Did the Council of Vienne Rule Out Substance Dualism?

I recently received a message from a reader, asking whether the Council of Vienne rules out the view in philosophy of mind known as "substance dualism." According to substance dualism, the soul is an incorporeal substance which can exist separately from the body. Famously, a version of substance dualism was held to by Descartes.

I thought the response I wrote might be of interest and help to some readers. I would argue that, whatever other issues one might have with substance dualism, this position is not ruled out dogmatically. (This is not to say that I endorse the position or that I even consider it reasonable, of course.)

The ratified decree of the Council of Vienne, promulgated by the Apostolic See, says this:

Moreover, with the approval of the said council, we reject as erroneous and contrary to the truth of the catholic faith every doctrine or proposition rashly asserting that the substance of the rational or intellectual soul is not of itself and essentially the form of the human body, or casting doubt on this matter. In order that all may know the truth of the faith in its purity and all error may be excluded, we define that anyone who presumes henceforth to assert defend or hold stubbornly that the rational or intellectual soul is not the form of the human body of itself and essentially, is to be considered a heretic.

Here is the answer I gave to the questioner, which I've adapted from our exchange:

"It has been a while since I investigated this, but yes, I was pretty convinced at the time that the condemnation does not rule out substance dualism. Here are a few reasons:

1) The text itself just says that the intellectual soul is per se and essentially the [substantial] form of the human body. That's what it says. That statement is not equivalent to the statement that a substantial form cannot be a substance. Someone might personally think that follows, because of a certain metaphysics of substantial forms. But the Council itself does not assert that.

(Incidentally, as far as the metaphysics goes, Aristotle himself says that the form is a substance, in Metaphysics. The interpretation of these texts is quite convoluted of course, but it's clearly there. I'm not saying Aristotle was a substance dualist, of course.)

Perceptual Representation: Pictures and Sounds, Seeing and Hearing

Perceptions are representations. What representations are can be cashed out in several ways.

First, they are about something.

Second, they represent the world as being a certain way.

Moreover, they have satisfication notions associated with them (and corresponding satisfication conditions, i.e., conditions that must obtain for them to be satisfied). The satisfaction notion of desires is 'being fulfilled' or not; with belief it is 'being true' or not; with volitions it is 'being done' or not; with commands it is 'being obeyed' or not; and with perceptions it is 'being accurate' or not.

Representations include words, sentences, beliefs, pictures, questions, paintings, videos, signs, diagrams, maps, hand gestures, commands, recordings, desires, and, in the case at hand, perceptions.

If a given representation has a satisfaction notion associated with it, it will also follow that it has satisfaction conditions. Giving the satisfaction conditions for a type of representation is (at least part of) giving a semantics for that type of representation.

Much work has been done on giving semantics for various sorts of linguistic representations. Whole classes of sentences have been given rigorous semantics. For instance, famously, modal language has been given a whole semantic theory, rigorously formulated in terms of mathematical models involving possible worlds.

Arguably, something similar can be done for pictures.

If a rigorous semantics can be given for pictures, this may hold some promise for giving a rigorous semantics for visual perceptions. Naively, we think of vision as giving us an "image". Think for instance of Ernst Mach's drawing of his own visual field:

Mach's picture of the visual field

With appropriate modifications for the perspective and particularities of our visual field, the naive application of pictorial semantics to visual-perceptual semantics would be to straightforwardly give the same semantics for our visual perceptions as we would for a drawing of our visual field.

This is obviously simplifying hugely and leaves a host of questions unanswered. But it allows us to get a preliminary grip on things.

What I'm interested in lately is whether, suitably modified, the semantics of auditory perception will be similar to the semantics of visual perception.

You can think of visual perception as giving you a picture, where the picture includes such properties as {OBJECT, SHAPE, MOTION, COLOR, DISTANCE, SPACE, TEXTURE, CAUSE, AGENCY}. All of these properties are represented in visual perception (and, with most of them, in pictures too, at least generally).

(Note: One of the simplifications we have to make in assuming the semantics of visual perception is just like the semantics of pictures is that, as with the semantics of pictures, visual perceptions do not have a temporal-duration aspect: A good assumption for pictures maybe, which can be thought of as "instantaneous" in some way; on the other hand, a bad assumption for visual perception, which as perceptual psychology demonstrates represents motion, and an even worse assumption for auditory perception.)

So we can think of vision as giving a picture. Can we think of hearing as giving us a picture too? If we can, then if the move from pictorial semantics to visual-perceptual semantics is relatively straightforward, then so will the move be from pictorial semantics to auditory-perceptual semantics (and maybe we can even find a better representational correlate than pictures for sound; hint: recordings maybe?).

Well, clearly, hearing doesn't immediately represent all of the same properties as vision. And neither does vision represent all of the same properties as hearing.

However, that doesn't need to stop us from thinking of hearing as presenting an auditory "picture," at least if we understand "picture" as picking out a general representational structure that is in some way common to normal, physical pictures and our mental, visual images. After all, as we said before, we can think of the visual image as a picture representing such properties as {OBJECT, SHAPE, LOCATION, MOTION, CHANGE, COLOR, DISTANCE, SPACE, TEXTURE, CAUSE, AGENCY}. But then maybe we can also think of hearing as giving us an auditory representation, structurally similar to the visual image, but instead representing such features as {OBJECT, LOCATION, MOTION, CHANGE, DISTANCE, SPACE, CAUSE, VOLUME, PITCH, TIMBRE}. We might even be able to include SHAPE and AGENCY in there in some cases (almost certainly in the case of bats), though I'd have to double-check the scientific literature.

In other words, the perceptual "structure" could remain the same between visual perception and auditory perception, and indeed, some of the qualities that are represented in vision may be represented in hearing, and vice versa. For instance, just from what I've listed, the intersection of properties represented in hearing and vision will include such features as {OBJECT, LOCATION, MOTION, CHANGE, DISTANCE, SPACE, CAUSE). On the other hand, maybe it is unique to vision to include {COLOR, TEXTURE}, and maybe it is unique to hearing to include {VOLUME, PITCH, TIMBRE}.

But again, despite the differences in features that are represented in hearing and vision, the overall representational structure might be, generically, the same at a certain level of abstraction.

What would be interesting would be to work out a precise semantics for visual perceptions and a precise semantics for auditory perceptions and see where, in the details, the two actually differ. Obviously hearing and vision will have their accuracy conditions assigned by different systems of depiction. But it's exciting to think that the two might not be so far apart, that they may, structurally speaking, having a lot in common, and that light might be shed on both by looking at conventional, physical representations (such as pictures, recordings, etc.).

Lowe, Mental Causation and Laws of Nature

E.J. Lowe has an interesting theory of dualistic mental causation. He proposes a model where mental causation doesn't happen by mental events directly causing particular physical events. Instead the mental exerts its influence by explaining the existence of the entire neural causal chain leading to physical movement.

Suppose you have a series S of neural events in the actual world which lead to a physical movement P. Given Lowe's view that the mind does not directly cause any neural event there must be an external physical event E which causes the first event in the neural chain. So it'll look something like this:

• S: E > (N1 > N2 > ... > Nn) > P

Suppose Lowe is right and mental events do not directly cause any particular neural event, but instead explain why this whole series of neural events exists instead of another. For comparison, Lowe proposes that the mind acts in the same way that God could act as sustainer of the universe. Suppose the universe is an infinite series of physical events where God doesn't directly cause any of the events in the series:

• U: ... > P0 > P1 > P2 > ...

Now, every event in the series has a physical cause within the series, but there is still the question about why it is U which exists in the first place as opposed to another, distinct, series (say U*):

• U*: ... > P0* > P1* > P2* > ...

On this picture God does not directly cause any particular physical event in U, but rather explains why this whole series of physical events exists in the first place. Here God sustains the universe, as opposed to interacting with it.

If the mind's influence on the body is like this, then the mind would have to have counterfactual control over which series of events occurs given E. In other words, if the mind had decided differently, then had E happened a different chain of neural events would have existed than S.

Now presumably one chain of events is identical to another if all the events in the one chain are identical to the corresponding events in the other. Somewhat more precisely:

• (E1 > E2 > ... > Em) = (E1* > E2* > ... > Em*) if and only if (a) E1 = E1* and E2 = E2* and ... and Em = Em*; and (b) Ei > Ei+1 if and only if Ei* > Ei+1* for 1 < i < m

Obviously an identity criterion for infinite causal chains would be pretty easy to give too, but we're dealing with causal chains in the brain which lead to physical movement, so presumably this is unnecessary for our purposes. If you like you can think of this criterion as being restricted to causal chains in the brain.

Now then, suppose the mind does cause a different chain than the actual one. Call this chain S*. In order for a different causal chain to happen than the actual one it'd have to look something like this (for convenience I put the original chain above the new one):

• S: E > (N1 > N2 > ... > Nn) > P 
• S*: E _ (N1* > N2* > ... > Nm*) _ P with Ni =/= Ni* for some i, 1≤ i ≤ n

The reason there must exist an i such that Ni =/= Ni* is because of our identity criterion above. If all the corresponding events in the chains are identical then the chains themselves are identical. But we supposed that some different chain was brought about, which again is possible given Lowe's view, since Lowe's view implies the mind has counterfactual control over which series of events occurs given E.

I leave blanks in between E and N1* and between Nm* and P since we don't want to assume too much; maybe the mind will cause a chain to exist which is uncaused or which does not lead to the same physical movement P. Now, there are a few possibilities here.

(i) If E does not cause N1* then a law of nature is violated, since (in the actual world) it is a law that E will cause N1. (Actually, if I were being more precise a bit more detail and argument would be necessary here, but this is right.)

(ii) If E does cause N1* and N1 =/= N1* then a law of nature is violated, since it is a law that E will cause N1. Moreover, the laws of nature are changed, since E causes something else than it normally would.

(iii) If E does cause N1* and N1 = N1* then no law of nature is violated yet, and we must look for the smallest i in the chain such that Ni =/= Ni*.

(iv) Again, such an i exists because of our identity criterion and the assumption of a different series S*. So Ni =/= Ni*. Then it will follow that Ni-1 = Ni-1*. So Ni-1 does not cause Ni. So a law of nature is violated, since it is a law that Ni-l will cause Ni.

Moreover, Ni-1 must cause Ni*, since this is a chain of neural events leading to a physical movement. By a metaphysically motivated syntactic rule for these representations of causal chains, there must be a '>' between every node in the chain. (If there were causal 'gaps' how could you really call it a causal chain; the only real causal chains would be the ones before and after the 'gap'.) So that means a law of nature is changed, since Ni-1 causes something different than it normally would.

So, no matter what, if the mind ever exercises the power it has to bring about another neural causal series, a law of nature must be violated. Moreover, if the first event in this series is caused then the laws of nature must be changed by the mind at some point. This is bad.

However, there's more to say than just that it's bad. Lowe could reply that, in the actual world, there are psychophysical laws which hold and which tell us the mind never actually uses this power of counterfactual control over laws. Thus, the normal patterns of events we observe still obey the laws of nature. The laws of nature continue to hold in this world.

But that leaves two options: (1) Does that mean minds never actually do anything? Are they causally effete and just let the world stay its course? Or else (2) Do minds still do something, and thereby contribute some causal influence? If they do, does that mean they cause the actual laws of nature to hold in the case of neural causal chains?

Both possibilities seem weird and unpalatable. If the first view is true that means mental causation never actually occurs in this world, though it could. On the second view there are two possibilities: Either (A) mental causation is superfluous, or else (B) laws of nature are really really weird.

On the one hand, it could be that the laws of nature by themselves are enough to explain why each event in the series causes the next, in which case the mental decision is superfluous and just 'backs up' the law of nature by its influence. The mind gives the laws of nature more 'oomph', though they are completely sufficient even without this 'oomph' at all. This would be case (A).

On the other hand, it could be that, once we move from E to N1, all of a sudden the mind is needed to hold up the laws of nature from then on. This is option (B). And that seems weird. That would mean when the brain comes into play, all of a sudden the laws of nature by themselves aren't sufficient for producing later events and the influence of the mind is needed to 'keep them going'. When it comes to the brain, the laws of nature need crutches; the mind is a metaphysical crutch. This is very metaphorical of course, but the point could certainly be made more precisely.

To be fair, this theory can't be disproven by the science. Neither option (1) nor (2) above is even possibly ruled out by the actual scientific evidence. So maybe this is one way to reject causal completeness while holding a theory that is empirically equivalent. I'm not sure it's a plausible one though.