Another stab at Swinburne's argument for dualism. I don't think the introduction of the notion of an informative rigid designator is at all helpful. Here's why.
Swinburne has a new argument for property dualism. If successful, the argument would seem to show that many familiar forms of physicalism are false. I don’t think the argument is successful.
The Anti-Physicalist Argument
To understand his argument, we need to understand some of Swinburne’s machinery. Swinburne introduces the notion of an informative rigid designator (IRD) to help introduce identity criteria for properties. On his view of property identity, properties are individuated by the IRDs that pick them out (2013: 24). Whereas a rigid designator will designate the same thing in every possible world (where it designates anything at all), an IRD is such that one who grasps its meaning will know what something has to be to be designated by that designator:
For a rigid designator … to be an informative rigid designator it must be the case that anyone who knows what the word means … knows a certain set of conditions necessary and sufficient (in any possible world) for a thing to be that thing (whether or not he can state those conditions in words) (2013: 12).
To use a well worn example, think about ‘lightning’ and ‘electrical discharge’. If it is true that lightning is just electrical discharge, we might expect that it is necessarily the case that lightning is electrical discharge. The expressions seem to rigidly designate the same thing and so there is no possible world in which it’s false that lightning is electrical discharge. While someone might grasp fully the meaning of lightning without being in a position to say anything at all about electrical discharge (e.g., speakers who were ignorant of the relevant scientific discoveries and had no concept of electricity), one might think that someone who knows what ‘electrical discharge’ means knows what it would take for something to be an electrical discharge and see that lightning fits the bill.
Let me note two interesting (apparent) consequences of this approach. The first is that an identity sentence involving a pair of IRDs is not simply necessarily true if true but logically necessary if true. The denial of the sentence would entail a contradiction (2013: 19). The second is that any identity sentence involving a pair of IRDs will be knowable apriori if true (2013: 24). Thus, if it is not apriori that a pair of IRDs designate the same thing, it is supposed to be necessarily false that they designate the same thing. The sentence that asserts that they designate the same thing would entail a contradiction.
With this much in place, there is a quick argument against the identification of any mental property with any physical property. To show that mental properties are distinct from any and all physical properties, Swinburne argues that it is not apriori that the IRDs that designate the physical properties or the mental properties designate the mental properties or the physical properties:
Since the informative designators of any physical properties are not logically equivalent to those of any mental properties (since there are different criteria for applying the designators), no mental property is identical to a physical property. The criteria for being in pain are not the same as the criteria for having some brain property … The criteria for being in pain are how the subject feels, and the criteria for brain and behavioural events are what anyone could perceive (2013: 70).
The argument is quick, but is it effective? I fear that there are two notions of IRD at play in his discussion. Once we’re clear on what they are, we shall see that his argument is no more persuasive than familiar unpersuasive conceivability arguments against physicalism that don’t make use of his notion of an IRD.
Evaluating the Argument
In the passage quoted earlier, Swinburne suggested that a speaker who knows the meaning of an IRD will associate a set of necessary and sufficient conditions that something must satisfy to be designated by the IRD in this or in any possible world:
IRD1: If a speaker knows the meaning of ‘a’ where ‘a’ is an IRD that designates a, there is a condition C that is necessary and sufficient for being a in any possible world that the speaker associates with being a.
We can introduce another notion of an IRD, one that’s a bit more demanding:
IRD2: If a speaker knows the meaning of ‘a’ where ‘a’ is an IRD that designates a, for any condition C, a knows whether C is necessary or sufficient for being a in any possible world.
To see that these notions of an IRD are distinct, suppose there are two conditions, C1 and C2, that a meets. Suppose that satisfying C1 is necessary and sufficient for being a in every possible world. Suppose that satisfying C2 is also necessary and sufficient for being a in every possible world. A speaker might satisfy the conditions set out by IRD1 for knowing the meaning of ‘a’ by associating C1 with ‘a’ without associating C2 with ‘a’. (Similarly, the speaker might associate C2 with ‘a’ without associating C1 with ‘a’ and still know the meaning of ‘a’.) While it would be apriori that a satisfies C1, it might not be apriori that a satisfies C2. According to IRD1, the speaker would know the meaning of ‘a’. According to IRD2, the speaker would not.
It’s quite possible that the notion of knowledge at meaning is itself one that’s subject to various ambiguities. I would like to avoid tricky disagreements as to whether IRD1 or IRD2 captures the true meaning of ‘knowledge of meaning’. There might be a weak sense in which knowing the meaning of ‘a’ requires satisfying the conditions set out in IRD1. There might be a strong sense in which knowing the meaning requires satisfying the more stringent conditions set out in IRD2. To fix meanings, let’s refer to these two kinds of knowledge as knowing the meaning in the weak and the strong sense respectively.
A concrete example might help to illustrate the distinction and help to explain why there’s a potential worry here with Swinburne’s argument. On Swinburne’s view of persons, each person has a thisness that ‘makes’ a person the person he or she is (2013: 151). Swinburne holds that we know the meaning of various IRDs that we can use to designate ourselves:
Now what sort of designator is ‘I,’ or ‘Richard Swinburne,’ as used by me? These seem to be informative designators. If I know how to use these words, I cannot be mistaken about whether or not they apply to a certain person--given that I am favorably positioned (e.g., his body is my body) with faculties in working order, and not subject to illusion. And when I am considering applying these words to a person in virtue of his having some conscious event, these conditions will be maximally satisfied and no mistake is possible. I am, in Shoemaker’s … phrase, ‘immune to error through misidentification’ (2012: 119).
Suppose that that is so. This is consistent with the further idea, defended by Kripke (1980), that certain facts about our origins are necessary for us. If Kripke’s arguments are to be believed (and their conclusions are surely consistent with everything Swinburne has argued for in arguing for dualism), we could not have had our origins in any combination of egg and sperm other than the combination actually was involved in our generation. We can exploit this to introduce further IRDs that designate us that identify conditions we do not associate with ourselves in using ‘I’ to refer to ourselves. Indeed, if successful use of ‘I’ turned on knowing our origins, we would lose this immunity to error through misidentification that Swinburne associates with our use of ‘I’. Thus, there is a perfectly good sense in which George Bush would have grasped the meaning of ‘George Bush’ even if he was in no position to say whether George Bush could have been born into the Kennedy family. As the example hopefully illustrates, knowing the meaning in this weak sense is both consistent with knowledge of meaning in a stronger sense but is not for that knowledge of meaning in a totally uninteresting sense.
Do we know the meaning of, say, ‘pain’ and ‘firing of C-fibers’? Swinburne is surely right that there is a perfectly good sense in which we know the meaning of ‘pain’ if we have had painful experiences and can use this term to describe them in the normal way. We’ve also all read enough philosophy of mind to know something about the firing of C-fibers. The crucial question is what we know in knowing the meaning. Do we know the meaning of ‘pain’ in the weak sense or the strong sense? Suppose that we know the meaning of ‘pain’ and ‘firing of C-fibers’ only in the weak sense. If so, it is consistent with what we know that the criteria of application of ‘pain’ and ‘firing of C-fibers’ will coincide in this and in every possible world. Thus, knowing that ‘pain’ properly applies to something will not put us in any position to know that ‘firing of C-fibers’ does not also apply. Thus, while it might not be apriori that anything that is a pain is a firing of C-fibers, it could nevertheless be necessarily true that it is.
The success of Swinburne’s argument, then, depends upon something quite strong. For any of us to know apriori that a pain is not just the firing of C-fibers, we would have to know the meaning of ‘pain’ and ‘firing of C-fibers’ in the strong sense, not merely the weak sense. I doubt that any of us have this knowledge. I certainly doubt that having this knowledge is what we have when we know what pain is by learning the criteria for its correct application (i.e., how certain things feel). In knowing that I feel a certain way, I can know that it is appropriate to say that I’m in pain but I’m not thereby well positioned to assert the stronger claim that what I’m feeling does not require the firing of C-fibers. What a physicalist should say is that we do not know the meaning of ‘pain’ or ‘firing of C-fibers’ in the strong sense. Once we have distinguished between different senses of knowledge of meaning, there is no reason to be ashamed to say that we don’t have this knowledge now and may never have this knowledge.
The introduction of the distinction between two senses of IRD and two kinds of knowledge of meaning can be independently motivated. Interestingly, it seems to save Swinburne from trouble. Consider the debates between the Cartesian interactionists and the occasionalists. Both parties to this debate presumably knew what ‘pain’ meant in what I’ve called the weak sense. They certainly grasped the criteria for the correct application of the term. What they disagreed about was whether pain was the sort of thing that could be caused or cause a physical thing without divine intervention. The Cartesians would impress nobody with this argument:
Our debate is about ‘pain’. The criteria for the correct application of this term has to do with how the subject feels. Knowing the meaning of ‘pain’ involves grasping facts about how things feel to the subject. We could introduce an IRD, ‘o-pain’, that designates a state that must meet two conditions: having the feel that is characteristic of ‘pain’ and being such that it cannot causally interact with anything physical without divine assistance. Since it is not apriori that pain is o-pain and both ‘pain’ and ‘o-pain’ are IRDs, it is not true that pain is o-pain. Thus, your occassionalist view of pain is mistaken.
The occassionalists could run a parallel argument for ‘c-pain’, an IRD that designates a state that has the felt quality of pain and is such that it can causally interact with something physical without divine assistance. Neither the Cartesian nor the occassionalist would be impressed by the claim that their opponent knew what ‘pain’ meant in the weak and the strong sense. What both parties should say that what they know about the meaning of ‘pain’ is sufficient for them to apply it correctly and concede that their knowledge of the meaning of ‘pain’ leaves unsettled questions about whether pain is c-pain or o-pain.
Suppose Swinburne were to reject my suggestion that there are two notions of IRD at play and two notions of knowing the meaning of an IRD. Suppose he insisted that in knowing the criteria that would enable one to correctly apply an IRD, one is thereby in a position to know apriori the conditions it meets. If he insisted on this, the debate between the Cartesians and occasionalists should worry him.
It does seem that it is apriori that pain is either c-pain or o-pain, but not apriori that it is one or the other. Notice that if all necessary truths are apriori and I’m right about the lack of apriori entailments between ‘pain’, ‘o-pain’, and ‘c-pain’, we can generate a contradiction from Swinburne’s system. These three claims, after all, would constitute an inconsistent triad if all necessary truths are apriori:
(i) Necessarily, pain is either c-pain or o-pain.
(ii) Although I grasp the meaning of ‘pain’ and ‘c-pain’, it is not apriori that pain is c-pain.
(iii) Although I grasp the meaning of ‘pain’ and ‘o-pain’, it is not apriori that pain is o-pain.
To see that these three constitute an inconsistent triad in Swinburne’s system, suppose (ii). Since both ‘pain’ and ‘c-pain’ are IRDs, this entails that pain is not c-pain. This entails by (i) that it is o-pain. This, however, is incompatible with (iii) because (iii) entails that pain is distinct from o-pain.
Such contradictions are easily avoidable if tinker with Swinburne’s system. We can say that there are necessary truths about the relationships between things designated by IRDs that are not apriori. If we said this, we could say that (i)-(iii) are true, but then the fact that it is not apriori true that pain is C-fibers firing would be consistent with the fact that pain just is the firing of C-fibers. Alternatively, we could hold onto the idea that the all necessary truths are apriori and assert that (ii) or (iii) must be mistaken if we concede that what we know about the meaning of ‘pain’, ‘o-pain’, and ‘c-pain’ is sufficient to understand what these terms mean without our understanding putting us in a position to determine which of these claims is true. If we say this, we shouldn’t be moved by Swinburne’s anti-physicalist argument because we’d have to concede that we know what ‘pain’ is only in the weak sense that doesn’t put us in a position to know apriori whether or not it is the firing of C-fibers. There are lots of ways of rearranging the deck chairs so as to avoid an apparent contradiction, but on none of these ways of doing so should we think that we’re in any good position to say what pain isn’t simply by virtue of having a painfully good grasp of what it is.
Everyone knows that there are potential problems with a certain style of apriori argument against physicalism. The apparent cases of aposteriori necessities should worry us that the apparent power to conceive of a real distinction between two things is really just due to our ignorance of the complex ways that these things are. The introduction of the distinction between rigid designators and informative rigid designators was supposed to help us overcome this apparent difficulty, but it hasn’t done so at all. IRDs understood as IRD1s will not underwrite the sort of anti-physicalist argument that Swinburne is after because it is possible to know the meaning of ‘pain’ in the relevant sense without knowing that nothing can be a pain unless it is a firing of C-fibers. IRDs understood as IRD2s will not underwrite the anti-physicalist argument that Swinburne is after because it is not at all clear that we know the meaning of ‘pain’ or ‘firing of C-fibers’ in the strong sense. Our ability to correctly and knowingly apply predicates like ‘pain’, ‘belief’, or ‘desire’ does turn on having criteria for correct application (and so knowledge of their meanings in a weak sense), but not on having the kind of knowledge that’s required for knowledge of meaning in the strong sense. I submit that the introduction of the notion of an IRD has not helped to advance the case against physicalism at all.
In terms of Swinburne’s overall case against physicalism, the failure of his argument for property dualism is significant. Physicalists have long held that it is possible to maintain a perfectly respectable sort of physicalism without any commitment to type-identity theory (i.e., the theory that all mental properties are identical to some physical properties). The physicalists thought that even if type-identity theory might be false, it still might be true that all substances and events were physical substances and physical events. As Swinburne conceives of the terrain, however, the failure of type-physicalism would seem to immediately lead to the failure of physicalism. Events are, on his view, nothing more than property instantiations or changes (2013: 1). If events are conceived of in this way, all mental events must be distinct from physical events once it has been shown that mental and physical properties are distinct. Substances are, on his view, mental if they have any mental properties essentially (2013: 141).
Kripke, S. 1980. Naming and Necessity. Blackwell.
Swinburne, R. 2012. How to Determine which is the True Theory of Personal Identity. In G. Gasser and M. Stefan (ed.), Personal Identity: Simple or Complex. Cambridge University Press.
____. 2013. Mind, Brain, and Free Will. Oxford University Press.