chapter. When he comes to formulate a puzzle about thinking as a kind of being affected at 429b22–6, he simply drops the second disjunct. Furthermore, in his response to the puzzle, he reaffirms the classification (again without any mention of the second disjunct).Footnote ⁵ This suggests that the disjunction is neither intended to draw a contrast between perception and thought, nor meant to call their classification as cases of being affected into question. To understand the point behind the disjunction, we must return to Aristotle’s account of perception. I shall argue that he is referring us all the way back to An. 2.5.

As soon as passivity is in place in (i), Aristotle further infers from it a series of three characteristics pertaining to νοῦς in (ii)–(iv). The last two of these features are rather clearly drawing on Aristotle’s second general account of perception in An. 2.12.Footnote ⁶ What is significant here is that receptivity is introduced as following from, or further building on, the relevant notion of passivity. We shall see that this order encapsulates something important about the relation between Aristotle’s two general accounts of perception in An. 2.5 and 2.12.

The case of (ii) – that is, impassivity – is somewhat more puzzling. There is no passage within Aristotle’s account of perception in An. 2.5–3.2 that explicitly establishes the claim that ‘that which can perceive’ (τὸ αἰσθητικόν) is impassive. Moreover, the whole idea of inferring impassivity on the part of perceivers (or thinkers) from the passivity of perception (or thinking) seems paradoxical.Footnote ⁷ This is what has led to the scholarly suggestion that we see here, again, a contrast between perception and thought.Footnote ⁸ But this suggestion is even more powerfully disproved by what follows in An. 3.4. Aristotle returns to discuss impassivity at 429a29–b5 in order to argue that ‘the impassivity of that which can perceive and that which can think is not the same’ (429a29–30). This is a rather obvious qualification of (ii), which shows that the claim made in (ii) was not yet intended to draw out a contrast between perceiving and thinking. This is further confirmed by the logic of Aristotle’s second inferential step in the quoted passage: impassivity is derived together with (iii) and (iv), which clearly draw on established major features of perception. This underscores the question about where Aristotle believes impassivity has been established.Footnote ⁹ I shall argue that in (ii) Aristotle still has An. 2.5 in mind, though in this case we cannot fully understand his point without comprehending how his first general account of perception is set within a dialogue with his predecessors (as developed in Book 1), including Anaxagoras and his theory of an impassive νοῦς.

Let us now turn to examine how Aristotle’s first general account of ‘all perception’ (416b32–3) is introduced in An. 2.5. He starts from the observation that perception ‘comes about in being changed (κινεῖσθαι) and being affected (πάσχειν), as has been said’, for (γάρ) ‘it seems to be an alteration (ἀλλοίωσίς τις)’ (416b33–4).Footnote ¹⁰ The thought here is not altogether transparent, but it seems safe to say at least that it indicates the central focus of Aristotle’s first general account. Throughout the chapter, he is engaged in investigating how the notion of being affected as well as the related notions of being changed and being altered apply to perception, and how they contribute to capturing what exactly perception is. The notion of being affected is omnipresent in An. 2.5 and the chapter contains the only explicit passage in De Anima – and, indeed, in the Aristotelian corpus as a whole – distinguishing different kinds of being affected (417b2–5).Footnote ¹¹ Moreover, the chapter closes (418a3–6) with nothing other than a full-fledged account of perception as a kind of being affected by, and assimilated to, the perceptual object. Furthermore, immediately before this closing passage, Aristotle insists (at 417b32–418a3) that, after drawing the requisite distinctions, it is admissible, and indeed necessary, to use the notions of ‘being affected’ and ‘being altered’ (ἀλλοιοῦσθαι) as ‘proper terms’ (κύρια ὀνόματα) when talking about perception, claiming that this should be done despite the fact that the usual narrow notions of ‘being affected’ and ‘being altered’ have turned out to be unsuitable.Footnote ¹² It is here, I shall argue, that we find the background necessary for understanding Aristotle’s disjunction in (i) above.

While one can hardly deny that An. 2.5 provides the central source for understanding the sense in which perception is passive, there have been widely diverging views on what exactly this passivity amounts to. We can distinguish four main approaches:

• Material Interpretation. Some interpreters have thought that ‘being affected’ refers only to a necessary condition or to the material component of perception, such as any bodily changes presupposed by, or involved in, the activity of perceiving.Footnote ¹³

• Deflationary Interpretation. Other scholars have claimed that ‘being affected’ in the relevant sense captures only the transition from not perceiving to perceiving and, in general, from not φ-ing to φ-ing, where φ-ing does not need to be passive in any sense whatsoever (as supposedly manifested by the example of housebuilding at 417b9).Footnote ¹⁴

• Psychic Interpretation. Still other scholars have understood the notion of being affected as capturing the specifically ‘psychic’ aspect of perception in contrast to its ‘bodily’ element.Footnote ¹⁵

• Aporetic Interpretation. Recently, it has been argued that An. 2.5 does not say anything positive about the passivity of perception whatsoever: it only formulates a dilemma constituted by two different and apparently incompatible descriptions of perception as a kind of being affected by, and assimilated to, the perceptual object on the one hand, and as a non-kinetic activity (ἐνέργεια) on the other.Footnote ¹⁶

I shall argue that none of these approaches can correctly capture the strategic role ascribed to the notion of being affected in An. 2.5. That’s because interpreters have expected both too much and too little from this chapter. On the one hand, they have expected too much when looking for answers to questions about the respective roles of the body and the soul here (Material, Deflationary, and Psychic Interpretation).Footnote ¹⁷ On the other hand, they have expected too little when taking the notion of passivity developed here to be just one horn of a dilemma (Aporetic Interpretation), when taking it to concern only the material side of perception (Material Interpretation), or, again, when deflating this notion to such an extent that nothing genuinely passive remains (Deflationary Interpretation). I shall argue that although An. 2.5 operates at a preliminary stage of inquiry, which makes it impossible to draw any firm conclusion from it about the respective roles of the body and the soul, Aristotle succeeds in outlining here the essence of perception as a specific – namely, complete – kind of passive activity.

To draw out this ground-breaking achievement, I focus on three main issues: (1) Aristotle’s way of distinguishing different kinds of πάσχειν in the core part of An. 2.5; (2) the role played in the whole chapter by the idea that perception is a non-kinetic (i.e. complete) activity; and (3) the way in which Aristotle takes his first general account of perception to surpass his predecessors’ earlier accounts and to solve difficulties inherent in them. In the remaining three sections of the present chapter, the three issues are introduced one by one, with a focus on what is both exegetically and philosophically at stake in each case.

1.2 Passivity and Preservation

At a key juncture of An. 2.5 Aristotle distinguishes between two kinds of πάσχειν:Footnote ¹⁸

There are several interpretative questions about how the kind of πάσχειν that ‘is rather a preservation’ (we can call it ‘preservative πάσχειν’) is introduced here and characterized. To address these worries appropriately, we shall need to analyse not only the sentence but also its larger context (417a21–418a3) in detail in Chapter 3. For now, I only wish to sketch two main existing readings and offer an alternative approach.

The deflationary readingFootnote ¹⁹ is based on interpreting the preposition ὑπό as introducing not the efficient cause (i.e. τὸ ποιοῦν), as one would expect, but the final state to which the πάσχειν in question leads (i.e. the terminus ad quem).Footnote ²⁰ Understandably, the reader who takes this interpretative path then tends to take Aristotle’s point about likeness as saying that the starting point and the end-point of preservative πάσχειν are very much like each other, just as, for instance, the housebuilder who is not active is very much like the housebuilder who is actively housebuilding. The two are separated not by a genuine change, but merely by an innocuous transition.Footnote ²¹ These two interpretative decisions jointly imply that preservative πάσχειν involves, in itself, no genuine passivity whatsoever.

On the other hand, existing non-deflationary readingsFootnote ²² differ in taking ὑπό as introducing the efficient cause and in understanding the point about likeness as spelling out a commonality between the patient and the agent as a condition of the latter acting on the former. Typically, Aristotle is taken to be speaking here about a generic or a potential likeness between the two.Footnote ²³ The upshot of this interpretation is that, except for the term ‘preservation’, everything Aristotle says about the second kind of being affected is a perfectly general description applicable to any πάσχειν whatsoever (as implied by GC 1.7).Footnote ²⁴

Each of these approaches faces exegetical difficulties. The widespread deflationary understanding of ὑπό appears to be very unlikely.Footnote ²⁵ Furthermore, both approaches rely on a very unusual understanding of likeness. Nowhere else in the De Anima does Aristotle mean by ‘likeness’ a likeness of two termini, or a merely potential or generic likeness. One passage in An. 2.5 (416b35–417a2), to be sure, has been widely read as introducing the concept of a generic likeness; but we shall see (in Sections 2.1 and 2.2) that this standard reading faces serious problems. Indeed, throughout An. 2.4–5, and beyond, Aristotle always speaks of ‘likeness’ in terms of a full-fledged likeness between the agent and the patient resulting from πάσχειν, and he always describes the state preceding πάσχειν simply in terms of unlikeness.Footnote ²⁶

More importantly, I shall argue that neither of the two approaches allows us to appreciate the philosophical contribution of the quoted passage to the overall argument of An. 2.5. Under existing non-deflationary readings, the passage fails to specify the notion of preservative πάσχειν in a way that would bring us any closer to understanding what perception is (given that what is said about it holds equally well for any other instance of πάσχειν). Under the deflationary approach, on the other hand, preservative πάσχειν loses any contact with the passivity of perception whatsoever. The troubles implied by this move become evident in Myles Burnyeat’s seminal paper. Burnyeat, who successfully elevated the Deflationary Interpretation to something of a communis opinio, insisted at the same time (rightly I believe) that receptivity of perception is the leading concern of Aristotle’s first general account.Footnote ²⁷ Yet, it is difficult to understand how Aristotle can account for perception’s receptivity after deflating the notion of preservative πάσχειν. Burnyeat’s idea is, roughly, that Aristotle first introduces the notion of preservative πάσχειν at 417b2–5 to capture a mere transition from a second capacity to its fulfilment, and then distinguishes two different kinds of such transitions: those that can and those that cannot be described as ‘alterations of a kind’.Footnote ²⁸ It seems very unlikely, though, that Aristotle wished to undertake this cumbersome conceptual manoeuvre.Footnote ²⁹

I shall argue that, in the quoted passage, Aristotle speaks of a genuine case of being affected and that he describes it in a much more informative way than is presupposed by existing non-deflationary readings. He claims that, in preservative πάσχειν, ‘that which is in capacity’ is both preserved by ‘that which is in fulfilment’ (i.e. the agent) and is assimilated to it. Being affected by – and assimilated to – something else means for the subject here being preserved and, indeed, fulfilled as the sort of thing it is. In other words, it is for the subject exactly what, say, singing a song is for a singer or building a house is for a housebuilder. In this way, the quoted sentence outlines the very essence of perception as a receptive cognitive act.Footnote ³⁰

One important implication is that when the perceiver is affected by, and assimilated to, a perceptual object, her perceptivity is thereby in no way diminished: she can just as easily be affected by and assimilated to any other object or, indeed, the very same one. This is, arguably, how preservative πάσχειν contrasts with its destructive counterpart (such as being heated), which results, instead, in a transition from one state to its contrary and thereby modifies the ways in which the subject can and cannot be affected. When, for instance, a stone has been heated in a sauna from 20°C to 80°C, it is now easier for it to be assimilated to a pot of water at 90°C than it was before, but it is more difficult for it to be assimilated to a pot of cryogenic liquid at –200°C; moreover, it will now be impossible for this stone to be affected by (and assimilated to) the surrounding air at 80°C. When, in contrast, a perceiver has been affected by, and assimilated to, a blue object in the relevant way, it does not thereby become any more difficult for her to be affected by, and assimilated to, a yellow object, or any easier for her to be affected by, and assimilated to, a purple object. Moreover, such a perceiver can also continue being affected by (and assimilated to) the same blue object that she has already perceived. This is the respect in which perceiving is like singing a song or building a house: a builder who is building (or has built) Speusippus’ house becomes thereby – qua builder at least – no less capable of building Aristotle’s house. However, perceiving is not entirely like housebuilding or singing. Unlike these, perceiving consists, essentially, in being affected by, and assimilated to, something else.

The suggestion, therefore, will be that the notion of preservative πάσχειν is intended exactly to draw out this double contrast, and thereby to capture, on the most general level, the essence of perception as a receptive cognitive act. Perception is contrasted both (1) with non-kinetic (complete) activities, like housebuilding, which are productive (or spontaneous) rather than passive, and (2) with passive changes (κινήσεις) as incomplete activities, like being heated. Unlike activities such as housebuilding or singing, perception is essentially passive. However, unlike passive changes such as being heated, perception is a complete, non-kinetic activity. The essence of perception can, then, in the most general terms, be encapsulated in the notion of a complete passive activity, and the primary contribution of An. 2.5 consists exactly in working out this notion. The deflationary reading fails to appreciate (1),Footnote ³¹ while the existing non-deflationary readings fail to appreciate (2).

If this is right, then Aristotle’s account can be understood as incorporating two distinct intuitions about perception, each of which appears to capture something essential about it but both of which prima facie appear to be mutually incompatible – namely, that: (a) perception consists in being affected by, and assimilated to, perceptual objects; and (b) the perceiver must be, and must remain, unlike all perceptual objects and impassive with respect to them in order to remain unbiased and to perceive the object as real and external to herself. These, as we shall see, are effectively the two main competing intuitions that Aristotle identifies in the views of his predecessors.

However, before turning to Aristotle’s predecessors, we must first consider how the notion of completeness is introduced and handled in An. 2.5.

1.3 Passivity, Completeness, and Continued Perceiving

The passage that distinguishes two kinds of πάσχειν belongs to the core part of An. 2.5 (417a21–418a3), where Aristotle draws two sets of distinctions and determines how the notions of being affected and being qualitatively changed are, and are not, to be used with respect to perception. Immediately before Aristotle starts drawing these complex distinctions, he explicitly raises the topic of completeness, while signalling that something about how he is, or will be, handling it here is provisional:

This statement is followed by a formulation of the assimilation model (417a17–21) according to which the patient is unlike the agent insofar as it is being affected (πάσχει) and is like it insofar as it has been affected (πεπονθός). In his seminal paper, Myles Burnyeat drew far-reaching consequences from the quoted passage. He took it as laying down a key methodological constraint that remains in place throughout Aristotle’s treatment of perception. According to Burnyeat, because this inquiry is a part of Aristotle’s ‘physics’, and his ‘physics’ is exclusively about changes (κινήσεις) – that is, incomplete ἐνέργειαιFootnote ³³ – Aristotle invites us ‘to suppose that there is no such thing as complete or unqualified actuality … There is only the incomplete actuality exhibited by a process of change that is defined by and directed towards an end-state outside itself.’Footnote ³⁴ The request is ‘extraordinary’ (as Burnyeat himself describes it) because elsewhere – including An. 3.7 and Sens. 6 – Aristotle is keen to stress that perception is a complete activity.Footnote ³⁵ Indeed, these other passages could easily make one believe that completeness is an essential feature of perception that should in some way figure in any successful account of it. According to Burnyeat, however, such a position is excluded exactly by the fact that physics is limited to considering changes. The worry then becomes whether physics can speak about perception at all. It can, replies Burnyeat, but only if it ‘merges’ ‘the (instantaneous) transition to perceiving and perceiving [itself]’.Footnote ³⁶ On this view, it appears that two errors are expected to cancel each other out. I shall argue, though, that this magic is not needed because neither error is actually committed by Aristotle.

Burnyeat attempts to justify the first error by pointing to Aristotle’s focus on ‘the causality of perception’: this, he contends, can be analysed without taking into account ‘the point that there is no moment of perceiving at which its goal is not achieved’, allowing the latter to be delegated to works other than the De Anima – and, indeed, outside Aristotle’s ‘physics’ altogether.Footnote ³⁷ I shall argue for the exact opposite: the point about completeness of perceiving, which is emphasized in An. 3.7 and Sens. 6, is essential to Aristotle’s analysis of the causality of perception, and already plays a crucial role in the first general account of perception in An. 2.5.

That this is, in fact, the case has not been fully appreciated, I contend, particularly because one question directly relevant for the causality – and indeed the very nature – of perception has not been taken sufficiently seriously. The question can be put straightforwardly: how does the case of continued perceiving differ from the case of merely having an after-image or phantasma of the object I was perceiving a moment ago?Footnote ³⁸ The reason why this question matters to Aristotle is that it represents an instance of a more general issue, which is, arguably, central to his account of perception – namely, that of distinguishing between a case of genuine perceiving and a mere appearance. Moreover, the reason why the question of continued perceiving is so pressing is that it seems particularly difficult for any assimilation model of perception – including the one that Aristotle himself starts to develop in An. 2.5 – to account for the difference of perception from a mere after-image or phantasma. If perceiving X is explained as a way of being affected by, and assimilated to, X, and if the relevant likeness is not something that is progressively achieved through time but rather something that exists from the very first moment of directing one’s senses towards X, then it is not obvious how exactly we should account for the difference between the scenario in which I continue perceiving X and the alternative scenario in which X is already gone but is still appearing to me. Surely, I have a likeness of X in me in both cases; so what is the difference? A related question could be raised for Aristotle’s account of perceptual blind spots:Footnote ³⁹ why is it that perceptual assimilation does not produce such a blind spot? To appreciate the weight of these questions, it is worth noting that continued perceiving is not a special case: all cases of perceiving are eo ipso cases of continued perceiving. This is directly implied by the completeness of perception, and that is one of the reasons why Aristotle can hardly leave this feature out when analysing the causality and the nature of perception. This is an essential feature of perception and one that contains a considerable challenge for the kind of account that Aristotle is developing in the wake of his predecessors.

I shall suggest that this straightforward – but far from simple – question about continued perceiving is present in the background of Aristotle’s concern regarding the traditional view that like is perceived – and is in general known – by like (LKL), and particularly with the implication of this view that in perception like is affected by like (LAL). This is because like being affected by like is exactly what distinguishes continued perceiving from just having an after-image or phantasma (or a blind spot): in both cases, I have a likeness of the object in me, but only in the former case am I also being affected by that object, so that like is affected by like. The problem is that the notion of being affected as developed by Aristotle in GC 1.7 seems a priori to exclude this option, because things that already are like each other, according to this account, can no longer act upon each other. This, I shall argue, is at least a part of the difficulty that motivates Aristotle to draw the distinctions that he does at 417a21ff. These distinctions should help us understand exactly how the assimilation model summed up before this passage (at 417a17–21) and applied to perception at the very end of the chapter (418a3–6) can really work without collapsing cases of continued perceiving into mere appearances.Footnote ⁴⁰

This issue is also to be identified in the background of the quoted passage that signals the provisional nature of Aristotle’s initial discussion at 416b33–417a21 (rather than of his treatment of perception as a whole, as Burnyeat would have it).Footnote ⁴¹ In sharp contrast to Burnyeat’s reading, I submit, it is exactly the observation that perception is not an incomplete activity at 417a16–17 (quoted above)Footnote ⁴² that allows us to understand and appreciate the motivation for and legitimacy of speaking as if being affected and being active were the same thing. The point is that, in an important sense they are, indeed, the same. It would be a non-starter for any account of perception, by Aristotle’s lights, to assume that the perceiver is first being affected by the perceptual object over time interval t₁ before then perceiving it over time interval t₂. If the perceiver is no longer being affected by the perceptual object at the time at which she is perceiving it, how does perceiving differ from just having an after-image of the object? Being affected and being active cannot – in the specific case of perception – be dissociated in any temporal way. Rather, they must be the same at least in terms of their temporal extension.

If this is right, it has an important implication for the ways in which the assimilation model (introduced immediately at 417a17–21) can, as well as the ways in which it cannot, be applied to perception. When Aristotle says – drawing on GC 1.7 – that (1) what is being affected (present tense) is unlike the agent and (2) what has been affected (perfect tense) is like it, (1) and (2) must not, arguably, be contrasted in temporal terms – as they standardly are in other cases of being affected (such as those discussed in GC 1.7) where the completion of being affected by X, and so assimilation to X, excludes the possibility of being further affected by X. Aristotle’s provisional identification of being affected and being active (417a14–17), in other words, brings out what is essential for our correct understanding of the assimilation model (417a17–21) if it is to be successfully applied to perception. In the case of perception, being affected (πάσχειν) passes the tense test together with the activity (ἐνεργεῖν), at least in the sense that having been affected by, and so assimilated to, a perceptual object does not exclude being further affected by that object. This is the key condition needed to account for continued perception. Furthermore, it also turns out to be a key condition of accounting for how an external object can be present to the perceiver – that is, for the fact that rather than turning the perceiver’s organ into a similar perceptual object, the external object makes itself perceived by her.Footnote ⁴³

Under the proposed interpretation (further developed in Sections 2.5 and 2.6), the message of 417a14–17 is, thus, much more positive and constructive than it is usually taken to be. However, Aristotle clearly says that the identification of πάσχειν and ἐνεργεῖν, as introduced here, is only provisional. The identification’s provisional nature, I shall argue, is intended to be overcome exactly by the distinctions that are later drawn at 417a21ff., so that only at the end of the chapter (418a3–6) will the reader be in a position to understand fully how the assimilation model can correctly be applied to perception. With this in mind, we can see that the identification of πάσχειν and ἐνεργεῖν at 417a14–17 is provisional in at least three respects. First and foremost, while the passage – under the suggested reading – indicates that the perceptual πάσχειν passes the tense test, it is far from obvious how this could be the case. In fact, with an understanding of the notion of πάσχειν inherited from GC, it seems impossible for something to have been affected by, and assimilated to, X, and yet still be able to be affected by X. Second, the identification is provisional because the middle term (i.e. change) is a false one. While the identification itself contains an important truth, Aristotle can provide only a preliminary, and strictly speaking false, reason for it, because he has not yet introduced the appropriate notion of being affected as independent from the notion of change. Finally, the identification is also provisional because, while being affected and being active have, apparently, the same temporal extension in the case of perception, they are not strictly speaking the same. Rather, while they are numerically the same, their being differs, and Aristotle owes us an account of this difference.

We shall see (in Sections 3.2 and 3.5) that the distinctions given in 417a21ff., and the notion of preservative πάσχειν in particular, help Aristotle overcome these deficiencies. Rather than introducing an inadequate merging between the transition to perceiving and perceiving itself, Aristotle explains at 417b2–12 just how perceiving as a complete activity can also be a passive one.

1.4 Aristotle’s Interlocutors

The proposed interpretation therefore provides a fresh perspective on Aristotle’s concern with the view – present throughout An. 2.5 – that, in perception, like is affected by like (LAL). Standardly, interpreters take LAL to be true for Aristotle insofar as it points to the condition of generic likeness.Footnote ⁴⁴ Yet, that has nothing to do, specifically, with perception. Accordingly, on such a reading it is difficult to understand why Aristotle makes the question of the truth and falsity of LAL central to his argument in An. 2.5. Indeed, on such a reading, it turns out that the notion of preservative πάσχειν can hardly contribute anything to our understanding of LAL. However, if this is the case, the closing lines (418a3–6) appear to be just a dull repetition of the assimilation model from 417a17–21. If, in contrast, the truth of LAL is understood along the lines sketched out in the preceding section, it captures a non-trivial insight into the very essence of perception as a receptive cognitive act and we can easily understand how the distinctions presented in 417a21ff. are needed to secure this insight. Moreover, under this interpretation we can better appreciate Aristotle’s engagement with the anonymous thinkers to which LAL is ascribed at 416b35–417a2. There is little doubt that these are (some of) the proponents of the traditional view that like is known by like (LKL). Yet, the connection Aristotle sees between LKL and LAL merits further investigation.

This question opens up the larger issue of how Aristotle’s presentation of his first general account of perception in An. 2.5 draws on – and responds to – the critical discussion of his predecessors in Book 1. The importance of this question for the interpretation of An. 2.5 was already emphasized by Burnyeat in his seminal paper.Footnote ⁴⁵ However, Burnyeat’s understanding was framed by the influential idea, promoted in the 1960s by G. E. L. Owen and Suzanne Mansion, according to which Aristotle’s search for principles is a dialectical undertaking starting from ‘reputable opinions’ (ἔνδοξα) as the relevant kind of ‘what appears to be the case’ (φαινόμενα).Footnote ⁴⁶ This idea has recently come under attack,Footnote ⁴⁷ and, with respect to the De Anima specifically, it has been emphasized just how sharply Aristotle’s dealings with his predecessors differ from a purely dialectical procedure.Footnote ⁴⁸ Jason Carter has offered an analysis of Aristotle’s concern with his predecessors in An. 2.5 based on safer methodological grounds and on a meticulous reconstruction of Aristotle’s argumentation in Book 1.Footnote ⁴⁹ Carter has shown that, throughout the De Anima, while developing his own view, Aristotle is deeply engaged in a discussion with his predecessors and that understanding this engagement can be a great help in reconstructing Aristotle’s own position – without this taking anything away from the scientific rigour of Aristotle’s thought.Footnote ⁵⁰

I shall argue in Chapter 2 that a yet more nuanced picture of Aristotle’s engagement with his predecessors is needed in the specific case of An. 2.5. I take it that what has not been sufficiently appreciated here is the deeply aporetic nature of this engagement. One of my central contentions will be that, while Aristotle explicitly refers in An. 2.5 only to LKL (or, more precisely, to its LAL implication), he is effectively addressing it together with another view, since LKL represents one of two horns of the key puzzle that Aristotle is dedicated to resolving in Book 2. Given that LKL is relevant for him exactly as being productive of one horn of a problem that he thinks his own theory must be capable of resolving – namely, a problem with explaining perception – he could not properly address LKL without also responding, albeit implicitly, to the view that is productive of the other horn of that problem. This other view, I shall argue, is Anaxagoras’ idea that what knows X needs to be neutral and impassive with respect to X. Taken together, the two views articulate exactly the two, seemingly incompatible, intuitions that are to be incorporated into Aristotle’s own notion of preservative πάσχειν (as suggested in Section 1.2). Roughly, they say that (a) in order to know something, one needs to be affected by it as like by like, and that (b) in order to know something, one needs to be neutral and impassive with respect to it, and the object must remain external.

It helps to bear in mind, in this connection, what Aristotle says about the importance of puzzles (ἀπορίαι) for scientific inquiry and the role that one’s predecessors play in formulating and helping one navigate such puzzles. The discussion of Aristotle’s predecessors in An. 1 is not motivated by a detached historical interest in what people were thinking in the past, or by a triumphalist urge to show that everyone before him was wrong. In fact, An. 1.2 contains one of Aristotle’s clearest statements of what he takes himself to be doing when engaging with the thoughts of those who came before him:

The necessary first step in discovering the account of the soul as the first principle of embodied life, as in any such endeavour, is to identify the problems that impede us from arriving at a full understanding of the soul – the central questions that our account is supposed to answer and the key puzzles that it is supposed to resolve.Footnote ⁵¹ A helpful way of identifying these key puzzles, Aristotle believes, is critically reviewing the opinions of those who already made serious attempts at providing some such account in the past. In the most prominent views developed by one’s predecessors over the course of centuries, and in the arguments that have been provided in their defence, it is likely that at least the proverbial grain of truth has been crystalized – although these views tend to contradict each other and their respective ‘truths’ often seem mutually incompatible. In another methodological reflection (at GC 1.7, 323b17–18), Aristotle provides a succinct analysis of the usual situation: the conflicts arise because ‘where one needs to grasp a whole (δέον ὅλον τι θεωρῆσαι), each of the sides happens to capture only a certain part (μέρος τι τυγχάνουσι λέγοντες)’.Footnote ⁵²

Aristotle’s goal, then, is to preserve what is true (and genuinely well-argued) in each of his predecessors’ relevant views (τὰ καλῶς εἰρημένα λαβεῖν) and to prevent himself from falling into the difficulties that the proponents of these views were getting into (τὰ μὴ καλῶς εὐλαβηθῆναι) – whether they were themselves aware of it or not. The project, in other words, is to provide a resolution, showing how the respective truths of conflicting (and often fallacious) theories can be combined into a single coherent account that finally manages to ‘grasp the whole’. It would be a caricature of Aristotle’s procedure if we imagined that the goal could be achieved on purely dialectical grounds or, say, by simply listing all the relevant claims of one’s predecessors and discarding the false ones. The hope is rather that a serious engagement with our predecessors will allow us to identify the key problems that must be dealt with and solved in order to develop a successful account. But the solution cannot, of course, be found by further thinking about one’s predecessors and what they said. Rather, the solutions can be found only by inquiring deeper into the matter itself than one’s predecessors did. The fact that this inquiry, if successful, will finally make us capable of showing how the truth of each side can be taken on board while overcoming the errors and the apparent incompatibilities of our predecessors’ views only means that our account passes a very useful test that critical discussion of our predecessors provided. One reason why such a test is useful is that it allows one seriously to claim that significant progress has been achieved.

In An. 1, Aristotle identifies two main issues concerning the soul that his predecessors had been interested in addressing: (a) how the soul can be what makes animals capable of perception and of knowing in general, and (b) how the soul can be what makes animals capable of self-motion.Footnote ⁵³ The main stretch of An. 1.2 (404b7–405b30) and most of An. 1.5 (409b23–411a26) is dedicated to the first of these issues. Aristotle’s analysis of this question, I contend, can be subsumed as a whole under one central puzzle formulated towards the end of An. 1.2 (at 405b12–23).Footnote ⁵⁴ Aristotle identifies here two main views on the nature of knowing, which directly bear on how the soul, as the first principle of knowledge, should be conceived. Each of these views appears to be well justified, but they seem to contradict one another and each of them leads to apparently unsolvable difficulties. To summarize the situation very roughly: one of the two sides (the majority view) says that the subject knows the object on account of being like it (LKL) and being affected by it (LAL); the opposing side (Anaxagoras) says that the subject knows the object on account of being unlike it and impassive (ἀπαθές) with respect to it. The former looks attractive because, in order to know something, it seems necessary that one have some kind of likeness of it within oneself and that one be continuously in touch with it (call this the Acquaintance/Contact Requirement). The latter looks attractive because, in order to know something, it also seems necessary to remain neutral and unbiased with respect to it and to other potential objects of knowing, and it seems necessary that the object remain external and untainted (call this the Unbiasedness/Externality Requirement).

If Aristotle believes that each of these views contains an important true insight, what is the way out of the puzzle? So far, Aristotle’s account of perception has not been explored from the perspective of this question.Footnote ⁵⁵ And yet, it is not just Aristotle’s explicit reflection on the use of puzzles (quoted above) that suggests he is willing – and believes it is important – to give an answer to this question. There is, additionally, a passage in Theophrastus’ De Sensibus 19 suggesting, as we shall see (in Section 2.7), that, in Aristotle’s school, any satisfactory account of perception was expected to explain how the truth of LKL (and LAL) can be combined with the truth of the view that the perceiver needs to be impassive with respect to her object.

In Chapter 2, I show, step by step, how the key puzzle from An. 1.2 brings us to a deeper understanding of Aristotle’s first general account of perception and how it sheds light on the notion of preservative πάσχειν in particular. It is this background that will also help us understand Aristotle’s implicit inference (at An. 3.4, 429a13–16) from the passivity of perception to an impassivity on the part of the perceiver.