Aristotle’s thesis of the relation between soul (psuche) and body can be seen as the apotheosis of his grand philosophical theory of hylomorphism.[1] The metaphysical and psychological basis of his examination of reductive materialism and substance dualism, in particular, is of paramount importance for the elucidation of one of the most difficult aspects of his corpus.
It is necessary first to consider the hylomorphic foundation of Aristotelian psychology and its relations with physicalism and substance dualism, after which, I shall proceed to address problems raised with Aristotle’s theory of ‘nous’ (intellect). Finally, I shall address the question of whether Aristotle was a functionalist.
I
As I have remarked, De Anima argues for a hylomorphic psychology and principally conveys the following propositions:
(i) “Substance is, (a) matter which in itself is not a ‘this’, and (b) form and essence, which is precisely that in virtue of which a thing is called a ‘this’, and thirdly that which is compounded of both (a) and (b).”[2]
(ii) “The body cannot be soul; the body is the subject or matter, not what is attributed to it. Hence, the soul must be a substance in the sense of the form of a natural body having life potentially within it.”[3]
(iii) “The soul is the cause or source of the living body – it is now manifest that the soul is also the final cause of its body. For nature, like mind, always does whatever it does for the sake of something.” [4]
It is clear, therefore, that Aristotle’s conception of the soul-body relation is a hylomorphic account, namely, that the soul is the essential form, and the body the matter: Therefore, the body comes into actual, rather than mere potential being, because matter is actualised by a soul, forming the living organism. So, we have the principal definition of soul – “the first actuality of a natural body having life potentially in it”[5] – this effectively entails that without soul, body could not become living body.
What is of great interest here is that Aristotle thesis of the four causes (from the Physics) resurfaces in hylomorphism, in particular with the formal, efficient and final causes playing an orchestrating role in his psychology: as with his concerns in natural philosophy, Aristotle argues for teleology in the context of his psychology, as “the soul is the final cause or source of the living body”.
With reference to the doctrine of the Four Causes, one can argue that that the soul exists as the formal, efficient and final cause of the body’s existence – i.e., that the biological processes and the physiology of the living organism are actualised by the soul to prolong the survival of the body. Therefore, one has established the following that:
(1) The soul is the “first actuality of a natural body having life potentially in it,”[6] meaning that the soul acts as formal and efficient cause. It is a set of developed capacities to engage in the activity which is the corresponding second actuality. For example:
First potentiality: Aristotle aged two months.
Second potentiality/first actuality: Aristotle (as an adult) sleeping.
Second actuality: Aristotle (as an adult) discussing philosophy.
(2) It is clear that the soul is an integral part of any ‘aition’ of a living being, as it is placed at the centre of understanding how the body comes to be; moreover, it is now manifest that the soul is also the final cause of its body. “For nature, like mind, always does whatever it does for the sake of something – viz., its end”.[7]
(3) Above all, we can now assert that “the soul is inseparable from its body[8] and the rightness of the view that the soul cannot be without a body.”[9]
Now let us turn our attention to the problems posed by reductive materialism and Cartesian dualism: let us first though list the fundamental principles of each thesis.
(a) Hylomorphism: if we do not think that the Athena-shape of a statue persists after the bronze has been melted and recast, we should not think that the soul survives the demise of the body. Therefore, “the soul is inseparable from its body.”[10]
(b) Reductive materialism (physicalism): soul is not a distinct substance from body, and, therefore, soul is ‘homoousios’ with body – i.e. soul is body.
(c) Cartesian dualism: The Argument from clarity and distinctness:
(1) Soul and body are clearly and distinctly ontologically distinct finite substances.
(2) If I can clearly and distinctly conceive of soul and body existing independently of one another, since they are metaphysically separable, then they can exist independently of one another.
(3) I can clearly and distinctly conceive of soul and body existing independently of one another, since they are metaphysically separable.
(4) Therefore, soul and body can exist independently of one another.
Cartesian dualism, however, lacks the bite to damage hylomorphism: firstly, Cartesian psychology and physiology is less ‘sophisticated’ than Aristotle’s theory for a number of reasons:
1. As Gilbert Ryle astutely put it, with the “ghost in the machine”, the putative causal interaction between soul and body is thrown into the wind. With hylomorphism, there is no such objection.
2. Moreover, Descartes’s claim that “soul and body are in an intimate union” lacks the clear unity of the hylomorphic composite of matter and form blended into one organism, simply because of the physical and physiological problem of a non-spatial immaterial substance interacting with a corporeal system.
3. Aristotle’s psychology has its links with his biology, physiology, physics, and metaphysics. Indeed, Cartesian dualism addresses only the issue of the relation of the body to the soul. Hylomorphism, by contrast, addresses the much broader question of just what a substance - any substance - is.
4. Aristotelian psychology plays a crucial role in explaining not only aspects of the science of reality, but also revealing the paradoxical structure of the human condition – namely that we have, like animals, a hylomorphic soul, but somehow we transcend this through our access to the noetic realm of philosophy by virtue of being endowed with incorporeal ‘nous’.
5. Above all, hylomorphism’s greatest blow is evident in its great critique of substance dualism: by itself, hylomorphism gives us no reason to treat souls as separable from bodies, even if we think of them distinct from their material bases. As a result, “the substance dualist’s questions never even get going.”[11] In this sense, clarity and distinctness do not have the epistemic property of truth-guaranteeing.
Reductive materialism (physicalism) is the second threat to hylomorphism – however, it too can be dispatched off:
Physicalists hold that all mental states are also physical states – this claim dates back to the Stoic materialist axiom that ‘nothing can act upon or being acted upon by something else if it is not of the same substance (‘homoousios’).’ Now, if we do not think there is an interesting or important question concerning whether the Hermes-shape and its material basis are one, we should not suppose there is a special or pressing question about whether the soul and body are one. As Aristotle put it, “it is not necessary to ask whether soul and body are one, just as it is not necessary to ask whether the wax and its shape are one, nor generally whether the matter of each thing and that of which it is the matter are one. For even if one and being are spoken of in several ways, what is properly so spoken of is the actuality.”[12]
Secondly, analytic philosophers of mind have claimed that because Aristotle never proposed a mental substance, as had Descartes, this committed him to physicalism. However, this metaphysical assumption is clearly false, since Aristotle's theory is both non-substantialist (i.e., there is no mental substance) and non-physicalist (i.e., the psuche is not completely redescribable in purely physical terms). While soul can be distinct from body, it certainly does not follow that it is ontologically distinct.
In conclusion, though Aristotle agrees with the dualist insofar as that soul and body are distinct, hylomorphism embraces neither reductive materialism nor substance dualism. Instead, it is sui generis as a dialectical synthesis – a ‘dualistic monist’ thesis, claiming that soul and body compromise one ‘ousia’ (substance) together, but soul is not housed in a corporeal prison as Plato had postulated. Rather, “the soul’s natural and best home is in the body.”[13]
Now let us turn to perhaps the most difficult aspect of Aristotelian psychology.
II
Aristotle’s theory of ‘nous’, the doctrine that intellect is incorporeal, eternal and has no bodily organ, has perplexed philosophers for centuries. Indeed, because of the complexity of ‘nous’, some Aristotelians “fear that it commits Aristotle to some form of Cartesian dualism…and that it seems flatly incompatible with his general definition of psuche as form and actualisation of the body.”[14] Let us address the first worry: as we discussed earlier, Cartesian dualism is the doctrine that soul and body are two ontologically distinct substances and are thus capable of existing independently of one another. For Aristotle to be committed to substance dualism, he must claim that the soul is separable from body. However, he does not argue for this; ergo, by Modus Tollens, he is not committed to Cartesian dualism.
Secondly, the worry raised by some Aristotelians emanates from a confusion between the notions of ‘nous’ and ‘psuche’. For Aristotle, contra Descartes, soul (psuche) is not an incorporeal substance, namely intellect. ‘Psuche’ is rather, “the first actuality of a body having life potentially in it.” However, Descartes’s account of ‘psuche’ treats ‘nous’ as its subject matter, transforming soul into intellect, which is a claim Aristotle would clearly have rejected.
Now, the second worry is that ‘nous’ is incompatible with the hylomorphic definition of soul. Again this is simply not the case: though “it is clear that the soul is not separable from the body…nothing prevents some parts from being separable, because they are not the actualisation of any body part.”[15] Using the following categorical syllogism, it is clear that Aristotle denies that his definition of soul applies to ‘nous’:
(1) Whatever is not the actualisation of any body part is separable from body.
(2) Intellect is not the actualisation of any body part.
(3) Therefore, intellect is separable from body.
“Concerning Intellect…this alone can be separated, as the eternal from the perishable.”[16] By describing ‘nous’ as divine and active, Aristotle “clearly means to exclude it from the hylomorphic definition.”[17] And since the definition does not apply to ‘nous’, there is no question of a literal contradiction between the definition and the doctrine of Intellect.
III
Finally, our discussion of Aristotelian psychology has led us to the contemporary debate: “was he a functionalist?”
Functionalism in the philosophy of mind is the theory that mental states are defined in terms of their relations to causal inputs, behavioural outputs, and other mental states. It holds that the same mental state may be realised by several different physical states or processes. Mental states cannot, therefore, be reduced to physical states. They are, rather, functional states of the physical systems that realise them. How advocates of functionalism have argued for its relation to hylomorphic psychology lies in that “…definitions [of any psychological or physiological process] must always be in terms of function, not matter. What makes something human is not what it is made of but what it does.”[18] E.g. a dead eye is no longer an eye, precisely because it cannot see.
Now, there is certainly much evidence in De Anima to support these claims. However, now I would like to draw attention to one key area of functionalism, which has resulted in a tremendous split of opinion:
One of the key implications of functionalism is the computationalist ‘transportability’ thesis, which is the claim that minds can, in principle, be “transported” into any physical system that can be arranged so as to preserve the functional relations. Thus, a human mind could, for instance, be instantiated in an electronic computer, provided the computer was programmed properly. However, the kind of organization Aristotle had in mind was certainly not computational: he is quite clear that the only material object that has the potential to be a living thing is a (biological) body. So, Aristotle’s general definition of ‘psuche’ rejects any computationalist account. Now, does this entail that Aristotle was not a proto-functionalist?
Not entirely: Aristotle might be considered to have been a functionalist in the very general sense that he did not believe it possible to explain life and mind in reductive physiological terms. His definitions of vital processes, such as perception, are functional. E.g. the act of intellection (or noetic awareness) is defined as “the rational structure of the world realised in human (or divine) thought;”[19] And perceptual awareness has the function of realising the qualitative structure of the world in animal sentience.
“There is no hint, however, that he believed, even in principle, that these functions might be ‘lifted out’ of the body in which they are found, and moved or reproduced somewhere else. In this Aristotle is at odds with contemporary functionalism.”[20]
IV
It seems, therefore, that categorising Aristotelian psychology as dualistic, materialistic, or functionalistic fails to grasp its underlying thought. Perhaps the best way to think about his philosophy of soul and the soul-body relation is as a sui generis account. The temptation to assimilate it to our current accounts, partly in an effort to gain for them and air of ancient authority, is ever-present. As far back as the 6th century, John Philoponus noted that “commentators on Aristotle are inclined to try to attribute to him doctrines which they themselves think sound.” Instead of trying to discover how Aristotle comes to be understood by us, as a result of attempts to impose our own theses on his work, one should rather seek how we can bring ourselves to understand Aristotle without the need of marching to contemporary theory. The temptation is strong, but it ought to be resisted.
Bibliography:
Aristotle, De Anima, H. Lawson-Tancred (trans.), Harmondsworth -
Penguin, (1986).
Nussbaum, M. C. & Putnam, H. (1992), ‘Changing Aristotle’s Mind,’ in M. C. Nussbaum and A. O. Rorty (eds.), Essays on Aristotle’s ‘De Anima’,
Khan, C. H. (1992), ‘Aristotle on Thinking,’ in M. C. Nussbaum and A. O. Rorty (eds.), Essays on Aristotle’s ‘De Anima’,
Cohen, S. M. (1992), ‘Hylomorphism and Functionalism,’ in M. C. Nussbaum and A. O. Rorty (eds.), Essays on Aristotle’s ‘De Anima’,
Green, C. D. (1998), ‘The Thoroughly Modern Aristotle: Was He Really A Functionalist?’, History of Psychology, vol. 1, 8-20.
[1] This can be translated simply as “matter-formism”.
[2] De Anima, 412a7-10.
[3] De Anima, 412a17-20.
[4] De Anima, 415b10 & 415b15-17.
[5] De Anima, 412a9.
[6] Aristotle, De Anima, II 1 412a9.
[7] Ibid, 412a11.
[8] Aristotle, II 1 412a27.
[9] Ibid, II 3, 414a19-20.
[10] Aristotle, II 1 414a4.
[11] M. C. Nussbaum and H. Putnam, ‘Changing Aristotle’s Mind’, in C. Nussbaum and A. O. Rorty (ed.), Essays on Aristotle’s ‘De Anima’, p Ibid, p.56.
[12] Aristotle, De Anima II, 1 412b6-9.
[13] Nussbaum and Putnam, p.54.
[14] C. H. Khan, ‘Aristotle on Thinking’, in M. C. Nussbaum and A. O. Rorty (ed.), Essays on Aristotle’s ‘De Anima’, p.360.
[15] Ibid, 413a4.
[16] Aristotle, De Anima, II 1 413b24.
[17] Khan, p.361.
[18] S. M. Cohen, ‘Hylomorphism and Functionalism’, in C. Nussbaum and A. O. Rorty (ed.), Essays on Aristotle’s ‘De Anima’, pp 59-60.
[19] Kahn, p.375.
[20] C. D. Green, The Thoroughly Modern Aristotle: Was He Really A Functionalist?, p.19.
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