On David Oderberg's hylemorphic dualism

Why the name Hoc Aliquid? I've noticed that quite a few philosophy journals are named after random philosophical terms that have little to do with the journals' actual content. Phronesis is devoted to ancient philosophy in general, not just the ancient concept of practical reason. The Proceedings of the Aristotelian Society doesn't limit itself to discussing Aristotle. The Monist has nothing to do with monism, nor The Dualist with dualism. I've decided to break with tradition by naming my blog after a philosophical term that accurately describes it: hoc aliquid, an expression from medieval scholastic philosophy meaning "this something".

Below is my first blog entry, on David Oderberg's hylemorphic dualism. (If you're already familiar with Aristotelian terminology (matter, substantial form, etc.), you may want to read the intro and then skip to section 3, where the most interesting discussion takes place.)

1. Introduction

Thomas Aquinas was a smart guy, although (like every philosopher) he had his bad days.[1] With the recent revival of virtue ethics, some philosophers have dared to introduce Thomistic ethical thought into secular philosophy. Yet it takes a special sort of chutzpah to propose Aquinas's theory of the soul as an option in modern theory of mind.

In his paper "Hylemorphic Dualism", David Oderberg defends such a theory of mind. (The paper has been published in print, but it can be found online.) The theory is "hylemorphic", since it claims that the soul is related to the body as form (morphe) to matter (hyle). Yet it is a kind of dualism, since it claims that the soul performs a non-bodily operation (namely thought) and can exist apart from the body. Oderberg claims that his hylemorphic dualism is "the dualism of Aristotle and the Aristotelians, most notably St. Thomas Aquinas and his followers".[2]

In this essay, I critique Oderberg's presentation of hylemorphic dualism.

2. Hylemorphic dualism

Oderberg lays out his basic theory in one paragraph:

(1) All sub­stances, in other words all self-subsisting entities that are the bearers of properties and attributes but are not themselves properties or attributes of anything, are compounds of matter (hyle) and form (morphe). (2) The form is substantial since it actualizes matter and gives the substance its very essence and identity. (3) The human person, being a substance, is also a compound of matter and substantial form. (4) Since a person is defined as an individual substance of a rational nature, the substantial form of the person is the rational nature of the person. (5) The exercise of rationality, however, is an essentially immaterial operation. (6) Hence, human nature itself is essentially immaterial. (7) But since it is immate­rial, it does not depend for its existence on being united to matter. (8) So a person is capable of existing, by means of his rational nature, which is traditionally called the soul, independently of the existence of his body. (9) Hence, human beings are immortal;[3] but their identity and individu­ality does require that they be united to a body at some time in their existence.

A couple of clarifications before we continue:

First of all, when Oderberg says that a person's soul is the person's "rational nature", he doesn't mean that the soul consists solely of the property of rationality. A person's soul is the person's substantial form. The person's substantial form is the person's one and only nature, which gives the person all of his essential properties, not just rationality. As Oderberg puts it, "for any substance, there is one and only one substantial form that it possesses. This is because a substance is one kind of thing, and substantial form determines the kind of thing it is."[4]

Second of all, it's important to note that Oderberg doesn't deny souls to non-rational animals—or even to plants. "Soul" is simply a label for the substantial form of a living thing, whether or not it has reason. He argues, however, that only the intellectual (i.e. human) soul is immortal.

3. Operations of the soul

My first complaint is that Oderberg doesn't distinguish clearly between operations of the soul and operations of the ensouled body.

A person's soul or substantial form gives the person all of his essential properties. These properties include the ability to perform various operations, such as nutrition, sensation, and thought. Most of these operations are performed by the body. For example, nutrition is a process in which the body assimilates food. However, according to Oderberg, one of these operations—namely thought—is not a bodily operation. Thought is an operation performed by the soul.

Now consider the following passages:

Human nature [i.e. the human soul], being essentially immaterial, contains a power of nutrition that can exist apart from any embodiment. But in the absence of the requisite mate­rial conditions— embodiment and objects upon which to act— that power cannot be exercised. [...]

Growth, nutrition, reproduction, sentience, perception—all of the operations of the organism belong to the unique human nature [i.e. human soul] of the person. […] Some of those oper­ations, however, depend essentially on matter—such as reproduction and sensation—and others, such as the operations of the intellect, as we have seen, do not.

It's clearly misleading to say that nutrition and thought are both powers or operations of the soul. The soul performs the act of thinking, but it doesn't perform the act of nutrition; rather, the body does. Thus, thought is an operation of the soul, but nutrition is not, strictly speaking, an operation of the soul. What Oderberg should say is that nutrition (and sensation, etc.) belong to the body by virtue of the soul, whereas thought belongs to the soul itself.[5]

4. Immortality of the soul

In my opinion, the biggest problem with Oderberg's account concerns his argument for the soul's immortality—or, more precisely, its separability from the body:

If x can operate without y, albeit perhaps imperfectly, then x must have a nature that can be actual without y's being actual. But for x to be actual is for x to exist, and for y not to be actual is for y not to exist. […] Since the human soul can operate without matter [i.e. by thinking], it can exist with­out matter. It might exist in an imperfect state, since it cannot, for instance, perform acts of sensation that require material stimuli and the formation of mental images, but it can still exist apart from matter.

One of the problems with this argument is that the phrase "x can operate without y" is ambiguous. It could mean either of two things:

1. x can operate in separation from y. 
2. x can perform an operation in which y doesn't participate. 

If we interpret the phrase in the first way, then it clearly entails that x can exist in separation from y. (Clearly, if x is operating in separation from y, then x already exists in separation from y.) The trouble is that Oderberg doesn't give any argument for the claim that the soul can operate in separation from the body.

Suppose we interpret the phrase in the second way. We already know that, according to Oderberg, the body doesn't participate in one of the soul's operations, namely thought. Does it follow that the soul can exist apart from the body? It isn't obvious that this should follow.

Aquinas provides a bit more argument on this point than Oderberg does:

The intellectual principle which we call the mind or the intellect has an operation 'per se' apart from the body. Now only that which subsists can have an operation 'per se.' For nothing can operate but what is actual: for which reason we do not say that heat imparts heat, but that what is hot gives heat. We must conclude, therefore, that the human soul, which is called the intellect or the mind, is something incorporeal and subsistent (Summa Theologiae 1.75.2).[6]

Aquinas's reasoning is as follows. Only "subsistent" things can perform operations of their own. For example, the property of heat (which is not a subsistent thing) doesn't perform the operation called "giving heat". Rather, a hot object (which is a subsistent thing) gives heat. The soul performs an operation of its own. Therefore, the soul must be a subsistent thing, capable of existing on its own.

Even if we read Aquinas's argument into Oderberg, does Oderberg succeed in convincing us that the soul can exist apart from the body? I don't think so. 

According to the dominant interpretation of Aristotle, form is individuated by matter. That is, when there are multiple forms of the same kind, the forms remain distinct from each other only because they are attached to different bits of matter. For example, the substantial form of Whiskers the cat remains distinct from the substantial form of Fluffy the cat only because Whiskers and Fluffy consist of different bits of matter.

Not all scholars agree with this interpretation of Aristotle,[7] but Oderberg does: he says that "form is not of itself individual" and that "the identity of a substance is given by the form as instantiated in matter". Now we face a problem: how can an individual soul exist apart from the body, if form is individuated by matter?

Clearly, Oderberg thinks that the disembodied soul's immortality is secured by its ability to perform the non-bodily operation of thought: "(5) The exercise of rationality, however, is an essentially immaterial operation. (6) Hence, human nature itself is essentially immaterial. (7) But since it is immate­rial, it does not depend for its existence on being united to matter."

Sorry, but I just don't see a good argument here. The argument "The soul performs a non-bodily operation. Therefore, it is exempt from the rule that forms require matter for individuation" strikes me as a total non sequitur. Moreover, if the soul doesn't depend on matter for its existence, then it seems that the soul should be able to exist without ever having been united to matter. Yet Oderberg says that the soul's ability to exist as an individual "can only be made possible by its once having been the form of a body". 

Elsewhere (Dowd 2009) I've argued that Aristotle can explain how the soul's ability to think allows the soul to exist apart from its body. The argument can be summarized as follows. For Aristotle, "matter" is a relative term. The question is not "Is X matter?" but, rather, "What is X's matter?" X's matter is whatever stuff is potentially X. (For example, a bronze statue's matter is the bronze that the statue is made of.) Now, a soul is potentially a thinking soul. Therefore, a thinking soul has matter, namely a soul. When separated from the body, the soul might continue to think (since thinking is an operation of the soul itself, not of the body). Therefore, when separated from the body, the soul might have matter. And if it has matter, then it can continue to exist as an individual.[8]

Unfortunately, Oderberg doesn't provide any such argument. And in the absence of such an argument, it remains mysterious how the immaterial nature of thinking proves that the soul can exist apart from the body.

References:

Caston, Victor. "Aristotle's Two Intellects: A Modest Proposal". Phronesis 44.3 (1999):199-227.

Cohen, S. Marc, "Aristotle's Metaphysics", The Stanford Encyclopedia of Philosophy (Spring 2009 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/spr2009/entries/aristotle-metaphysics/>.

Dowd, Joseph. "Aristotle and the Mind-Body-Soul Problem". Harvest Moon (2009): pp.?? [Harvest Moon is the undergraduate philosophy journal at UC Berkeley. Unfortunately, I don't have my copy of that issue of Harvest Moon on me, so I can't check the page range.]

Oderberg, David. "Hylemorphic Dualism". New Dualism Archive. Accessed April 10, 2011 <http://www.newdualism.org/papers/D.Oderberg/HylemorphicDualism2.htm>.

Spade, Paul Vincent, "Binarium Famosissimum", The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/fall2008/entries/binarium/>.

Thomas Aquinas. Summa Theologica. Trans. Fathers of the English Dominican Province. Ed. Kevin Knight. New Advent. Accessed April 10, 2011 <http://www.newadvent.org/summa/>.

Wedin, Michael V. "Tracking Aristotle's Nous". Aristotle: De Anima in Focus. Ed. Michael Durrant. NY: Routledge, 1993. 128-61.

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[1] In Summa Theologiae 1.102.1, he gives the follow argument for the claim that the earthly paradise is in the east: (1) in De Caelo, Aristotle calls the east "the right hand of the heavens"; (2) the right hand is nobler than the left; (3) therefore, the earthly paradise is in the east.

[2] The theory certainly is Thomistic, or at least relies heavily on Thomistic vocabulary. The extent to which it reflects Aristotle's views is less clear. However, I think it's a better interpretation of Aristotle than certain modern interpretations that deny the soul any kind of immortality (see Caston 1999 and Wedin 1993; I have argued against such views in Dowd 2009).

[3] Oderberg seems to have spoken carelessly here. According to Oderberg, a human soul is a human being's substantial form. A human being's substantial form is not itself the human being; rather, it's what makes matter into a human being. Thus, it's nonsensical to say that a human being is immortal just because his soul is immortal. Aquinas himself insists that a disembodied soul is not a human person.

[4] Here Oderberg accepts Aquinas's theory that each substance can have only one substantial form. Some—indeed, most—of Aquinas's contemporaries thought that a single substance can have various substantial forms, corresponding to the substance's various properties. See Spade 2008 for more details.

[5] In this case, Oderberg is simply following a long Aristotelian tradition. Aristotle himself refers to non-intellectual (and hence bodily) functions as "powers of the soul" (e.g. De Anima 2.3), and so does Aquinas (e.g. Summa Theologiae 1.77). However, Aquinas at least clarifies that the soul's intellectual power has the soul as its "subject", whereas the other powers do not (Summa Theologiae 1.77.5).

[6] From the translation at New Advent (http://www.newadvent.org/summa/)

[7] See Cohen 2009, section 10.

[8] Since writing Dowd 2009, I've decided that, for Aristotle, the disembodied soul might have matter even if it doesn't think. After all, a soul (considered in abstraction from either thinking or non-thinking) is potentially a non-thinking soul just as much as it's potentially a thinking soul.