By João Pinheiro da Silva, a master’s student in philosophy at CEU Vienna.

1. Hylomorphic Dualism: A Pair of Jeans

In a recent article, Aristotelian Dualism, Good; Aristotelian Hylomorphism, Bad (2021), Howard Robinson argues that there is both a fashionable - although certainly wrong – and an unfashionable – and most certainly right – aspect of Aristotle’s philosophy of mind and its reception in contemporary philosophy. The first - “fashionable” - aspect stresses hylomorphism as a way of dissolving the mind-body problem whereas the latter – unfashionable – Aristotelian idea concerns his thesis according to which the intellect is immaterial.

As Robinson puts it, it is common for modern Aristotelians, who otherwise have a high view of Aristotle’s relevance to modern philosophy, to treat this argument [for the immateriality of the intellect] as being of purely historical interest, and not essential to Aristotle’s system as a whole” (Robinson 2021: 295). This happens because the contemporary resurgence of hylomorphism is animated by an attempt to dissolve classical problems of modern philosophy – such as the mind-body problem - by restating a different philosophy of nature, one that could supposedly save us from a vast array of Cartesian errors. Dualism often ranks high among these cartesian errors and, if contemporary philosophers have any problem with Aristotle’s arguments for the immateriality of the intellect, it is because they see a threat of dualism embedded in them. 

However, if “modern Aristotelians” have a problem harmonizing hylomorphism with the arguments for the immateriality of the intellect, this was certainly not a problem for Aristotle himself who saw no inherent contradiction in holding both that:

1. The human soul is the form of the human body - Anima forma corporis; and

2. The human soul is immaterial.

The conjunction of these two propositions thus outlines another option for an Aristotelian philosophy of mind. This position can be called “Hylomorphic Dualism” and it maintains the hylomorphic apparatus according to which the soul is the form of the body while, at the same time, stressing the immateriality of the human intellect. 

Hylomorphic dualism is supported by a long-lasting interpretative tradition that counts with Thomas Aquinas at its head. This tradition relies on a specific reading of the account of the Active Intellect in De Anima iii 5. According to Christopher Shields, Aquinas interprets these passages as “a vindication of the compatibility of personal immortality and soul-body hylomorphism” (Shields 2020). Aquinas argues that the arguments for the immateriality of the intellect also entail its immortality and thus its capacity to survive separated from the body. Whether or not this is the correct reading of Aristotle is a matter of dispute (Ibid.) but, either way, Aquinas’ interpretation of Aristotle formulates a cohesive argument that builds on both hylomorphism and thesis of the immateriality of the intellect.

Hylomorphic dualism is “dualist” in the sense that the soul—or the intellect—and the body are as mutually irreducible and, on top of that, the soul is conceived as immaterial. However, body and soul are not seen as substances in their own right. The soul is rather the substantial form of the body, that by virtue of which the substance it informs—in the case, human beings—carries out his distinctive activities. And the body is what provides the potential for those activities to actually occur. Human beings are thus conceived as a unified whole, as rational animals, not as a composite of two different substances. 

We could thus say, going back to Robinson’s formulation, that hylomorphic dualism is just like a pair of jeans: it is not exactly fashionable nor outright unfashionable. And just like a pair of jeans, one can never go wrong with it, it is always a great fit. Hylomorphic dualism manages to keep the best insights from both hylomorphism—its unified account of the human being—and dualism—the immateriality of the intellect—, building a cohesive account of human beings that avoids the problems that arise for other forms of dualism.

2. Some Initial Problems for Hylomorphic Dualism

There are, however, some apparent problems or inconsistencies with hylomorphic dualism that should be dealt with before proceeding. Hylomorphic dualism seems to be a rather ad hoc – and Christian - stipulation on the general Aristotelian picture of nature. After all, hylomorphism holds that every substance is a unified composite of form and matter. So, why is there an exception for the human soul? How can the form of human beings exist apart from what it informs?

In dealing with these questionings, one must first reckon that Aristotle himself recognizes the existence of immaterial “Intelligences” that move the heavenly spheres. These are pure forms that resemble Aquinas’ later account of angels. So, there is space in the Aristotelian system for the possibility of pure forms outside the prime mover and this possibility can be extended to the human soul itself depending on our reading of De Anima iii 5. This becomes clearer in Aquinas who argues, in the Ente et Essentia (chapters 4–5), that the angels and the human soul are forms conjoined with an “act of existing”. That is, they are not exactly forms that exist by themselves because, according to Aquinas, only God is capable of such a feat, but they are forms without matter. So, Aristotelian—and Thomistic—hylomorphism does not exclude that possibility from the outset.

But one can still ask why this applies specifically to the human soul? What is the difference between the human soul and any other soul? Why can a human soul survive the death of the body but dog’s soul cannot? This is where Aristotle’s arguments for the immateriality of the intellect enter the picture. As Robinson puts it, Aristotle claimed that “the intellect must be immaterial because, if it were material, it could not receive all forms [… and] if the intellect were in a physical organ, it could be sensitive only to a restricted range of physical things; but this is not the case, for we can think about any kind of material object, as well as non-material objects. As it does not have a material organ, its activity must be essentially immaterial” (Robinson 2021: 295). It is this capacity to carry out immaterial operations that distinguishes the human soul from a dog’s – or a plant’s - soul. Human beings carry out immaterial operations that sets them apart from other composites of matter and form. The immaterial aspect of the sou—the intellect—can thus operate and subsist apart from matter, even if not as a complete substance.

So, hylomorphic dualism is not a mere ad hoc stipulation on hylomorphism but is rather a theory that directly follows from taking seriously Aristotle’s arguments concerning the immateriality of the intellect.

3. Hylomorphic Dualism versus Substance Dualism

Hylomorphic dualism thus takes seriously the dualistic arguments concerning the immateriality of the intellect. However, this does not mean that hylomorphic dualism is the same as other versions of dualism.

Eric T. Olson (2001) distinguishes two forms of dualism: pure substance dualism and compound substance dualism. Pure substance dualism holds that even though “the material object by which you perceive and act in the physical world – the thing we call your body – may be as intimately connected with you as you like; […] it is not a part of you” (Ibid., 1). That is, I am indeed a simple substance because I am identical to my soul. I am thus a mental substance, or a res cogitans, or a soul. On the other hand, compound substance dualism holds that “both soul and body are parts of you, though only the soul is essential to you” (Ibid.). This means that “you could outlive your body” even though your body is a proper part of you.

Contemporary dualists, such as Richard Swinburne (2019), tend to side with the latter form of dualism: compound substance dualism. Swinburne argues that human beings are composed of body and soul; however, the human soul is immaterial and, thus, capable of surviving bodily death. This may seem similar to Aquinas hylomorphic dualist position (and Swinburne himself thinks it is; see Swinburne 2019: 80-84) but there is a crucial difference between the two positions.

As Jeremy W. Skrzypek puts it: “On Swinburne’s theory of the human person, human persons are compound substances […] composed of both a physical substance (a human body or human organism, itself a compound substance composed of various smaller physical substances) and a mental substance (an immaterial soul, itself a simple substance) [… In this picture,] I am neither my body nor my soul. I am something composed of both body and soul […] By virtue of being composed of a human body, I possess all of those physical properties that my body possesses. And by virtue of being composed of an immaterial soul, I possess all of those mental properties that my soul possesses” (Skrzypek 2021: 104-105). This may seem like an uncompromising position that can synthetize, at the same time, the arguments for the immateriality of the soul without embracing a form of pure substance dualism that disregards the body as a real part of human beings. But Swinburne’s position suffers from the problem that Olson (2001) diagnosis in the various forms of compound substance dualism. Who or what is it that perceives, thinks, remembers, imagines, etc., according to Swinburne? Is it the soul who has these intentional states or the body-soul composite? Swinburne would say that given that we are composed of both body and soul, it is this body-soul composite that perceives, thinks, remembers or imagines whenever I perceive, think, remember or imagine. But given his view of the soul as a separate substance that is responsible for our mental happenings, there seems to be two thinkers in the mix: the thinking substance and the body-soul composite. As Olson (2001, 75) argues: “. . . compound dualism entails that there are at least twice as many thinking things as we thought there were. You are a compound of a body and a soul. But that soul is itself rational and conscious. So there are two thinking things sitting in your chair, a soul and a compound, reading an essay that was co-written by simple and a compound philosopher.” Swinburne’s dualism has “too many things doing all of the things that I do”, “too many things doing my thinking” (Skrzypek 2021: 106). On top of that, if we conceive of personhood as something tied to consciousness, “then both me and my soul possess that essential capacity […] and so we both count as persons” (Ibid.).

Compound substance dualism seems to entail various mereological problems. Even though it tries to give us a unified theory of human beings as both bodily animals and beings that can engage in immaterial activities, it ultimately fails to do so.

At first sight, hylomorphism appears to run into the same problems that compound substance dualism does. If the soul is an immaterial form that can persist the death of the body, then we could also ask whether it is the intellect who thinks or the human being composed of soul and body. But the hylomorphic account of substance helps the hylomorphic dualist avoid this problem. Robinson dismissively points out that “modern Aristotelians” “emphasize that [Aristotle] was not a “Cartesian” dualist, because the intellect is an aspect of the soul and the soul is the form of the body, not a separate substance” (Robinson 2021: 295). But even if these “modern Aristotelians” are wrong in dismissing the Stagirite’s arguments concerning the immateriality of the intellect, they are right in pointing out that they hylomorphic account of substance distances him from traditional substance dualists. 

According to hylomorphic dualism, the soul not a complete substance but the substantial form of a substance – the human being. And it is the human being – not his soul or intellect – who perceives, thinks, sees, smells, remembers, imagines. According to Aquinas, only substances act in the primary sense. We can say that parts of substances act but only through the means of them:

the eye or the hand cannot be said to subsist per se; nor can it for that reason be said to operate "per se." Hence the operation of the parts is through each part attributed to the whole. For we say that man sees with the eye, and feels with the hand, and not in the same sense as when we say that what is hot gives heat by its heat; for heat, strictly speaking, does not give heat. We may therefore say that the soul understands, as the eye sees; but it is more correct to say that man understands through the soul. (Aquinas, Summa Theologica I q. 75 a. 2 ad 2)

The Aristotelian-Thomistic picture is “substance-centric” (Cory 2021: 75) and understands human beings as a single unified substance. Swinburne’s conception of substance, on the other hand, makes it so that “the order of explanation is reversed. For Swinburne, I think because my soul thinks, whereas on Aquinas’s account there is a sense in which my soul thinks because I think” (Skrzypek 2021: 114). 

These different visions of dualism also lead to two different conceptions of the soul after death. Aristotle and Aquinas vision of the body and soul as the matter and form of a single substance makes them to pose that, even though the soul can operate without being conjoined to the body, it can only do so in a limited way that deeply differs from its natural state when united to the body. That is, when conjoined with the body, the soul does not operate independently of it. Both Aristotle and Aquinas stress that soul powers such as sensation and imagination have a material basis. Only the intellect is immaterial. Thus, contra the other two forms of substance dualism, hylomorphic dualism does not entail that the soul after death operates in the same way as when conjoined with the body, in fact, it presupposes that it does not: “after death the soul no longer has available to it its normal input from sensation and imagination.  If it is to think while disembodied, then, it must do so in a very different manner.  What this involves, for Aquinas, is “turning to simply intelligible objects” rather than to phantasms” (Feser 2011).

Thus, according to Aquinas, when the body dies and the soul carries on, we are not dealing with the essence of the human being or his “proper part”. Instead, the postmortem soul is a “residue of the human being” (Feser 2020) that is a unified substance. It is thus an incomplete substance in an unnatural state. Hylomorphic dualism can thus avoid the problems with compound substance dualism that we saw exemplified in Swinburne. Hylomorphic dualism does not entail giving two contradictory answers to questions such as “Who or what is it that perceives, thinks, remembers, imagines?”. One can just say that, when the soul is in its natural state, that is, conjoined with the body, it is the human being composed of soul and body and soul that perceives, thinks, remembers, imagines. When the soul operates on its own, it does so in a different way than when conjoined with the body – in a disembodied way.

Bibliography

Aquinas, T. (1920). Summa Theologica. New Advent.

Cory, T. (2021). Aquinas and “I”. Em P. Kitcher, The Self: A History (pp. 73-98). Oxford: OUP.

Feser , E. (25 de August de 2011). Vallicella on hylemorphic dualism, Part III. Obtido de Edward Feser: http://edwardfeser.blogspot.com/2011/08/vallicella-on-hylemorphic-dualism-part_25.html 

Feser, E. (February de 2020). Soul Proprietor. Obtido de First Things: https://www.firstthings.com/article/2020/02/soul-proprietor 

Oderberg, D. (2007). Real Essentialism. New York: Routledge.

Olson, E. T. (2001). A Compound of Two Substances. Em K. Corcoran , Soul, Body, and Survival: Essays on the Metaphysics of Human Persons (pp. 73-88). Cornell: Cornell University Press.

Robinson, H. (2021). Aristotelian Dualism, Good; Aristotelian Hylomorphism, Bad. Em P. Gregoric, & J. Fink, Encounters with Aristotelian Philosophy of Mind (pp. 283-306). New York: Routledge.

Shields , C. (2020). The Active Mind of De Anima iii 5. Obtido de Stanford Encyclopedia of Philosophy: https://plato.stanford.edu/entries/aristotle-psychology/active-mind.html 

Skrzypek, J. (2021). Not Just A Terminological Difference: Cartesian Substance Dualism Vs Thomistic Hylomorphism. Roczniki Filozoficzne 69, 1 , 103-118.

Swinburne, R. (2019). Are We Bodies or Souls? Oxford: Oxford University Press.