Friday, November 29, 2019

Was Aquinas a property dualist?


One must always be cautious when trying to relate Aquinas’s position on some philosophical issue to the options familiar to contemporary academic philosophers.  Sometimes he is not addressing quite the same questions they are, even when he seems to be.  Sometimes he does not use key terms in the same ways they do.  And he is working with a general metaphysical picture of the world – in particular, a picture of the nature of substance, essence, causation, matter, and other fundamental notions – that is radically different from the options familiar to contemporary philosophers, in ways the latter often do not realize.

Having said that, let me propose tentatively that there is a way that contemporary philosophers of mind might naturally fit Aquinas’s position on the mind-body problem into the framework of options they are familiar with – a way that is surprisingly neglected by them, even though it is pretty clearly implied by the way they tend to classify the options.

The usual classification goes something like this.  Descartes got the modern discussion of the mind-body problem going by putting forward his famous version of substance dualism.  For Descartes, there are two irreducibly different kinds of substance.  One of them is matter, conceived of as res extensa or extended substance.  The other is mind, conceived of as res cogitans or thinking substance.  The nature of each is entirely exhausted by extension and thought, respectively, and neither has any of the attributes of the other.  Res extensa doesn’t merely have extension, but just is pure extension, utterly devoid of thought or consciousness.  Res cogitans doesn’t merely have thought, but just is pure thought, utterly devoid of extension.

Either one of these substances could exist in the absence of the other.  (That’s why each counts as a substance.  Each has an independent or freestanding existence relative to the other.)  A res extensa by itself and in the absence of a res cogitans would, even if it had all the physical and behavioral characteristics of a human body, be as devoid of thought and consciousness as a stone or a table.  It would be a “zombie,” in the sense familiar in contemporary philosophy of mind.  A res cogitans by itself and in the absence of a res extensa would be essentially like an angelic intellect.  A human being is a composite of these two kinds of substance, the result of their getting into a relation of efficient causal interaction.

Later modern philosophers do not all entirely agree with Descartes’ characterization of matter or of mind, but, to oversimplify a bit, they can be understood as essentially beginning with Descartes’ bifurcation and then modifying it in different ways.  One way to modify it is to keep res cogitans but deny that res extensa is real.  All that exist, on this view, are minds and their ideas, and tables, chairs, rocks, trees, and the like are really just collections of ideas.  Only mental substances and mental attributes are real, and physical objects are real only in the sense that they can be reduced to ideas, which are mental attributes.  This is the idealism spelled out in different ways by thinkers like Leibniz and Berkeley.

Another way to modify Descartes’ picture is to keep res extensa instead and get rid of res cogitans.  On this approach, all that exist are material substances and material attributes, and thoughts, experiences, and the like are, if they are real at all, really just material attributes of some sort (neurological attributes, or computational attributes, or behavioral dispositions).  Minds are real only insofar as they can be reduced to, or shown entirely to supervene upon, matter.  This is the materialism spelled out in different ways by behaviorists, identity theorists, functionalists, and (in the most extreme version, which denies the reality of the mind altogether) eliminativists.

A third alternative to Descartes is to reject both res extensa and res cogitans, and hold instead that there is some third kind of substance that is the only kind that really exists.  What we think of as res extensa or res cogitans is really just this third kind of substance conceived of under different descriptions.  One way to spell this out is the dual aspect theory of Spinoza, and another is the neutral monism of Bertrand Russell.

Then there is the view developed in recent philosophy of mind according to which there is only one kind of substance – namely material substance – but that at least some material substances have two irreducibly different kinds of attributes, namely material attributes and non-material mental attributes.  On this view, materialism is right to deny a dualism of substances and to insist that material substances alone are real, but Descartes was right to insist on a dualism of attributes.  This view is sometimes called attribute dualism or, more commonly, property dualism.

Now, Aquinas certainly would not agree with any of these views.  He was an Aristotelian hylemorphist, and thus would reject the desiccated mathematicized conception of matter that Descartes and his successors put in place of hylemorphism.  He would reject Descartes’ substance dualism as too similar to the Platonic conception of the soul’s relationship to the body, which he was keen to reject.  He would reject the claims that only mind is real, or that only matter is real, or that only some third kind of thing that is neither mind nor matter is real.  And he would reject the property dualist claim that only material substances are real, albeit some of them have non-material properties.  (Into the bargain, he does not use the term “property” the same way that contemporary philosophers do, but that is a secondary point.)

It seems to me, however, that there is a sense in which Aquinas might arguably be classified as a property dualist, though certainly not a property dualist of the usual kind.  Again, contemporary property dualists hold that only material substances exist.  Aquinas disagrees with that, in part because he thinks that there are purely immaterial intellectual substances (namely angels).  But I think he would also reject the suggestion that a material substance could have non-material properties.  For Aquinas, the world exhibits an ontological hierarchy, from purely material things at the bottom to God at the top.  Things higher up in the hierarchy can be the source of things lower down, but not vice versa.  And a material substance with immaterial properties would seem to violate that principle.  It would be like an inorganic substance with vegetative properties.  Such a thing simply wouldn’t really be inorganic, and a material substance with immaterial properties simply wouldn’t really be a material substance.

But what about human beings, you ask?  Doesn’t Aquinas think of them as material substances with immaterial properties?  I’m inclined to say that that is not quite his view, or not quite what his view should be, given his broader metaphysical principles.  This is where the neglected option that contemporary philosophers of mind might have seen, but seem not to, comes in.  The idea of a material substance with both material and non-material properties is only one of two possible ways of spelling out property dualism.  Another way of doing so would be in terms of the idea of an immaterial substance with both material and non-material properties.  And that, I suggest, is essentially what Aquinas took a human being to be.

As I have argued elsewhere, most recently in an essay for the Blackwell Companion series, the Thomistic thesis that the soul is the form of the body is often misunderstood.  Many people read it as saying that the soul is the form of a substance that is entirely bodily, just as the soul of a dog or a tree is the form of a substance that is entirely bodily.  Then they find it puzzling that Aquinas could go on to say that the human soul subsists after death.  For how could the human soul continue after death if it is the form of the body and the body is gone, any more than the soul of a dog or of a tree could subsist after death?

But this misunderstands the Thomistic thesis.  The human soul is the form of a substance which has both bodily operations (like breathing, walking, seeing, etc.) and non-bodily ones (like thinking).  Because it is what gives the substance in question the bodily operations in question, it is, naturally, the form of the body.  But it doesn’t follow that the substance in question is entirely bodily, the way that a dog or a tree is.  It is not.  Even when alive, part of what we do (thinking and willing) isn’t entirely tied to the body in the first place.  That’s why the death of a human being does not entail his annihilation.  He carries on in a highly truncated state, reduced to his intellect and will – as an incomplete substance, as Aquinas says. 

And what kind of incomplete substance is that?  An immaterial one, naturally, since the body is gone.  As Aquinas writes:

It must necessarily be allowed that the principle of intellectual operation which we call the soul, is a principle both incorporeal and subsistent…

[T]he 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.

End quote.  Now, a human being is one substance, not two.  Again, Aquinas rejects the Platonic view of the soul and would reject the Cartesian substance dualist view as too similar to it.  But a human being is not an angel, because angels have no bodily properties or operations at all and human beings do.  The implication seems clearly to be that a human being is an immaterial substance that has material or bodily operations and properties as well as immaterial ones.  In which case Aquinas is a property dualist of a sort.  And notice here that “property” in Aquinas’s sense of that term (and not just in the contemporary analytic philosopher’s sense of the term) is indeed the right word, because our bodily activities (again, breathing, walking, seeing, etc.) are indeed proper to us.  They are proper accidents of a human being rather than merely contingent ones.  A human being in his mature and healthy state will exhibit these bodily properties, which is why death is for Aquinas not a liberation (as it is for Plato).  It is, as I have put it elsewhere, something like a “full body amputation” – the loss of all of the bodily properties that a complete and fully functioning specimen of our kind would exhibit, leaving only the non-bodily properties.

Again, I say this tentatively.  Aquinas was not addressing precisely the issues contemporary philosophers are, and he does not use the relevant terminology in exactly the same way.  So a claim like “Aquinas was a kind of property dualist” is bound to be easily misunderstood.  It is bound to raise in some people’s minds connotations that I do not intend and that Aquinas would not accept.  But it seems to me that, suitably qualified, there is a sense in which it is true.

Further reading:




32 comments:

  1. Ed have you by any chance listened to the recent Unbelieveable? Episode where panpsychism came up?

    I really need to nag Justin to get you on that show again.

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  2. Also do you know the recent conference you were at will be available on YouTube or podcast or something?

    You and Barr always seem to be good sparring partners

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    1. It wasn't filmed, but the essays might be in a future issue of ACPQ. Don't know for sure yet, though.

      But let's not threadjack! (Panpsychism is on topic, though. Didn't hear the episode.)

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    2. Thanks!

      It was a pretty good defence of panpsychism actually. Made all of the same points you do about seeing the mathematics from physics as exhaustively describing matter. It's starting to be a position a lot of people take for granted now so I think the Thomists are going to start to see more and more common ground with philosophers of mind.

      Although most of the conversation was about consciousness. I'd imagine a Thomist like yourself would point to the determinancy of the intellect as something the panpsychist will have particular trouble with?

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    3. Not just determinacy, but the ability to grasp universals. Additionally, if panpsychism is not supplemented with something like substantial form, it cannot explain the unity of consciousness and thus it cannot even explain perception and imagination, let alone the intellect.

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  3. There seems to be an aspect to Aquinas’ account of sensation that does commit him to something like property dualism though.

    For Aquinas, when we sense an object, our sense organ takes on the form of the object in a non-physical way, else it would be the case that when I see a red-colored object my eye would literally become red, which is absurd.

    So given this, Aquinas would seem to accept the position of some philosophers of mind regarding the immateriality of sensation/experience.

    Now, Aquinas’ account of sensation is chaotic because it causes us to lose certain arguments for the immateriality of the intellect, such as the argument from abstraction.

    The reason for this is because IF it’s the case that our sense organs can take on a form without literally taking on properties of the form (my eye can see a stop sign without becoming red) then there’s no reason why our active intellects must take on properties of the universals that it abstracts.

    What I’m saying here is that IF my eye can take on the form of red without becoming red (because of spiritual immutation) my intellect can also grasp universals without becoming immaterial.

    What’s surprising here is that Aquinas didn’t see the contradiction between his account of sensation and his argument for the immateriality of the intellect.

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    1. I don't believe we need to take that hypothetical at all. Your contradiction seems to hinge on reifying an abstraction of "the intellect." But the soul is wholly present in every part of the body, although particular causal powers are localized in different parts. So what happens if sensation in humans is an aspect of our intellection?

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    2. My contradiction doesn’t hinge on that all.

      I’m not sure how much you know about Thomistic Psychology, but for Thomists, the intellect, the imagination, and the senses are distinct faculties with distinct operations. I’m simply arguing that Aquinas’ view of the operation of the senses leads us to lose that particular argument for the immateriality of the intellect (and by the way, the intellect isn’t an ‘abstraction’, it’s what continues after the death of the body).

      Also, to say that sensation is an ‘aspect’ of intellection is to make the common error of attributing to Aquinas a ‘Cartesian’ view of the soul (Descartes would say that the will, intellect, imagination, etc are aspects of the soul as opposed to distinct faculties). Ironically, that’s the point of this particular post.

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    3. Is this in the vein of the objection the Robert Pasnau makes against Aquinas's argument?

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    4. This objection comes from Daniel De Haan, a fellow Thomist.

      It’s not the same exact argument, but they bear a family resemblance.

      And no, I don’t think Dr. Feser addressed this particular objection sufficiently in his response to Pasnau.

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    5. Partial abstraction is not the same as complete abstraction. I don’t believe Aquinas would hold that the soul receives the form of red completely abstracted from any particularizing features. You are always receiving a kind of red and never redness itself. I believe that is the key difference that makes sensation essentially material.

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    6. I can only offer things as they seem to me, and that was as it seemed. My primary focus has been on the Angelic Doctor's metaphysics (and have been caught up in a number of other debates and concerns recently), although I did know that the imagination, senses, and intellect have different objects and so are distinct. But I don't see their distinction as problematic here: the human intellect depends on the senses and imagination to function under normal circumstances. So why can't the intellectual faculties 'subsume' (for lack of a better word) the sensual faculties, so that, in humans, to sense anything already involves the intellect? I don't claim to know, so I'm doing my best to be open to correction.

      Now, I think you've misunderstood me. I did not say that the intellect is per se an abstraction; I was talking about you abstracting one faculty, the capacity to receive forms in an intentional mode, from all the others.
      I also take issue with saying that I am attributing to St. Thomas one of Descartes' errors. The term aspect, at least in my experience, does not imply that they are not distinct powers in the soul.

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    7. Thanks for the comment, Scott.

      Maybe that is the case, but I’m not sure it helps.

      I also wouldn’t accept that Aquinas’ view committed him to believing that sensation was essentially material, I think there’s room for it being immaterial for him.

      Why can’t it be the case that we grasp the universal without taking on the properties of the universal?

      Surely our intellect takes on the ‘universality’ of the universal - so there is a sense where there is an identity of properties, but does this necessitate the thought also becoming immaterial? Spiritual immutation really seems problematic here.

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    8. Aquinas does not think that universals are things that have some property, universality. He thinks that we can think universally of things in the world in virtue of a universalizing mode of consideration, that is, a certain way of grasping the nature of a thing.

      Aquinas is not, in contemporary parlance, a realist about universals. He does not think that there is any thing actually common to, e.g., all men. Each man has his own human nature, and men constitute a species because their natures are formally identical; they are not numerically identical.


      What I’m saying here is that IF my eye can take on the form of red without becoming red (because of spiritual immutation) my intellect can also grasp universals without becoming immaterial.


      Since the intellect is not grasping things, universals, it is also not grasping things, universals, which have some property of immateriality. So Aquinas is not thinking that the intellect must be immaterial because it grasps immaterial things, and the case is not parallel to the idea of spiritual immutation.

      Aristotle understands perception generally as a kind of immaterial reception of forms, and he thinks that to immaterially receive a form a sense needs to lack that form altogether. So the eye must not be colored, if it is to receive color, its proper object. In De anima III.4, he applies this argument to intellect. As the object of sight is color, the object of intellect is corporeal being, so as the organ of sight, the eye, must be uncolored, the organ of intellect must be unbodied. That is to say, there cannot be any organ of intellect.

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    9. (There are also other arguments that, e.g., the universal mode of consideration would only be possible by that which is immaterial. And if some Thomists sometimes speak of "the grasping of universals," it may be shorthand for "the grasping of natures universally".)

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    10. (Naturally there is also a complication here in the idea that the object of the human intellect is corporeal being. For what of human thinking about, e.g., the soul or God? I think Aquinas's answer has to be that humans think in the primary case of material things, and when they start doing philosophy they rely on analogies and bend language in ways to reach a kind of provisional understanding of non-material things. But it is an extended and derivative use of language.)

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    11. Forms adhere in the senses in a different way than in the soul or intellect. While an intellect grasps the essential qualia of the form, the senses merely record that the form is there.

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  4. For Aquinas, when we sense an object, our sense organ takes on the form of the object

    Is that true, though? Is it not the intellect which receives the form, and not the sense organ, which senses only particulars?

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    1. I suppose it depends on where you think the power of perception resides. It might, though I'm not sure, be a bit Cartesian to say that the power of sensing resides in the intellect.

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    2. Well, yes. But my understanding has always been that sensing is of particulars, and thus can happen in the sense organs. But forms should be intellectual.

      However, the above comments make me think I was oversimplifying.

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    3. Now, immutation is of two kinds, one natural, the other spiritual. Natural immutation takes place by the form of the immuter being received according to its natural existence, into the thing immuted, as heat is received into the thing heated. Whereas spiritual immutation takes place by the form of the immuter being received, according to a spiritual mode of existence, into the thing immuted, as the form of color is received into the pupil which does not thereby become colored. Now, for the operation of the senses, a spiritual immutation is required, whereby an intention of the sensible form is effected in the sensile organ. Otherwise, if a natural immutation alone sufficed for the sense's action, all natural bodies would feel when they undergo alteration. (ST I q. 78 a. 3)

      Sensing is of particulars, but it is by way of forms--accidental forms, that is, for example of color and shape.

      Aquinas seems to think that what is seen, heard, etc., are colors, sounds, etc., and the perception of particulars involves the so-called interior senses (cf. a. 4). But the topic is a difficult one.

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  5. Read the article on Aquinas and the soul with my University's subscription to the database. And one question I have for those who hold the view that the substance of the human persists, while the substantial form is adhering in that: If what is (the substance that is) persisting is rationality, which as discussed is an immaterial kind of substance, isn't rationality supposed to adhere in the soul? Which is quite the opposite from the picture described above where the soul adheres in rationality.

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    1. Bill, I haven't read the article (no (free) access, sorry), so maybe I have it wrong, but: the substance can't be "rationality", because then it would be impossible for there to be TWO such substances who are rational beings, they would both be "rationality" and thus would be the same substance. In any such discussion, surely they would hold rather that the substance is rational, but not rationality?

      If I got my Thomism down correctly, (admittedly a real question), the proper Thomist view is that the soul of a human is the soul of a rational animal, and thus it takes existence ONLY by being the form of human body: it is nonsensical to conceive of the human soul being immaterial in the sense that it could have begun to exist apart from matter. Whatever else happens to it later, it can never escape or depart from having first been the form of informed matter, (specifically, the form of a human being enfleshed), and thus always retains a relation to determinate matter, and an orientation to be the soul of a living body. It is thus essentially different from the "immaterial" forms of angels, which do not have any relation tor orientation o determinate matter.

      Because the human being is a rational substance, a person, there is a subsistence that can persist after the separation of soul and body: the subsistence continues past death. But the substance is _defined_ in terms of a whole being, which is an integrated body and soul, not just a subsistence.

      I would say rationality inheres in the person in virtue of the immaterial soul, and that the person persists after death, and while this implies that the substantial form (the soul) persists after death, it does so remaining in relation to the body, i.e. as the soul of a determinate body.

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    2. What I was taking issue with was not that view but the view that Feser presented and if I understood him correctly it was that rationality was a highly diminished part of the substance of a human body. Which is distinct from the soul the form, which the soul adheres in upon death.

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  6. Hi Ed,

    Thanks for an interesting post. I would classify Aquinas as neither a substance dualist nor a property dualist, but as what I call an action dualist. That is, he holds that some of our actions are bodily actions, while others are non-bodily actions. Unlike property dualists, Aquinas does not hold that mental acts (or properties) supervene upon physical acts (or properties).

    By the way, the article by Gaven Kerr on Aquinas' Metaphysics in IEP states: "Within Aquinas’s metaphysical framework, substances can be both material (cats, dogs, humans) and immaterial (angels), but as noted above, the paradigm instances of substances are material substances, and the latter are composites of matter and form..."

    Incidentally, I'd be interested to know what you think of Bertrand Russell's neutral monism. It seems to be a fairly sensible position. Thoughts?

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    1. You can read Dr. Feser's coverage of neutral monism in his "Philosophy of Mind" (publised in 2006) starting on page 124.

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  7. Vincent,
    Ed did his doctoral dissertation on Russell's neutral monism, also examining what Hayek taught on that topic.

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    1. Thanks Tim. By the way, I found an online article by Dr. Michael Egnor summarizing Ed's main objections to neutral monism:

      https://evolutionnews.org/2013/12/scientism_and_b/

      It makes for interesting reading. However, I'm doubtful of Egnor's assertion that "Russell proposed that qualia are the ultimate substance of which everything is composed." I'd like to see a reference for that.

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  8. What? Aquinas was a property duelist? You mean he used to challenge men to a duel in order to gain their property? How terrible! :-)

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    1. Aristotle's Categories divides (a) substances (b) accidents and (c) parts of substances. If the question is "what is mind in relation to body" then Descartes says (a), naturalism says (b) and Thomas says that it is a (c) along with body, and constituting with the body a person.

      The word "property" as Analytic guys use it is vague and probably includes at least (b) and (c), and maybe even (a).
      But if the properties we're talking about are parts, it's strange to call Thomas "dualist". Could someone be a monist with respect to parts?

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  10. I'm an atheist, but we share an interest in philosophy of mind. I had to leave a comment to let you know how much I appreciated your succinct descriptions of those views in philosophy of mind. I wish I would've found this post before I wrapped up my series on panpsychism. Thanks again!

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