Normativism and Mental Causation by Justin Thomas Tiehen, B. A. Dissertation

Davidson thought that the key to accounting for mental causation was to identify mental and physical events. As his critics rightly noted, this by itself is not enough. For, not all of an event’s properties are causally efficacious. Still, it would be an overreaction to jump from this good point to the conclusion that just one of the properties possessed by a coarse-grained, Davidsonian event will be the causally efficacious one. Again, suppose that I strike a match causing it to light. The coarse-grained event that is the striking possesses many properties that are causally irrelevant to the lighting: that of occurring in the year 2007, that of occurring within the United States, that of being described by me here in this chapter, and so on. However, the striking also possesses many distinct properties that are all causally relevant to the lighting: that of being the striking of a match, that of being the striking of a dry match, that of being the striking of a match in the presence of oxygen, and so on.

Some of the striking’s causally efficacious properties are nested within others: being the striking of a match is in some sense included in being the striking of a dry match. Some of the striking’s causally efficacious properties merely share a common component without there being any such nesting: being the striking of a dry match and being the striking of a match in the presence of oxygen have something in common, but each property also possesses a feature the other lacks. And some of the striking’s causally efficacious properties are completely independent of one another: being the striking of a match and being something that occurs in the presence of oxygen have no feature in common.

The point translates over when we drop the Davidsonian conception of events in favor of the Kimian one. If events are fine-grained, then the striking of the match, the striking of the dry match, and the striking of the match in the presence of oxygen are all distinct events. Each of these events is causally relevant to the match’s lighting however. Now naively, the match’s being struck and its being struck and dry do not causally compete with one another. Relatedly, if we say that each event is causally relevant to the lighting, we do not seem to be committing ourselves to any easily recognizable form of causal overdetermination. And this is because causes generally operate only against certain background conditions. Striking a match can cause it to light, but only if certain background conditions obtain, including that the match is dry.²⁸³ Striking a dry match – that is, the match’s instantiation of the conjunctive property (being a struck match & being dry)²⁸⁴ – is a kind of composite event which brings cause and background condition together here. Rather than causally competing with one another, the events and properties in this case seem to entail one another’s positive causal status.

I believe that the relation between mental and physical properties is relevantly like the relation between the match’s property of being struck and its property of being struck and dry. Or more accurately (for reasons connected to my normativism about belief properties), I hold that it is relevantly like the relation between the match’s property of being struck and dry and its property of being struck and in the presence of oxygen. The analogy is not perfect, as we will see. But, I think it works well enough. Just as there is no causal competition in the match case, so too there is no causal competition between mental and physical properties, I claim. Thus, the solution to the causal exclusion problem which I set out in this chapter involves rejecting (Competition). Before we get to my proposed solution, and before we see how it applies to my own particular brand of antireductionism about the mental, we will first need to lay a bit of groundwork.

8.1 A Shoemakeresque View

In this section I set out what I will be calling a Shoemakeresque view. The Shoemakeresque view combines a reductive form of causal structuralism together with a version of the subset view of realization. The view is Shoemakeresque in the sense that it resembles Sydney Shoemaker’s own view in important respects. However, it decidedly is not Shoemaker’s own view. It includes some elements that Shoemaker himself explicitly rejects, and gives an unconventional gloss on other elements that he would accept. It also is not necessarily a view I would recommend Shoemaker to accept. My primary reason for discussing the Shoemakeresque view at the length I do is not because I think it’s true – in fact, I reject each of its two components – but rather because it sets up an especially clear view of what a nonreductive physicalist solution to the causal exclusion problem might look like. Later on, we will consider how a philosopher who rejects the Shoemakeresque view may be able nevertheless to incorporate into her own position the account of mental causation that the view makes available.

9.1.1 REDUCTIVE CAUSAL STRUCTURALISM²⁸⁵

It is uncontroversial that (at least many) natural properties bestow causal powers on their instantiations. The property of being copper, for instance, bestows on its instantiations the power to reflect reddish light waves (while absorbing other light waves), the power to conduct electricity extremely efficiently, the power to boil at 2835 K, and so on. The complete set of causal powers that a natural property bestows on its instantiations is what I have been calling that property’s causal profile in this work. So then, what is uncontroversial is that (at least many) natural properties have causal profiles in the sense described. What is controversial is the precise nature of the relation between natural properties and their causal profiles.

At one end of the spectrum there are those like Lewis who take the relation to be thoroughly contingent.²⁸⁶ On this view, there are possible worlds governed by different causal laws at which natural properties like copper possess causal profiles other than the ones they actually possess. So for instance, there are worlds where copper possesses the very causal profile that sulfur possesses here in the actual world, and so where copper is yellowish in color rather than reddish, a poor conductor of electricity rather than a good one, boils at the much lower temperature of 717.8 K, and so on. At such worlds, copper behaves indiscernibly from the way sulfur behaves here in the actual world. If (per impossibile) one were given both a sample of this-worldly sulfur and a sample of other-worldly copper, one could not tell the difference between the two.

At the other end of the spectrum there are causal structuralists like Shoemaker who hold that a natural property’s essence is in some sense wholly constituted by its causal profile, and thus that the relation between natural properties and their causal profiles is necessary rather than contingent.²⁸⁷ According to causal structuralists, a natural property is as it does (or at least, as it is capable of doing). On this view, there will be no worlds where copper behaves just as sulfur actually does. If some property P possesses the same causal profile at a world w that sulfur possesses here in the actual world, then P just is sulfur. For the purpose of setting up my favored solution to the causal exclusion problem, it is causal structuralist views that I want to focus on.

Now among causal structuralists there is room for disagreement as to whether natural properties can be, in some sense, reduced to their causal profiles. Typically when we specify a causal power of some natural property, we invoke some other natural property. So for instance, we might say that the property P possesses the power to cause Q instantiations, thereby mentioning Q in our specification of P’s power. A causal structuralist might think that this sort of reference to natural properties in the specification of causal power is ineliminable. If so, she will deny that natural properties generally can be non-circularly reduced to their causal profiles. Such a causal structuralist might regard natural properties and causal powers as equally basic but mutually dependent metaphysical notions. In his more recent writings, Shoemaker seems to be defending a view along these lines.²⁸⁸

Alternatively, a causal structuralist might think that though we typically refer to natural properties while specifying causal powers, this reference is eliminable. In his paper “Causal Structuralism,” John Hawthorne describes how one might try to use the method of Ramsification to eliminate such reference.²⁸⁹ Instead of Ramsifying folk psychology (or some other specifying psychological theory) as causal functionalists in the philosophy of mind do, one could instead Ramsify a “lawbook,” a theory conjoining all the causal laws of a world. Just as Ramsification promises to allow functionalists in the philosophy of mind to avoid circularity in their proposed analyses of mental states in terms of causal inputs and outputs, perhaps Ramsification will allow causal structuralists to avoid circularity in analyzing natural properties in terms of causal powers.

Call the view that proposes to analyze natural properties in this way reductive causal structuralism. According to reductive causal structuralists, natural properties are nothing over and above clusters or sets of causal powers. So for instance, all there is to a thing’s being made of copper is its having the power to reflect reddish light, to conduct electricity efficiently, to melt at 2735 K, and so on. In his earliest articulation of his view, there are points at which Shoemaker seems to be embracing reductive causal structuralism of this sort.²⁹⁰

Reductive causal structuralism provides a kind of simplicity that nonreductive causal structuralism does not. Given that my interest here is primarily to set up my favored solution to the causal exclusion problem, and not to defend any very specific view about the nature of properties, this simplicity wins the day. In what follows then let’s provisionally assume the truth of reductive causal structuralism.

9.1.2 CAUSAL POWERS: TYPES AND TOKENS

Now, what exactly are the causal powers that comprise causal profiles? Though I have been speaking of causal powers throughout this work, I have yet to provide an account of them. Causal powers seem to admit of type/token distinctions. In the billiard room there is both a candlestick and a revolver. Both of these objects possess the power to kill a person, but in the murder of Mr. Body, it was the candlestick’s power that was exercised, not the revolver’s. Given this type/token distinction, we can think of causal powers simply as properties and their instantiations.

In saying that causal power types are properties, I do not mean to be suggesting that they are natural properties. If they were, then there would be no hope of reducing natural properties to their causal profiles, and reductive causal structuralism really would be circular. Instead, causal power types should be viewed as a separate though still metaphysically interesting set of properties. Circularity is thus avoided. Now, allowing that there are properties that are metaphysically significant without being natural might initially seem more problematic or at least unconventional than it really is. It isn’t really though. To show this, consider the following verbal variant of the present view.

According to this variant, the set of natural properties is somewhat larger than is often thought. In addition to the traditional natural properties – things like copper, or firing C-fibers, or being an electron – there are certain untraditional natural properties – namely, causal power types. These untraditional natural properties are just as natural as traditional natural properties are. What makes them untraditional is just that philosophers have not as widely thought of them as natural properties. Given this setup, reductive causal structuralism can be reinterpreted as the view that all traditional natural properties can be non-circularly analyzed in terms of untraditional natural properties.

What this is meant to show is that in entertaining reductive causal structuralism, we need not think of ourselves as positing entities of some radically new sort. Instead, we should think of causal powers as being the exact same sorts of entities with which we are already familiar. In the discussion that follows I will reserve the term ‘natural properties’ for traditional natural properties, not applying it to causal power types. This is done solely for the purpose of minimizing confusion.

9.1.3 CONJUNCTIVE PROPERTIES AND COMPOSITE EVENTS

Once we appreciate that causal powers are just properties and their instantiations, a certain analysis of (traditional) natural properties suggests itself. We can think of all natural properties as being conjunctive in nature, where their individual property conjuncts are the causal power types that make up their causal profiles. So for instance, copper can be identified with the following conjunctive property: (the power to reflect red light & the power to conduct electricity efficiently & the power to boil at 2835 K & etc.). By extension, an instantiation of copper can be thought of as a conjunctive, or better, a composite event, whose parts are tokens of these causal power types.²⁹¹

Again, it is uncontroversial that (at least many) natural properties bestow causal powers on their instantiations. The analysis just proposed offers a way of explaining what this bestowal relation amounts to exactly. According to the analysis, a natural property “bestows” causal powers on its instantiations in the sense that a natural property just is a conjunction of causal power types, and thus its instantiations just are composite events having causal power tokens as parts. A good portion of the discussion that follows will be devoted to making moves of this sort. That is, to taking some relatively widely accepted philosophical claim, and working out how exactly that claim should be understood on the Shoemakeresque view.

9.1.4 THE SUBSET VIEW OF REALIZATION

While continuing to assume the truth of reductive causal structuralism, I now want to develop a variant on Shoemaker’s subset view of the realization relation. Let’s begin by defining realization as a relation that obtains between natural property instantiations. Specifically, let’s say that a natural property instantiation e realizes a natural property instantiation e* just in case the set of causal power tokens that compose e* is a proper subset of the set of causal power tokens that compose e.²⁹² This entails that if e realizes e*, then e* will be a proper part of e.²⁹³ A war metaphor may be helpful here. The relation between e and e* is relevantly like the relation between World War II and the Battle of the Bulge. Both the war and the battle are events that are composed of small-scale skirmishes (further events), which are relevantly like token causal powers. The set of skirmishes that compose the Battle of the Bulge is a proper subset of the set of skirmishes that compose the whole war itself. From this it follows that the Battle of the Bulge is a proper part of World War II. The war is like the realizer, the battle is like the realizee.

Let’s now derivatively define a realization relation that obtains between natural properties themselves. Specifically, let’s say that a property P realizes a property P* just in case, necessarily, every P instantiation realizes a P* instantiation.²⁹⁴ P* is then multiply realized just in case it is realized by more than one property. This account of realization and multiple realization entails that the causal profile of a multiply realizable property will be (i) a proper subset of the causal profiles of each of its realizers, and (ii) a not necessarily proper subset of the intersection of the causal profiles of its realizers.

To see the subset view of realization in action, let’s return to pain and suppose that it has five different physical realizers, one found in human beings, one in Martians, one in Venusians, one in Jupiterians, and one in Mercurians. Now, take the following five sets of causal power types to be these physical properties’ causal profiles.

P_H: {a, b, c, d, e, f, g, h}

P_M: {a, b, c, d, e, i, j, k}

P_V: {a, b, c, d, f, i, n, n}

P_J: {a, b, c, d, k, n, o, r}

P_Me: {a, b, c, d, j, m, s, u}
The intersection of these five sets is the set {a, b, c, d}. These are the causal power types that belong to the causal profiles of each of pain’s physical realizers. To inject some concreteness into the discussion, think of these causal power types as being things like the power to cause wincing, the power to cause sobbing, the power to cause teeth-gnashing, and so on. The subset view of realization entails that pain’s causal profile is a not necessarily proper subset of {a, b, c, d}. Let’s suppose that pain’s causal profile just is this set itself (the subset is improper in this case). Then given reductive causal structuralism, or more specifically given the analysis of natural properties provided in subsection 9.1.3, it follows that pain can be identified with the conjunctive property (a & b & c & d). More concretely, it follows that pain can be identified with the following conjunction of causal power types: (the power to cause wincing & the power to cause sobbing & the power to cause teeth-gnashing & etc.).

The symmetric difference of the causal profiles of the five different physical realizers of pain is the set {e, f, g, h, i, j, k, l, m, n, o, p, q, r}. This is the set of causal power types that belong to some but not all of the causal profiles of pain’s physical realizers. Members of this set will include causal power types like the following, which we can suppose all belong to firing C-fibers’ causal profile: the power to exert a certain gravitational force on the planet Neptune, the power to reflect light of a certain wavelength, the power to cause various neural events, and so on. These causal power types will not belong to the causal profiles of those physical realizers of pain that differ somewhat from firing C-fibers in terms of mass, color, or ability to appropriately interact with neural events.²⁹⁵ The subset view of realization entails that causal power types of these sorts will not belong to pain’s causal profile itself. This result is not prima facie implausible. Most dualists think that pains exert no gravitational force on Neptune. The present account promises to offer physicalists a way to accept this view as well.

9.1.5 TRADITIONAL CONJUNCTIVE PROPERTIES AND REALIZAITON

Again, given reductive causal structuralism we can identify pain with the conjunctive property (a & b & c & d). The physical properties that realize pain will then be broader conjunctive properties that take pain as one of their conjuncts. So for instance, given its causal profile we can identify P_H with the conjunctive property (a & b & c & d & e & f & g & h), which is equivalent to (pain & e & f & g & h). Similarly, P_M can be identified with the conjunctive property (pain & e & i & j & k). This provides us with a partial explanation of the supervenience of mental properties on physical properties. Why do all beings who instantiate P_H instantiate pain? For the same reason that all beings who instantiate (P & Q) instantiate P. This is about as far from treating supervenience relations as primitive as one can possibly get, and so there seems to be little threat of running afoul of superdupervenience here.²⁹⁶

Recall that in a passage cited back in Chapter 8, Yablo described as “deliberately farfetched” the idea that physical properties are conjunctions with mental properties as conjuncts.²⁹⁷ Similarly, Shoemaker considers and rejects the though. There is far less difference between these authors’ views and present proposal than it might initially seem however. For let Shoemaker explain why he rejects the conjunctive view.

A realizer of the property of being in pain cannot be being in pain and being F for some F. And that goes with the fact that not every subset of a property’s causal features defines a property having just that set of causal features. To put it in another way, not every subset of the conditional powers conferred by a property is such that there is a property that confers just that subset.²⁹⁸

On analogy to the distinction between traditional and untraditional natural properties which we briefly considered back in subsection 9.1.2, let’s say that a natural property is a traditional conjunctive property just in case (i) it is a conjunctive property, and (ii) it can be decomposed into conjuncts, each of which is a natural property. An untraditional conjunctive property, then, is a property that satisfies (i) but not (ii). Traditional conjunctive properties are meant to be just what they sound like. They are those natural properties that philosophers traditionally regard as conjunctive, like (being red & being round). Now suppose that, persuaded by the above passage from Shoemaker, we deny that every conjunction of causal power types is identical to some natural property. Then, even as we embrace the conjunctive proposal and hold that every natural property is conjunctive, we will be deny that every natural property is a traditional conjunctive property.

Take copper for instance. According to the conjunctive proposal, copper is identical to the conjunctive property (the power to reflect red light & the power to conduct electricity efficiently & the power to boil at 2835 K & etc.). If this conjunctive property cannot be decomposed into conjuncts in such a way that each of those conjuncts is itself a natural property, it will then follow that copper is not a traditional conjunctive property. Rather, it will be an untraditional conjunctive property.

With this distinction between traditional and untraditional conjunctive properties in hand, let’s now return to the realization relation that obtains between natural properties. According to the view we are presently considering, P_H is identical to the conjunctive property (pain & e & f & g & h). Now, pain is a natural property. Suppose, though, that (e & f & g & h) is not identical to some natural property, nor can it be decomposed into conjuncts each of which is a natural property. Suppose also that this is how things generally go for pain’s physical realizers. Then following Shoemaker we will be able to say that no physical realizer of pain is identical to pain and F, for some natural property F. Rather, each physical realizer of pain will be identical to pain and G, for some conjunction of causal powers G that is neither a natural property itself nor decomposable into natural properties. In other words, even though pain’s physical realizers are conjunctive properties having pain as one of their conjuncts, they are not traditional conjunctive properties. Instead, they are untraditional conjunctive properties.

Now, Shoemaker builds non-conjunctiveness into his own account of realization as a relation between natural properties.²⁹⁹ If we wanted to do so, we could follow his lead on this point by developing an account of traditional realization and traditional multiple realization. Such an account would build traditional non-conjunctiveness into the very notions of traditional realization and multiple realization. However, nothing of real value would be obtained by going to the trouble of doing so. Things will be kept simplest if we leave traditional conjunctive properties and traditional realization and multiple realization to the side. The point of touching on the issue at all is that to the extent that Yablo and Shoemaker are getting at something important when they distinguish the realization relation from the relation between a conjunctive property and its conjuncts, it seems that we can get at essentially the same point on the present account, even as we take realizing properties to be (untraditional) conjunctions having realized properties as conjuncts.

9.1.6 CONCLUSION: THE METAPHYSICAL PICTURE

Before turning to see how mental causation works on the Shoemakeresque view we have now set up, let’s pause to make sure we have fully taken this view in. We might think of the world as follows. At the most basic level, there are objects, there are the causal powers objects possess (instantiate), and there are facts about how causal powers tend to cluster together (about how they are coinstantiated). So for instance, in connection with the Shoemaker claim considered in the previous subsection, perhaps it is a fact that while a number of objects possess all of the causal powers from the set {a, b, c, d, e, f, g, h} few or no objects possess just the causal powers e-h without also possessing the causal powers a-d. If so, this would be in effect a fact about the natural properties pain and P_H.

Groups of causal powers tend to travel together, like groups of friends. The causal powers e-h are like friends of friends who are not really friends themselves. Such people might travel together, but probably only if their mutual friends travel along with them – that is, only if people relevantly like the causal powers a-d are traveling as well. To push the metaphor further, imagine a married couple who sometimes travels with one group of friends, and sometimes travels with a different group of friends. This is relevantly like multiple realization according to the Shoemakeresque view. Sometimes the causal powers a-d travel with the causal powers e-h, sometimes they travel with the causal powers e, i, j, and k, and sometimes they travel with yet other groups of causal powers. That is just to say, sometimes pains are realized by P_H instantiations, sometimes they are realized by P_M instantiations, and sometimes they are realized by the instantiations of yet other physical properties.

As we touched on back in Chapter 7, nonreductive physicalists often hold that there are patterns – true generalizations – at many different levels of nature. Typically, these different levels are pictured as being arranged vertically, so that the mental level is above the biological level, which in turn is above the chemical level, which in turn is above the physical level. On the Shoemakeresque view, though, it is more natural to picture the levels of nature as being nested within in one another, like Russian matryoshka dolls. The physical level is “thicker” than the mental level, not “beneath” it. Nested as opposed to vertical levels actually seems to fit better with claims occasionally voiced by nonreductive physicalists to the effect that mental properties (and “higher” level properties generally) are more abstract than physical properties. If you take a physical realizer of pain, like P_H, and abstract away from it the right causal power types, like the types e-h, you will be left with the property of pain itself.

The Shoemakeresque view seems to help with the outstanding problem we were left with back in Chapter 7. Recall that the worry there was that though a nonreductive physicalist who believes in natural and multiply realizable properties may be able to avoid treating the truth of a generalization like (3) as a coincidence, it seems that she might be forced to treat the a generalization like (3’) as one.

(3): Both human pains and Martian pains, when of a certain duration and intensity, typically cause hair loss.

(3’): Both P_H instantiations and P_M instantiations, when of a certain duration and intensity, typically cause hair loss.

If P_H and P_M are conjunctive properties, though, which both include pain as one of their property conjuncts, then this would seem to go some way toward explaining the truth of (3’). That P_H instantiations and P_M instantiations behave similarly in various ways would be explained by the fact that both conjunctive properties include within themselves as conjuncts the same natural property pain. Analogously, the fact that red circles and red triangles behave similarly in various ways is explained by the inclusion of the property of being red in each of the conjunctive properties, (being red & being round) and (being red & being triangular). No explanation of this sort appears to be available to the reductionist, and so the Shoemakeresque view promises to sustain the nonreductive physicalist’s alleged advantage.