Nous in Aristotle's De Anima Caleb Cohoe Abstract: I lay out and examine two sharply conflicting interpretations of Aristotle's claims about nous in the De Anima (DA). On the human separability approach, Aristotle is taken to have identified reasons for thinking that the intellect can, in some way, exist on its own. On the naturalist approach, the soul, including intellectual soul, is inseparable from the body of which it is the form. I discuss how proponents of each approach deal with the key texts from the DA, focusing on four of the most important and interesting topics in this area. Two of these topics concern the activity of understanding (noêsis): first, what does Aristotle mean when he claims that the intellect cannot have a bodily organ and, secondly, what role does Aristotle think phantasmata ("images" or "representatations") play in understanding something? Two of the topics concern DA 3.5, one of the most difficult passages in Aristotle's corpus: first, what is the nature and role of the productive intellect (nous poiêtikos) introduced there and, secondly, what are this chapter's implications for the question of whether the intellect or intellectual soul can exist apart from the body? I conclude by identifying areas where further research is necessary. 1. Introduction Claims about nous ("intellect") are central to Aristotle's overall account of the nature of living things, as expressed in his De Anima (DA) or On the Soul, and to the culmination of his account of reality as presented in Metaphysics Λ. Yet over the past thirty years, nous has been relatively neglected in discussion of the DA. Recently, however, interpreters have begun to recognize the importance of Aristotle's account of the intellect and its activities for understanding his account of cognition, his overall conception of living things, and his views on the place of human beings in the universe. In this article, I will lay out the main current interpretative disputes concerning Aristotle's claims about nous in the DA, examine some of their broader implications, and identify areas where further research remains to be done. Aristotle is well known for defining the soul in relation to the body, characterizing it as "the first actuality of an organic body." (DA 2.1, 412b5–6) The soul is the principle Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 2 that makes the bodies of living things actually be alive. Aristotle's approach to the soul is often contrasted with Platonist views of the soul that emphasize its separability from the body. The case of nous, the intellect or power of understanding, presents some complications to this picture. Aristotle asks at the beginning of the DA, but postpones answering, whether some kinds of soul might be separable from the body. He presents a separability condition: a soul is separable from the body if it has some activity that can be done without the body, with the activity of understanding being the most plausible candidate (1.1, 403a8-16). Aristotle later argues in DA 3.4 that, in fact, the activity of understanding has no bodily organ, suggesting it may be able to be done without the body. Further, in DA 3.5 he maintains that there is a kind of intellect that is undying and everlasting, again suggesting the possibility that some sort of understanding is separable from the body. On the other hand, he maintains in DA 3.7 and 3.8 and De Memoria 1 that the activity of understanding makes uses of phantasmata ("images" or "representations") which are themselves produced by a bodily organ. This suggests that understanding may, in fact, require the body, with the result that even intellectual soul would be inseparable from the body. This diversity of texts together with Aristotle's failure to provide us with a fully worked out, detailed and comprehensive answer to the separability question has led to a diversity of interpretations. This article will examine two sharply conflicting ways in which scholars have made Aristotle's claims about nous cohere with his general views on the nature of soul.1 On the first approach, which I will call the human separability 1 Some 19th and 20th century scholars advocated for a developmental approach to these texts, maintaining that Aristotle's claims about nous conflicted with Aristotle's general hylomorphic characterization of the soul and thus belonged to a different phase of his development (e.g. Jaeger 1934, 332-4; Ross, "The Development of Aristotle's Thought", 65-7). This approach has few contemporary Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 3 approach, Aristotle is taken to have identified reasons for thinking that the activity of understanding does not employ the body and thus that the intellect can, in some way, exist on its own. This interpretative approach has a number of distinguished historical proponents, including Thomas Aquinas, as well as several contemporary scholars who advocate versions of this approach, such as Lloyd Gerson and Howard Robinson. The second approach, which I will call the naturalist approach, understands Aristotle's account of the soul to be fully within the bounds of natural philosophy. On this account, the soul's status as the form of the body is the same as the status of any other natural form, such as the form of fire or the form of gold. The soul, including intellectual soul, is inseparable from the body of which it is the form, just as the form of fire and the form of gold are, for Aristotle, inseparable from fire and gold. Interpreters adopting this approach either minimize the force and extent of Aristotle's claims about the divine and separable nature of the intellect or take these claims to refer not to the intellects of human beings or other natural creatures, but to the divine intellect of Metaphysics Λ. This approach has seen a resurgence in the last two decades (e.g. Wedin; Frede, "On Aristotle's Conception of Soul;" Caston, "Aristotle's Two Intellects: A Modest Proposal;" Burnyeat). It also has ancient and medieval antecedents going back at least to Alexander of Aphrodisias.2 I will discuss how proponents of each approach deal with the key texts from the DA and summarize the resulting views, identifying their key strengths and challenges, defenders. There is little textual or testimonial evidence for supposing the texts concerning nous to be from a different work or a different period. Indeed, Theophrastus, Aristotle's pupil and successor, treats Aristotle's discussion of intellect in DA 3.5 as a given part of Aristotle's psychology (Themistius, 108.228). There is also evidence of continuing revision in some of Aristotle's texts, providing some reason for thinking that the text of the DA would not retain views that Aristotle himself came to reject. Given these facts, the developmental hypothesis has found little favor in recent scholarship. 2 Franz Brentano offers a general survey of ancient and medieval views on the status of the nous poiêtikos of DA 3.5 (Brentano, 313-342). 3 For further discussion of this model and its application see Cohoe, 350-357 and Lorenz. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 4 both interpretative and philosophical. My discussion will focus on four of the most important and interesting topics in this area. Two of these topics concern the activity of understanding (noêsis): first, what does Aristotle mean when he claims that the intellect cannot have a bodily organ and, secondly, what role does Aristotle think phantasmata ("images" or "representatations") play in understanding something? Two of the topics concern DA 3.5, one of the most difficult passages in Aristotle's corpus: first, what is the nature and role of the productive intellect (nous poiêtikos) introduced there and, secondly, what are this chapter's implications for the question of whether the intellect or intellectual soul can exist apart from the body? I will conclude by identifying areas where further research and debate are necessary. 2. The Intellect and its Lack of a Bodily Organ In DA 3.4 Aristotle begins his discussion of the intellect, "the part of the soul by which the soul knows and judges," (429a10-11) by applying the model of cognitive change that he introduced in DA 2.5: the intellectual power must be receptive of intelligible forms and potentially like them, just as, in DA 2.5, the perceptive power was receptive of perceptual forms and potentially like them. Just as the eye is receptive of the forms of color it enables us to see, so the intellect must be receptive of the forms of the objects it enables us to understand, such as color or horse or triangle.3 After applying this model, Aristotle claims that the intellect is not mixed with the body (amigês) and is unaffected (apathês) by it, since mixture with the body would inhibit the intellect's ability to understand all things (429a18-b3). While the power of perception is "not without body," the intellect is "separable" (chôristos). (429b3-5) What do these claims mean and why does Aristotle endorse them? I will discuss some of the 3 For further discussion of this model and its application see Cohoe, 350-357 and Lorenz. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 5 more important recent attempts to understand Aristotle's reasoning (recent literature includes Shields, "Intentionality and Isomorphism in Aristotle"; Caston, "Aristotle's Argument for Why the Understanding is not Compounded with the Body"; Sisko, "On Separating the Intellect from the Body: Aristotle's De Anima III.4, 429a20-b5"; Polansky, 434-445; Cohoe). The strong claims Aristotle makes here raise problems for naturalistic interpretations, since Aristotle looks to be maintaining that the intellect can operate, and perhaps even exist, apart from the body. One naturalist strategy has been to maintain that Aristotle is only claiming that the intellect has no specific bodily organ. As Victor Caston puts it, Aristotle's conclusion "need mean no more than this: that there is no organ of understanding, that is, no discrete part of the body that is dedicated to its functioning, as there is for each of the other capacities that make up the soul." (Caston, "Phantasia and Thought" 329) Both Caston and Michael Wedin defend this strategy, claiming that despite appearances, Aristotle thinks the activity of understanding does, in fact, employ the body.4 This interpretation, however, seems to implausibly underplay the force of Aristotle's claim that the intellect must be unmixed with the body. In De Sensu 7 and DA 3.2 Aristotle discusses common perception, an ability that involves being able to unify and compare sense-perceptions from different sense modalities. Although common perception relies on the various distinct bodily organs of the different sense-modalities (449a9-10), Aristotle does nothing to suggest that common perception's use of a number of distinct bodily organs makes the resulting activity immaterial or non-bodily. Thus it 4 Their views are based on the role they believe phantasmata or representations play in understanding, a topic I will turn to in the next section Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 6 seems doubtful that he would describe the intellect as separate from the body just because it used various parts of the body instead of confining its activity to one area. Other interpreters have simply dismissed Aristotle's assertions in this passage, claiming that we should ignore them since they are based on faulty reasoning or defective empirical observation (e.g. Kahn; Sisko, "On Separating the Intellect from the Body" 253, 264-6). Even if Aristotle's reasons are flawed, the fact that he makes such assertions is still important if we are trying to understand what his account of the intellect and the soul actually is. Further, Aristotle's arguments may be more cogent than his critics have recognized. Cohoe has recently argued that Aristotle has reasons for claiming that no physical structure could enable a bodily part or combination of bodily parts to act as an organ of understanding. He draws attention to Aristotle's claims that in understanding something we grasp its essential features, features that apply to all its instances. Cohoe claims that Aristotle holds that cognition that operates through bodily organs, as perception does, can only allow us to cognize particular, spatiotemporally individuated, instances of a thing. Since understanding, by contrast, is characterized by its universality, it cannot operate through a bodily organ (Cohoe, 372-375). This reading suggests that we should take Aristotle's strong claims about the separability of nous from body seriously. If Aristotle is endorsing such claims, do they raise problems for the coherence of his views? Does thinking that the intellect is separate from the body endanger Aristotle's conception of the soul as the form of the body? The answer to this question depends on how we understand Aristotle's account of the soul and its relation to the body. It is, however, worth noting that at several points in the DA Aristotle explicitly raises the Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 7 possibility that the intellect is separable from the body in a way that other powers of the soul are not.5 He does not rule out this possibility on grounds of incoherence or incompatibility. Scholars who interpret Aristotle as a sort of functionalist, someone who takes the soul to be an aspect of the body or a special way of describing the abilities that certain bodies possess, tend to think that Aristotle's view of the soul-body relation precludes the possibility of separation (e.g.. Barnes, "Aristotle's Concept of Mind" 33 and Aristotle: A Very Short Introduction 107; Kenny; Granger; Guthrie, 284; and Frede, "On Aristotle's Conception of Soul" 98). Recently, however, this sort of interpretation of Aristotle has been challenged, with scholars pointing out that, for Aristotle, the soul as form has a clear explanatory and ontological priority over the body, both in explaining living activities and in determining what kind of body is necessary for them (Shields, "The Priority of Soul in Aristotle's De Anima: Mistaking Categories?" and Menn). On this more muscular view of the soul, the possibility of the soul having an aspect that does not require the body seems less improbable. Debate in this area continues, however, with no immediate resolution in sight.6 3. Understanding and Phantasmata 5 After giving his general definition of the soul, Aristotle explicitly brings up the possibility of an exception or complication in the case of some aspect of the soul, (DA 2.1, 413a3-7) and later notes that nous seems to be of a different kind from the other soul powers (2.2, 413b24-29.). C.f. DA 1.1 403a10-12; Metaphysics Λ 3, 1070a21-26. 6 For further discussion of the issues involved in the relationship between nous and Aristotle's conception of soul and body see Modrak. Here, as elsewhere on this topic, issues arise concerning the direction of interpretation and explanation. Should we first determine whether Aristotle's general account of soul and body is compatible with souls existing apart from bodies and then examine his comments on nous in that light or should we first determine whether Aristotle's claims about nous commit him to the possibility of souls existing apart from bodies and then interpret his understanding of the soul on that basis? The best mode of interpretation would seem to involve taking all the texts into account, so that before giving a verdict we carefully consider both his general claims about soul and his specific claims about nous, but determining the appropriate weights of the various texts and narrowing the interpretative options is quite difficult, as commentators over the centuries have found. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 8 Even if, however, naturalist interpreters ultimately concede that for Aristotle the intellect does not have a bodily organ at all, there is still another line of defense for their interpretation. At several points, Aristotle claims that the activity of understanding employs phantasmata, images or representations that are produced by phantasia, the power of imagination or representation, a power that does employ bodily organs (DA 3.7, 431a14-17, 431b2; 3.8, 432a3-14; De Memoria 1, 449b30-450a9). Wedin and Caston have used the connection between understanding and phantasmata to argue that intellectual activity is still bodily, since Aristotle claims at the beginning of the DA that if understanding "either is a kind of phantasia or not without phantasia, it will not be possible for this to exist without the body." (403a8-10) Given that he seems to affirm this second option in these later passages, there appears to be good reason to agree with the naturalist interpretation and thus to reject the human separability interpretation. The force of this evidence is, however, somewhat mitigated by two considerations. First of all, Aristotle never discusses the connection between understanding and phantasmata in the context of evaluating whether the intellect or its activity are separable from the body. Secondly, the passages in the DA that posit a connection between the two occur in specific contexts that limit their scope, occurring either in the context of practical understanding (as in DA 3.7, 431a14-17 and 431b2) or where the objects of cognition being considered are all inseparable from perceptible magnitudes (as in DA 3.8 432a3-14).7 Aristotle himself suggests that exercising 7 DA 3.8 operates on the assumption that there is no pragma (thing) separated from perceptual magnitudes. Aristotle typically uses pragma to refer to concrete, composite things as Polansky notes (Polansky 495, fn. 3) and so the passage's scope seems restricted to perceptible things and abstractions from perceptible things, as Aristotle's comments at 432a5-6 suggest. The connection posited by De Memoria 1, 449b30-450a9 seems to be more general, though Aristotle does little there to indicate why such a connection would hold universally, if, in fact, he thinks it does. As Samuel Baker has pointed out to me, it may be a "for the most part" claim, like many of the claims of Aristotle's natural philosophy. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 9 understanding concerning perceptibles is more difficult than exercising understanding of non-perceptible objects (DA 2.5, 417b22-28). This leads some, such as Thomas Johansen, to suggest that the connection between understanding and phantasmata may only apply to our understanding of perceptible things (Johansen, 236-7 and 240). Given that Aristotle believes we can understand some things that are entirely non-perceptible, such as the first mover or divine being of Metaphysics Λ, Aristotle may still hold that some activities of understanding do not require the body at all. The connection between phantasmata and understanding may only apply for the most part, in which case at least some activities of understanding would not employ the body at all. Nevertheless, the fact that Aristotle seems to think that the use of phantasmata is often, and perhaps always, a precondition for the exercise of understanding does raise difficulties for the human separability view. 4. The Intellects of De Anima 3.5 Before considering the overall merits of the two interpretative families, we need to consider the last and most difficult text: DA 3.5.8 This chapter of the DA is famously challenging, as numerous scholars have noted.9 Commentators have offered opposing views concerning both the meaning of the text and the text's relation to the larger project of the DA. I will start with a brief summary of the key claims Aristotle makes in the chapter, trying to be as neutral as possible while pointing out some of the many ambiguities in the text. 8 There are a few other texts on nous earlier in the DA that are relevant to some of the issues considered in this article, particularly 1.4, 408b18-31, but space precludes me from giving their interpretation careful consideration, particularly given that the passage in 1.4 is from the aporetic section of the work, making it difficult to determine to what extent the views being discussed there are Aristotle's own. 9 Theiler claims that "there is no passage of ancient philosophy that has provoked such a multitude of interpretations as this half-page chapter. Its obscurity and extreme brevity are notorious" (142); quoted in Shields, "The Active Mind of De Anima iii 5." Along similar lines, Blumenthal notes that the passage "has caused more controversy than any other single chapter of Aristotle," (152) and Johansen describes it as "amongst the most obscure and contested in the corpus." (237) Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 10 The chapter opens with Aristotle arguing that there must be a productive intellect in the soul (or, perhaps, in the case of soul), as well as a receptive intellect, drawing on a broader claim about the general need in nature for two factors: one that is receptive and serves as matter and one that is the cause or the maker (poiêtikos). He makes an analogy between the role of this productive intellect in producing understanding and the role of light in making colors actual. Aristotle then characterizes this productive intellect as separable, unaffected, and unmixed, while also being actual in its essence or substance (chôristos kai apathês kai amigês, tê(i) ousia(i) energeia). He claims that "when separated, this alone is undying and everlasting (athanaton kai aidion)." (430a17-18)10 Aristotle states that "we do not remember, because this is unaffected (apathês), but passible (pathêtos) nous is corruptible (phthartos)." (430a24-5) He concludes by claiming that "without this nothing thinks" (where this can be taken as referring to either of these two sorts of nous), or, alternatively, "without this, it thinks nothing" (where the antecedents to both it and this would be ambiguous). As my summary shows, even coming up with a generally agreed upon translation of this chapter is extremely difficult.11 Given the extremely compressed nature of this passage and the lack of a parallel discussion of the relation between these kinds of nous elsewhere, it is no surprise that there has been persistent disagreement about how to interpret this chapter. I will present three of the main interpretations of this chapter, outlining their strengths and weaknesses and noting how they relate to the naturalist and 10 The antecedent of this is most often taken to be the productive intellect, but some interpreters have argued that the antecedent is knowledge (epistêmê) itself (e.g. Polansky 465-467) or the whole intellect (e.g. Aquinas, Lectio 10). 11 Aristotle leaves the subject of the verb unexpressed at several points, with several different grammatically and linguistically possible candidates. He does not fully define the kinds of nous he discusses, relying on analogies to specify the role of productive nous. He also fails to explicitly correlate the kinds of nous discussed here with those mentioned elsewhere in the work or in the corpus. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 11 human separability views. There are two main overall questions about this chapter: first of all, what is the nature and role of the productive intellect (nous poiêtikos) introduced in this chapter? Secondly, what are the implications of this chapter for the question of whether the intellect or intellectual soul can exist apart from the body? Over the last twenty years, a number of scholars have answered this first question by maintaining that the productive intellect is not a human intellect, but is instead the divine intellect of Metaphysics Λ (e.g. Frede, "La theorie aristotelicienne de l'intellect agent"; Caston, "Aristotle's Two Intellects: A Modest Proposal", and Burnyeat). On this view, the productive intellect makes things intelligible by being the first intelligible, giving structure and intelligibility to the entire universe. Several of these scholars have argued that the productive intellect is not important to Aristotle's psychology as such. Burnyeat has maintained that this passage is an "excursion into theology:" the chapter is "wholly focused on God," not the human intellect (Burnyeat 39). Caston has argued for a similar interpretation, maintaining that the productive intellect is to be understood not as an efficient cause, but as a final cause or background condition. It is because there is a divine intellect that there are intelligible things. This is all that Aristotle's claims about the productive intellect mean. The productive intellect does not play any particular causal role in individual episodes of human thinking (Caston, "Aristotle's Two Intellects: A Modest Proposal"). There are several reasons to question the claim that DA 3.5 is primarily about theology. First of all, Aristotle is usually very careful about distinguishing between claims that belong to first philosophy and those that belong to some other science.12 An unacknowledged jump into a different sort of theoretical inquiry would be rather 12 See, for instance, his discussion of the arguments of Parmenides and Melissus in Physics 1.2. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 12 surprising.13 Secondly, the fact that Aristotle claims that both productive and receptive nous are found "in the soul" (en tê(i) psuchê(i)) suggests that productive nous can be found in the individual soul.14 Finally, the interpretations of Burnyeat and Caston require taking the divine intellect to be one kind of soul, since they take productive nous to be a kind of soul. Aristotle, however, never ascribes soul to living beings such as the unmoved mover, beings that are wholly non-bodily and without any potentiality, calling into question whether he would be willing to describe the divine nous as a soul. Michael Frede avoids some of these difficulties while still offering an interpretation on which productive nous is divine nous. On his account, the divine nous is an efficient cause of understanding for every object we come to understand, making 3.5 an important part of Aristotle's psychology. Frede thinks that Aristotle's divine being is both the source of all intelligibility and the ultimate object of understanding.15 To understand anything, we need to understand it as part of the system of concepts, a system 13 Indeed, there are indications that Aristotle is being careful to address only the questions necessary for this particular inquiry. Aristotle ends DA 3.7 by postponing discussion of whether intellect, while not being separated from magnitude itself, can understand things that are separated. The DA does not attempt to answer every question about thought and its objects. Instead Aristotle is giving an account of what the basic intellectual activities and powers of the soul are. DA 3.7's postponement of discussion about our ability to understand separated things would be particularly odd, if his discussion in 3.5 argues or assumes that any understanding of things is dependent on understanding the separated divine substance 14 Burnyeat and Caston offer a taxonomic reading of Aristotle's usage here. Caston claims that, "[t]he opening clause states that a certain distinction can be found in any kind or type...found in nature." (Caston, "Aristotle's Two Intellects: A Modest Proposal" 206) On his reading, Aristotle takes a general claim about every natural kind and then applies it to psychological kinds. The problem with this reading is that it leaves Aristotle with a highly implausible general claim: that in every sort of natural kind there is both an active species of that kind and a passive species of that kind. There must, for instance, be both an active species of zebra and a passive species of zebra, as Michael Pakaluk has pointed out (Pakaluk 204). Further, the comments of Theophrastus, Aristotle's pupil, seem to indicate that he took Aristotle to be speaking of differences found in the individual soul (Themistius, 108.22-8). 15 Frede, "La theorie aristotelicienne de l'intellect agent" 386-390. Frede does claim that the divine intellect explains the general possibility of knowledge and understanding rather than explaining why I currently understand the forms that I do, but this is because of his general views on what efficient causes are for Aristotle, not because he thinks the divine intellect fails to count as an efficient cause (379-380). Caston himself concedes that the divine intellect counts as an efficient cause for Aristotle, but maintains that it is not part of "what we would call the causal mechanisms of thought" (Caston, "Phantasia and Thought" 332). Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 13 that leads back to god, the first principle of everything. Frede takes Aristotle's god to be the same as the integrated system of essences.16 He makes use of Aristotle's claim that the activity of the agent is present in the patient to explain the way in which god comes to be in my soul (Physics 2.3; cf. DA 3.2 425b26-426a15). God is the agent when I understand something and thus god comes to be in my soul for as long as I am exercising this understanding. This is the divine, productive nous that comes to be in me for a time but is separated from my corruptible nous when I die. Interpretations that take the productive intellect to be god have certain strengths. They clearly specify how and why the divine intellect is separated from the intellect that is subject to corruption. They also clearly resolve the question of separability, denying any human separability and endorsing a naturalistic view. However they face the challenge of explaining why we should think that, for Aristotle, the sort of understanding (noêsis) human beings perform is identical to the divine understanding. While the idea of god as a system of essences is certainly present in late Platonism, it is not clear that Aristotle himself contemplates or endorses such an idea in Metaphysics Λ or anywhere else.17 Indeed, Aristotle seems dubious of the idea that our human minds could ever fully rise to the divine understanding (Cf. Λ 8, 1072a24-30). Proponents of such interpretations need to do more to explain how a human activity that is the fulfillment of a power and that can only take place for a limited time could ever be the same as the entirely simple and timeless activity that Aristotle's god is. Even if Aristotle thinks humans can achieve an act of understanding identical to god's understanding, he may not take the understanding (noêsis) at issue in 3.4-5 to be 16 Similarly, Burnyeat has maintained that the divine being and the correct system of concepts are the same (Burnyeat, 40-43). Burnyeat's view has affinities to that of Frede as well as that of Caston. 17 Cf. Plotinus, V 9 [5], 5-9. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 14 this highest theoretical understanding, a completed understanding of the essences of things which few of us can ever achieve.18 In DA 3.6 Aristotle goes on to claim that nous is the power responsible for combining notions (noêmata) on the basis of the understanding (noêsis) of indivisibles it has already achieved. Aristotle explicitly allows for error when nous produces such combinations (DA 3.6, 430a26-430b2, 430b27-31). This suggests that he is speaking of the sorts of intellectual achievement open to reasonably intelligent and educated human beings, not just the completed scientific knowledge available only to the wisest after long years of arduous study. His example of the combination of notions, thinking that the diagonal of a square is incommensurable with its sides, is a good instance of an intellectual activity that involves some grasp of an essence and some degree of knowledge, but need not involve completed knowledge of geometry.19 In DA 3.6-7 Aristotle seems to be building on the account of understanding that he has given in 3.4-5 in order to give an explanation of different, more complex intellectual activities, including those that sometimes involve mistakes and errors.20 Thus there are some reasons to doubt this first, naturalistic interpretation. 18 This is the position of Burnyeat, 24-8, 35-6; cf. Frede, "La theorie aristotelicienne de l'intellect agent" 388-390. Burnyeat explicitly separates off understanding from ordinary human intellectual activities and claims that Aristotle is not interested in explaining such activities. Frede is less clear. He claims that Aristotle is saying we need to know God as first intelligible to understand anything, but whether Frede thinks this holds true for all our thinking or just the special high-level thinking that is understanding is unclear to me. At least some of Frede's claims suggest that Aristotle is not trying to explain our ordinary thinking, but our highest intellectual understanding of things. 19 DA, 3.6, 430a30-3. To truly see that the diagonal of a square is incommensurable is certainly a significant intellectual achievement, but it does not require a completed and perfected understanding of either what a square is or what it is to be incommensurable, much less a perfected understanding of all essences in light of the divine intellect. Indeed, one could possess some understanding of incommensurability without being able to specify in every case whether two geometrical entities are commensurable or not. 20 The structure of Aristotle's treatment of intellectual activities, in which he begins with understanding (noêsis), the simplest and most basic intellectual activity and the one most proper to intellect, seems to parallel his treatment of perception which focuses on the proper objects of perception (such as color, sound, and smell), which are simplest and most proper to their senses. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 15 Lloyd Gerson offers a second sort of interpretation that allows for a kind of human separability. On his view, there are two sorts of human intellectual activity. There is first of all the ongoing and unchanging activity of (human) "intellect itself." (Gerson, 356) This intellect is a separate subject that unceasingly understands everything: it is not a part of the human soul or the composite human being. (Ibid., 371) Nevertheless, it is not the same as the divine intellect because there is still in it a distinction between potentiality and activity and because it is essentially related to human thought. Secondly, there is the intermittent intellectual activity of composite human beings, the intellect "as it exists in the composite individual." (Ibid., 356) This comes about as a result of our access to and use of intellect itself, but this activity belongs to us and to our souls, not to intellect itself. On Gerson's account, in DA 3.5 Aristotle is explaining how we come to be connected to intellect itself. Intellect enters into us and produces the "passive intellect," the intellect that is part of our soul and that we think with as composite beings. Gerson's interpretation of 3.5 provides an account that fits the chapter into the broader context and makes the productive intellect a central and important part of Aristotle's account of intellectual activities. Gerson's view also offers a clear position on the question of separability: individual composite human beings and our souls are not separable, but human intellect itself exists eternally in separation from any human body. However, his interpretation faces several difficulties. To begin with, it relies on the idea that different human activities have different subjects: sometimes my body is the subject, sometimes the whole composite, sometimes my soul, sometimes my intellect. Gerson argues that I can identify with any of these aspects but that I am "ideally" the same as intellect itself. (Gerson, 366-7) This commits Gerson to denying a plausible and widely Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 16 held view: that, for Aristotle, the composite human being is the proper subject of all human activities, in virtue of the soul and its powers (cf. DA 1.4 408b11-18). Gerson also does not fully explain what intellect itself is or how it works and gives us little evidence for thinking that Aristotle ever envisages the existence of some human intellect that is not a power of the human soul. There is a third prominent account of DA 3.5, according to which this chapter helps to solve a difficulty that arises in DA 3.4. There Aristotle asks: "if the intellect is simple and impassible (apathês) and has nothing in common with anything else...how will it understand, if understanding is to be affected in some way?" (429b22-25) Since Aristotle holds that the intellect and its activity are immaterial and thus seemingly cannot be directly affected by bodies or their qualities and he also thinks that the intellect starts out without possessing any forms or actual characteristics, he needs an account of how our intellect comes to be informed. Many interpreters have thought that Aristotle introduces the productive intellect (nous poiêtikos) in DA 3.5 in order to explain how the receptive or potential intellect of DA 3.4 begins to understand (e.g. Aquinas, lectio 10; Ross, Aristotle 149-150; Rist, 11; Sisko, "Aristotle's Nous and the Modern Mind"). On such a view, the productive intellect's role is to make potential objects of understanding into actual objects of understanding. Aristotle claims at the end of 3.4 that "in those things which have matter each of the intelligibles (ta noêta) exists potentially." (430a5-9) Enmattered things need to be separated from matter in order to be understood and Aristotle introduces the productive intellect to explain how this happens. The productive intellect employs the images (phantasmata) of enmattered things that are in the soul as a result of perception and memory. The productive intellect draws out the Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 17 intelligible forms contained in these images and places these intelligible forms in the receptive intellect. When this happens, understanding (noein) occurs. (Aquinas, lectio 10; Siwek, 330-332) This third account of DA 3.5 results in some sort of human separability since the divine productive intellect is taken to be a power of the human soul. The extent of this separability depends on how one reads the rest of 3.5. If the passible (pathêtos) nous is the nous of DA 3.4 then only the productive intellect is divine and undying. This results in a view of separability similar to Gerson's, where the productive intellect is eternally active but also seems to be separate from individual human intellects. Alternatively, some have taken passible nous to be something distinct from the potential intellect of 3.4, either some lesser cognitive power such as phantasia or just nous insofar as it relates to perceptible things, and thus have maintained that both the potential intellect of 3.4 and the productive intellect of 3.5 are separable from the body.21 This results in a more full fledged separability, since it allows for the possibility of individual human intellects existing and being active apart from the body. The third interpretation, like the other two, faces some difficulties. Caston has claimed that this sort of interpretation invents a gap in Aristotle's account where none exists, just in order to make up something for the productive intellect to do (Caston, "Aristotle's Two Intellects: A Modest Proposal" 200). Further, on this view, the productive intellect is just a power that enables something else to understand, but many have thought it should itself be actively understanding, especially since it is supposed to 21 Polansky seems to lean towards such an interpretation (Polansky, 469), an interpretation which several ancient commentators endorsed (see Blumenthal, 157-60 and 163). W.D. Ross also considers such an interpretation (Ross, De Anima). There are several passages in which Aristotle uses a broader conception of nous that includes phantasia: DA 3.3, 427b-428a5; 3.7 431b2-9; 3.10, 433a9-14; De Motu Animalium 6, 700b17-22. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 18 be essentially active. Such interpretations also need to explain why Aristotle claims that some kinds of nous are undying and always active while others are not. Thus we have three distinct interpretations that present sharply divergent accounts concerning the purpose and nature of DA 3.5 and the possibility of human separability. They each have their strengths and their challenges. Their relative plausibility depends both on questions about how well they can make sense of the textual details of 3.5 and on how credible and attractive their broader accounts of the role played by this chapter are. 5. Conclusion Given the complexity and ambiguity of the texts, scholars' interpretations of nous depend, in large part, on their general commitments concerning Aristotle's view of human nature and our place in the cosmos. Scholars who want a thoroughly naturalistic Aristotle, with no traces of Platonic sympathy and little resistance to materialism, find one.22 On the other side, scholars who interpret Aristotle as countenancing some sort of human separability have been accused of twisting his views to fit with religious doctrines about the soul or of inappropriately Platonizing Aristotle. These interpretive phenomena give rise to a worry that discussion of nous in the DA is nothing more than "a sort of Rorschach Test for Aristotelians: it is hard to avoid the conclusion that readers discover in this chapter the Aristotle they hope to admire." (Shields, "The Active Mind of De Anima iii 5") 22 Indeed, some indicate that discounting or minimizing any non-naturalistic or dualistic features in Aristotle is both a goal of and motivation for their interpretation. After outlining his interpretation of the soul as nothing other than "the form of a natural body," Frede notes that Aristotle's remarks on nous throw "all of this into doubt," but responds that we may stick to the naturalistic view because "it is open to us to assume...that [the] active intellect is not a human intellect, that it is not an integral part of the human soul." (Frede, "On Aristotle's Conception of Soul" 104-5) Here Frede's understanding of Aristotle's metaphysical commitments is clearly presented as driving his interpretation of nous: for Frede's purposes, the important thing is that a naturalistic interpretation of 3.4-5 is possible and thus that Aristotle can still be counted as a good naturalist. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 19 While this is a serious worry, there also some genuine prospects for development that might lead to a measure of consensus or at least to a sharpened dialectic. The best path forward in the debate seems to lie in following Aristotle's advice (DA 2.4) by focusing on the activity of understanding (noêsis) and its objects in order to understand the power of understanding. Achieving greater comprehension of Aristotle's account of the intelligible forms, particularly his characterization of them as universal and unchanging, would help determine how separable human intellectual activity is. Similarly, a better grasp of why and how Aristotle thinks human understanding is connected with images (phantasmata) would help determine whether this connection rules out separability. Finally, further attention needs to be given to comparing the potential nous of DA 3.4, the productive nous of DA 3.5, and the divine nous of Metaphysics Λ 7 and 9-10 in order to better discern their similarities and differences. Scholarly progress in any of these areas would help us to better comprehend Aristotle's carefully developed views on the intellect and human nature.23 23 I would like to thank Samuel Baker for his input on an earlier version of this material and Hendrik Lorenz for his interpretative suggestions concerning the naturalist approach. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 20 Works Cited: Aquinas, Thomas. Commentary on Aristotle's De Anima. Trans. Foster Kenelm, and Silvester Humphries. Notre Dame, IN: Dumb Ox Books, 1954. Barnes, Jonathan. "Aristotle's Concept of Mind." Articles on Aristotle. Eds. J. Barnes, M. Schofield, and R. Sorabji. Vol. 4: Psychology and Aesthetics. London: Duckworth, 1979. 32-41. ---. Aristotle: A Very Short Introduction. Oxford: Oxford University Press, 2000. Blumenthal, Henry. "Nous Pathetikos in Later Greek Philosophy," Oxford Studies in Ancient Philosophy, Supplement (1991): 191-205. Brentano, Franz. "Nous Poiêtikos: Survey of Earlier Interpretations." Essays on Aristotle's De Anima. Ed. Martha C. Nussbaum and Amélie Oksenberg Rorty. Oxford: Clarendon Press, 1995 (Originally published, 1992). 313-342. Burnyeat, Myles. Aristotle's Divine Intellect. Milwaukee, WI: Marquette University Press, 2008. Caston, Victor. "Aristotle's Two Intellects: A Modest Proposal." Phronesis 44 (1999): 199-227. ---. "Aristotle's Argument for Why the Understanding is not Compounded with the Body," Proceedings of the Boston Area Colloquium in Ancient Philosophy 16 (2000), 135-174. ---. "Phantasia and Thought." A Companion to Aristotle. Ed. Georgios Anagnostopoulos. Malden, MA: Wiley-Blackwell, 2009. 322-34. Cohoe, Caleb. "Why the Intellect Cannot Have a Bodily Organ: De Anima III 4." Phronesis 58.4 (2013): 1-31. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 21 Frede, Michael. "On Aristotle's Conception of Soul." Ed. Martha C. Nussbaum and Amélie Oksenberg Rorty. Oxford: Clarendon Press, 1995 (Originally published, 1992). 93-107. ---. "La theorie aristotelicienne de l'intellect agent." Corps et Ame: Sur le De Anima d'Aristote. Ed. Gilbert Romeyer Dherbey. Paris: Libraire Philosophique J. Vrin, 1996. 377-90. Gerson, Lloyd. "The Unity of Intellect in Aristotle's 'De Anima.'" Phronesis 49.4 (2004): 348-373. Granger, Herbert. Aristotle's Idea of the Soul. Boston: Kluwer Academic Press, 1996. Guthrie, W. K. C. Aristotle: An Encounter. Cambridge: Cambridge University Press, 1981. Jaeger, Werner. Aristotle: Fundamentals of the History of his Development. Trans. Richard Robinson. Oxford: Clarendon Press, 1934. Johansen, Thomas Kjeller. The Powers of Aristotle's Soul. Oxford: Oxford University Press, 2012. Kahn, Charles H. "Aristotle on Thinking." Ed. Martha C. Nussbaum and Amélie Oksenberg Rorty. Oxford: Clarendon Press, 1995 (Originally published, 1992). 359-80. Kenny, Anthony. The Metaphysics of Mind. Clarendon Press, Oxford, 1989. Lorenz, Hendrik. "The assimilation of sense to sense-object in Aristotle." Oxford Studies in Ancient Philosophy, 23 (2007): 179–220. Nussbaum, Martha C. and Amélie Oksenberg Rorty, eds. [1992] 1995. Essays on Aristotle's De Anima. First paperback edition, with an additional essay by M.F. Burnyeat. Oxford: Clarendon Press. (Originally published, 1992.) Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 22 Menn, S. "Aristotle's Definition of Soul and the Programe of the De Anima." Oxford Studies in Ancient Philosophy, 22 (2002): 83–139. Modrak, Deborah K. W. "The Nous-Body Problem in Aristotle." The Review of Metaphysics 44.4 (1991):755 774. Pakaluk, Michael. "Commentary on Sisko." Proceedings of the Boston Area Colloquium in Ancient Philosophy 16 (2000): 199-205. Polansky, Ronald M. Aristotle's De Anima. New York: Cambridge University Press, 2007. Plotinus. Plotinus, 7 volumes, Greek text with English translation by A.H. Armstrong, Cambridge, MA: Loeb Classical Library, 1968-88. Rist, John M. "Notes on Aristotle De Anima 3.5." Classical Philology, 61.1 (1966), 8-20. Robinson, H. M. "Aristotelian Dualism." Oxford Studies in Ancient Philosophy 1 (1983):123-44. Ross, W.D. Aristotle. London: Methuen, 1949. ---. "The Development of Aristotle's Thought." Proceedings of the British Academy (1957): 43. ---, ed. and commentary. Aristotle, De Anima. Oxford: Clarendon Press, 1961. Shields, Christopher. "Intentionality and Isomorphism in Aristotle." Proceedings of the Boston Area Colloquium in Ancient Philosophy 11 (1995): 307-30. ---. "The Priority of Soul in Aristotle's De Anima: Mistaking Categories?" Body and Soul in Ancient Philosophy. Eds. D. Frede and B. Reis. Berlin: de Gruyter, 2009. 156-68. Cohoe  Nous in Aristotle's De Anima (forthcoming in Philosophy Compass) 23 ---. "The Active Mind of De Anima iii 5." Supplement to "Aristotle's Psychology." The Stanford Encyclopedia of Philosophy (Spring 2011 Edition). Ed. Edward N. Zalta. URL = <http://plato.stanford.edu/archives/spr2011/entries/aristotle-psychology/>. Sisko, John. "On Separating the Intellect from the Body: Aristotle's De Anima III.4, 429a20-b5." Archiv für Geschichte der Philosophie 81 (1999): 249-67. ---. "Aristotle's Nous and the Modern Mind." Proceedings of the Boston Area Colloquium in Ancient Philosophy 16 (2000): 177-198. Siwek, Paulus, ed. and commentary. Tractatus De Anima; Graece et Latine. Roma: Desclée, Editori Pontifici, 1965. Theiler, W. Aristoteles: Über die Seele, Berlin: Akademie Verlag, 1979. Themistius, On Aristotle's On the Soul, R. B. Todd (trans.), London, Ithaca, NY: Duckworth and Cornell University Press, 1996. Wedin, Michael V. Mind and Imagination in Aristotle. New Haven: Yale University Press, 1988.