The Unintelligibility of Substance Dualism

Over at Siris Brandon offers some interesting criticism of my argument against substance dualism. He distinguishes two senses in which we may say that a theory is viable. In one sense we simply mean to be asking what reasons someone might have for believing in that kind of thing. In that sense a viable theory is one which there is reason to believe. In another sense we may be asking not what the reasons are to believe it but instead what the thing in question is in the first place.  A viable theory in this sense is one that can tell us what the thing is. Brandon then goes on to show that this distinction corresponds to a distinction between things that a problem for a theory and things that a problem within the theory. Brandon then goes on to argue that my complaint is not a problem for the theory that there are immaterial substances but is rather a problem within the theory of immaterial substances itself and so should be answered by more research into immaterial substance and not with a dismissal of the theory.

The picture that Brandon seems to have is this. We decide whether or not there are good theoretical/common sense reasons to believe that there are immaterial substances and if we decide that there are we then try to construct a theory of what they are. Naturally in doing so we do not know very much about the immaterial substances and so one of the projects of the theory is to say more about what they are. Given this it is a mistake to think that our lack of understanding about what immaterial substances are is any reason to think that they don’t exist.

I completely agree with the spirit of Brandon’s comments but I do not agree with his conclusions. First, to where I agree. We clearly must recognize the kind of distinction that Brandon draws. And while I disagree that there are any real reasons or evidence for immaterial substances I agree that if there were, or if one thought there were, one should then go on to try and give a theoretical account of what they are.

Let us be generous and grant that there are reasons to think that some kind of substance dualism is true. When we then ask what an immaterial substance is we get told that it is the immaterial substrate of thinking and consciousness and that it is not located in space-time as we know it. David Chalmers has offered one way of making sense of this in terms of the matrix, and I won’t rehash it here but it seems clear that this kind of move makes the immaterial substance material outside of the matrix and so isn’t really a threat. What else can we do? At this point we have no further ideas. All we can say is that it is an X we know not what which underlies thinking and consciousness. If the theory never progresses past this point then we may start to think that it is in trouble.

So, to take Brandon’s example of evolution in biology, people had proposed accounts that looked evolution-ish as far back as Democritus, who seemed to have proposed that life as we know it was built up over time from simpler parts but this was not the theory of evolution because he did not have the right mechanism (natural selection). If the theory of evolution had stayed at the level of “evolution is whatever it is that underlies speciation and isn’t God doing it” no one would care about it. So too if the best that substance dualism can do is to say that an “immaterial substance is whatever it is that underlies consciousness and thinking and isn’t physical” it seems uninteresting. One might think this shouldn’t be a problem because lots of theories have been like that in the past (gravity seems to be a notable one) but the problem is that  it has been this way since its inception and not one step forward has been taken in 3,000 years. The most significant advance, if one were to call it that, has been the post-Humean nonchalance to the issue of physical/non-physical causation. If all there is to causation is constant conjunction, and the non-physical events are constantly conjoined with the physical ones then voila! mind-body problem (dis)solved!!

The upshot then is that fleshing out the theory will ultimately shed some light on the reasons for believing it. If we seem in principle unable to advance in specifying what a immaterial substance is, and we have physicalist alternatives that are relatively well understood, substance dualism starts to look impossible and we seem to loose our reason to believe it, which will in turn cause us to re-evaluate the reasons we used to have for believing it.

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5 thoughts on “The Unintelligibility of Substance Dualism

  1. If the theory never progresses past this point then we may start to think that it is in trouble.

    This, I think, is where you start running into problems; it needs to be shown that there is good positive reason for this conclusion in particular. But this requires a very different sort of argument (one that need not be related to questions of intelligibility, although it may be). You give the reason for this in your evolution example: we need positive reason to think no further inquiry will provide promising results because we know that success of inquiry depends crucially on possessing the right conceptual apparatus and access to evidence. One of the side issues that arose when evolutionary theories began to be popular again in the nineteenth century was that prior evolutionary theories — Democritus et al — had been shown to be both dead ends and not very explanatory. But this was, as you say, for lack of an adequate way of conceptualizing the process (what we, somewhat misleadingly, sometimes call a mechanism). But, lo and behold, it turns out that there are evolutionary theories that both capture the basic intuitions of the ancient ones but avoid their obvious problems and provide greater explanatory value. And the example is apposite because there were early modern philosophers who argued that evolutionary approaches were ultimately unintelligible (Malebranche, e.g.). But such people were, again, conflating a research problem (however tough) with a problem for theoretical approaches of that sort. And thus I think your appeal to history makes the conflation yet again. Yes, fleshing out a theory will ultimately shed some light on the reasons for believing it; but relative intractability doesn’t automatically give reasons for disbelieving it, much less judging it unintelligible, or even problematic. Some problems are just hard; and, depending on how you individuate approaches, there are arguably cases of fruitful approaches seeming sterile for millenia due to lack of just the right conceptualization or source of evidence. Negative evidence does not suffice here; positive evidence is needed.

    Moreover, you are quickly going to run into parity problems; materialism about the mind is at least as old as dualism, and it’s possible to argue that it is even older, since dualism of any sort requires the combination of both an account of matter and a doubt of some sort about the ability of matter to think. And yet not only has it not managed to knock off dualism, many of the major discoveries that inform modern materialism were made by dualists working on dualistic projects — that’s how early neuroscience developed, you know, since materialists doing the work come late to the scene. Modern materialists are therefore piggybacking on discoveries that a dualist might argue were made only because dualism made it possible to study the brain as an organ of thought while at the same time allowing one to hold in abeyance any particular material notions about how thought could be related to neuron firings and synapse growth. I mean, after all, what could it even mean to say that thought consists of brain events? 😉 But, seriously, people were asking that sort of question of materialism long before you started asking it of dualism, so by your own reasoning, people would have been justified in the eighteenth century of dismissing materialism as unintelligible and unviable. Were they entirely right?

  2. Hi Brandon, thank for the comment! As usual very helpful.

    Let me start by asking if you think that your response works equally well against Plantinga’s argument against physicalism?

    In the original post what I was trying to do is point out that though we can make this kind of point against both theories dualism is worse off. This is because the central concept of the theory –immaterial substance– is either question beggingly equated with the mental or else completely unintelligible. In the case of physicalism there are many issues about what counts as physical but there are at least non-question begging exemplars. We can say that physical things are those that are postulated by science, or are whatever the “medium sized dry goods” around here turn out to be, etc (I realize that this would beg the question against the idealist but issues about idealism are orthogonal to the physicalism/dualism debate as I see it). The question then becomes “how can that think?” and that, as you note, is a research problem. But we can’t even do this with immaterial substances. The very concept of an immaterial substance is bankrupt once one removes mental properties. How is it even possible that an immaterial substance could instantiate properties of any sort? As far as I know no one has ever attempted to answer that question. Usually, in fact, it is denied that there is an answer to this question because the immaterial substance is constituted by the non-physical mental properties, or some such.

    You say, “many of the major discoveries that inform modern materialism were made by dualists working on dualistic projects “.

    I guess you were joking when you said this but taking it seriously for a moment I am not sure why this is an issue. Suppose that someone tried to defend Euclidean geometry as a correct account of our world spacial structure because the discovery of non-Euclidean geometry was facilitated by assuming that Euclidean geometry was correct…but seriously 🙂 we have made some progress in understanding material substance but we have made zero progress understanding immaterial substance. We have even made some progress understanding how a physical system could have primitive versions of the aboutness relation but we have made no progress understanding how this could happen in an immaterial substance. So, yes, I think it was more rational to think that substance dualism could be true before the invention of the computer. Now the pendulum has shifted. I agree that it may yet shift back but it will take more than lame arguments like Plantinga’s that will convince only those that are already true believers. What we need is some way to see how it could even in principle be possible that the mind could be an immaterial substance.

  3. Taking the second point first, it was only half-joking; what’s at issue is not truth but intelligibility; and yes, that Euclidean geometry played the role it did is a reasonably good reason to think that the claim “The universe is Euclidean” is intelligible.

    I don’t think I fully realized that you were trying to run a dilemma, so not everything I said may be fully applicable. But as far as the dilemma goes, on the question-begging side you are assuming that the relation between mental properties and substances that think is parallel under dualism and materialism, and I don’t think this is right. Both materialism and dualism start with the same two basic phenomena: material substance and thinking. Contentwise they are distinct — work has to be done to figure out how exactly they are related in the first place. So materialists have both elements of their theory at hand, but they need to do work to show that the one explains the other. But substance dualists start with the phenomenon of thinking, hold that there is something about it that can’t be explained materially, and thence conclude that what is thinking is not material in the way that prevents material substance from being thinking substances. That’s all there really is to the claim that thinking substance is immaterial. Since the purported inability of matter to think is the whole reason for positing the existence of immaterial substance, there’s really no issue about the relation of the two in the way that there is for materialism. The materialist needs a plausible account of how material substance can think; the dualist does not need a corresponding account of how immaterial substance can think but a plausible account of why material substance can’t (in order to motivate positing immaterial substance). And if the dualist has a good argument that material substances can’t think, then, since (1) we obviously do think; (2) but this thinking cannot be instantiated by a material substance; it follows that (3) the substance in which thinking is instantiated is not material. Since mental properties were the reason for postulating the immaterial substance in the first place, there’s no question-begging involved.

    On the other hand, now that I’ve learned that to interpret your original argument correctly, one needs to disentangle the two sides of the dilemma, it now makes a lot more sense where you were going with the claim about unintelligibility.

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