Abstract
The Doctrine of Microphysical Supervenience states that microphysical duplicates cannot differ in their intrinsic properties. According to Merricks (Mind 107(425):59–71, 1998a, Objects and persons, Oxford University Press, 2001), however, this thesis is false, since microphysical duplicates can differ with respect to the intrinsic property of consciousness. In my view, Merricks’ argument is plausible, and extant attempts to reject it are problematic. However, the argument also threatens to make consciousness appear mysterious, by implying that consciousness facts fail to be microphysically determined and that there can be brute and inexplicable differences in consciousness between material things. The paper therefore develops an account that can respect the soundness of Merricks’ argument while avoiding these problematic consequences. At the heart of the proposal is the idea that consciousness can be microphysically grounded despite failing to microphysical supervene. The proposed view also has the interesting consequence that consciousness is an intrinsic property despite depending on extrinsic factors for its instantiation.
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Notes
Note that we must restrict the intrinsic properties and atom-to-atom relations that we take into consideration if we are to avoid irrelevant and distracting counter-examples (cf. Merricks, 1998a: 69–60; Sider, 2003: 140–141). Following Merricks (1998a), one option is to restrict our attention to just those intrinsic properties and interrelations that are pure and qualitative, and to all and only those atom-to-atom relations that are spatio-temporal and causal. One might also appeal to Lewisian perfectly natural properties and relations as in Gilmore (2010: 185).
Note that no particular conception of consciousness is required for the argument to work.
Microphysical duplicates in this sense will share all and only those of their microphysical properties that are intrinsic, i.e. those that are a function of what their constituent atom are intrinsically like. Later on, however, we will have cause to distinguish between objects that are microphysical duplicates in this restricted sense, and objects that are microphysical duplicates simpliciter, i.e. that share all of their microphysical properties both intrinsic and extrinsic (cf. Sect. 4 below).
I assume, with Merricks, that human persons are composite material objects of some sort. Throughout, I will write as if we human persons are whole-bodied human beings. However, nothing really turs on that being so. It is enough for us to be complex material things of one sort or another. For example, as a referee points out, we might even be brains of human beings or other such parts. (Any view that Zimmerman calls ‘sensible materialism would do. As long as humans are complex wholes and natural kinds with plausible maximality constraints on their instantiation, both Merricks’ argument as well as my own reply is going to go through. Not having to commit myself to the idea that human persons are any one type of complex whole is thus in fact all to the good.)
It is irrelevant to argue that this kind of case is nomologically impossible. The case need only be metaphysically possible, and this seems hard to deny (cf. Merricks, 1998a: 64–65).
One could deny that persons are material objects without embracing dualism, e.g. by claiming that persons are events constituted by material goings-on. Robinson (2006) argues that such a move could help undermine Merricks’ argument; however, see Kovacs (2010) for important criticism of this idea. As for the view that each of us contains manifold conscious proper parts, I grant that some philosophers might not be unhappy with such a view. In my view, however, this position is very hard to take seriously (for persuasive argument against this kind of view see Olson, 1995). It also generates various important ethical puzzles and paradoxes (cf. Johnston, 2016; Unger, 2004, 2006).
What about extrinsic mental properties (involving, for example, “wide” intentional content)? My own view is that if there are such properties, then this shows that consciousness is a “hybrid” property that can be had both intrinsically and extrinsically (cf. Bader, 2013 for discussion of such “hybrid” properties). So long as consciousness can be had intrinsically, however, the central arguments of this paper will remain substantially the same (though we would need to make appropriate changes to (MS) and to the thesis I will later refer to as (MG), so that the focus is on properties that are had intrinsically rather than properties that are intrinsic). For ease of presentation, I will continue to focus on the idea that consciousness is intrinsic. But those who think there are extrinsic mental properties should keep in mind that we could easily retreat to the very plausible, though somewhat weaker, idea that that consciousness can be had intrinsically (which would follow from there being at least some mental properties that are intrinsic). Cf. Merricks (1998a: 61, fn. 6).
But there are two further points to make. (1) Some mental properties may be ‘wide’ without thereby being extrinsic. And perhaps these are the only such properties we should grant. And (2) even if some properties are wide and thus extrinsic, they may not be conscious in the sense needed to generate the kind of worries about overpopulation of phenomenally conscious beings that Merricks is concerned with. Both points are plausible, and would of course grist to my mill.
For further helpful discussion of the options for responding to Merricks’ argument see Kovacs (2010).
One might think that a more precise analogue principle would involve an “inter-object” rather than an “intra-object” grounding claim, i.e. something along the following lines:
(MG*) If an object, O, is composed of some atoms, the XXS, and if O has some intrinsic property, F, then O has F in virtue of the fact that the XXS are G*, where for the XXs to be G* is for them to instantiate certain intrinsic properties and/or stand in certain interrelations.
Interesting questions arise about the precise relationship between (MG) and (MG*), though here is not the place to pursue them. I choose to focus on (MG) in the present paper primarily for ease of presentation, and I doubt that much of great importance turns upon this choice. For discussion of a principle very much like (MG*) and of a puzzle it gives rise to, see Moran (manuscript).
For an introduction to the relevant notion of metaphysical grounding see Audi (2012); Fine (2012); Rosen (2010); and Schaffer (2009), among many others. There are many controversies about the precise nature of metaphysical grounding, but we do not need to engage with these here. What I have in mind is a relation of metaphysical determination that is hyperintensional in character and that has certain distinctive formal characteristics, namely it is asymmetric, irreflexive and transitive. I assume that grounding claims in general be expressed by the ‘in virtue of’ locution.
This flows from the fact that grounding and supervenience are distinct relations with different characters. Cf. Schaffer (2017: 10): ‘With supervenience, one simply has two families of properties, and one can only ask whether or not they modally co-vary. With grounding, one has a relation of directed dependency, with a more articulated structure’. Cf. Horgan (1993) and Kim (1993: 167).
Note that the truth of Generality would also help to explain why a related principle is true, which, following deRossett (2010), we can refer to as the Determination Constraint. This tells us that if something is F in virtue of being G, then, necessarily, anything that’s F is G. As Wilsch (2015) explains, this principle is very plausible, but also needs explaining. The thing to note is that if Generality is true, this would explain the principle in a straightforward way. For, given that ground is factive, Generality straightforwardly implies the Determination Constraint.
Notice that to generate the worry here, standard grounding necessitation principles will not do. Standard such principles say that if a is F in virtue of being G then necessarily if a is G then a is F. (They concern, therefore, only one object: if it is F in virtue of being G, then necessarily, when it is G, it is F.) But [5] and [6] only seem inconsistent if we have a principle concerning not just what happens when both (i) a is F in virtue of being G in the actual world and (ii) a is G in other worlds (namely whether x is also G in that world), but rather than (i) a is F in virtue of being G in the actual world and (ii) for any whatsoever if that x is F in any other world (namely whether x is also G in that world). This is why we must appeal to Generality to generate the argument and not to a more standard necessitation principle, even though contingent grounding (which I bring in later) is indeed standardly and in the first instance seen as challenging grounding as a necessitating relation.
Granted, to reject the idea that just because Mary is conscious in virtue of having M, then necessarily if Mary has M, then she is conscious for that reason, we do not need to reject Generality, but rather only a more standard ground-theoretic necessitation principle e.g. such that if a is F in virtue of being G then necessarily if a is G then a is F (in virtue of being F). However, if what we want to reject is not just the idea that because Mary is conscious in virtue of having M, then necessarily, whenever Mary herself has M, she is conscious for that reason, but rather that whenever Mary is conscious in virtue of having M, then necessarily if any object whatsoever has M, then that thing is conscious for that reason, (and note that is the thought we want to deny in allowing that [5] and [6] might be true at once), what needs denying is Generality and the association Determination Constraint (and note again that the former entails the latter given the factivity of ground. Cf. fn. 13 above.).
This is especially plausible on the kind of neo-Aristotelian metaphysical picture that draws a sharp distinction between what an object is on the one hand, and merely how it is on the other. On this view, to say what an object is, one has to specify the kind of thing it is. Whereas to specify how it is, one has to list its properties/relations. A crucial part of the picture is that in a certain sense, the kind of thing an object is classifies as prior to what properties it has: being the kind of thing it is determines the range of features it can have, and so in this sense, what the object is determines how it can be. For a recent defence of this kind of picture see Wiggins (2001); cf. also Moran (2018).
Note, then, that the distinction between grounds and conditions is meant to be metaphysically robust. In the causation literature, it is common to deflate the analogous causes/conditions distinction, arguing that what counts as a cause and what as a background conditions can depend on contextual matters. The view I have in mind here, however, which distinguishes grounds and conditions, implies a robust distinction between the things that are grounds and the things that are enabling conditions which is not context-sensitive in this way. (For a defence of the idea that we can draw a metaphysically robust distinction between grounds/conditions see Bader 2015.)
For example, Fine (2015, 2016) argues that we need to make use of conditional grounding in order to properly model the role that the existence of facts play with respect to the holding of diachronic identities. Meanwhile, Ralf Bader (manuscript‐b) and Ted Sider (2020) argue (independently) that we should appeal to conditional grounding (which Sider refers to as ‘grounding‐qua’) in order to handle the problem of truth‐grounding universal generalisations. Moran (2018) has put the view to work in the context of dealing with the problem of coinciding objects. And Bader (2015) has argued that we need the notion of conditional grounding in order to properly model the way in which reasons can vary across contexts (cf. Dancy, 2004; Ch. 3). The notion of conditional grounding is also somewhat similar to the notion of an ‘anchor’ in Epstein (2015), due to the fact that anchors are not grounds but rather that which enables other things to do their grounding work.
Shoemaker (2008) develops this view by claiming that persons persist by psychological continuity, and that persisting in this way is necessary for being conscious.
Importantly, for the view that personhood is a condition on consciousness to be at all plausible, we need a weightier conception of personhood than the standard neo-Lockean conception, on which being a person is just a matter of being a self-conscious entity. Rather, we need to view persons as a distinctive kind of thing, whereby being this kind of thing is a precondition for consciousness. Cf. Bader (manuscript-a: fn. 6).
For this suggestion see Ayers (1969: 98–99): “[I]t is at least a philosophical possibility, and by no means contrary to common sense or to science, that any experience is necessarily the experience of an animal…”.
In this second case, rather than Mary meeting a condition that enables her to be conscious in virtue of having M, Martha-Minus meets a condition that disables her from being conscious for that reason. But the crucial difference between Mary and Martha-Minus is still a difference in kind.
Instead of appealing to a difference in kind, we might instead appeal to other resources. For instance, we might appeal to a difference in essence between persons or person-parts, or to a difference in form. Insofar as it is plausible to view the kind, or essence, or form…etc. of an object as able to determine the range of properties a thing can have, we could appeal to any such a difference in order to offer a structurally similar account to the one that I have sketched in the main text. So even those unsympathetic to the neo-Aristotelian metaphysic sketched above could still endorse a version of the general view I wish to hold, on which we can accept (MG) while rejecting (MS).
We might also simply impose maximality as the condition that the person must meet in order to be conscious. That is, rather than requiring that the person be this or that kind, we just say that to be conscious x must be a maximal whole. My own view, however, which I lack space to develop here, is that kinds, if treated sufficiently robustly (as described in fn. 15) are much better to play the role of the kind of condition on consciousness that I have in mind. Part of the reason here is that I think we can explain plausibly why kinds are maximal (cf. Sect. 4) and then appeal to kinds as plausible conditions on consciousness. To pursue the other strategy, however, one would have to argue that maximality is itself a condition on consciousness, which seems to me harder to do.
There is, in fact, room for a version of my view on which kinds act as partial grounds. However, this version of the view still requires the machinery of conditional grounding if it is to avoid the kind of worry that we focus on in the next section. Cf. fn. 27.
This is certainly so for macroscopic objects, such as human persons are on a materialist view (of the sort I have been presupposing here). Cf. Fine (2008: 105) on statues and pieces of clay.
This is certainly so for macroscopic objects, such as human persons are on a materialist view (of the sort I have been presupposing here). Cf. Fine (2008: 105) on statues and pieces of clay.
I am assuming, here as throughout, that micro-based properties of the form being composed of atoms with such and such intrinsic properties and interrelations are themselves intrinsic. After all, such properties are a function of what the atoms composing an object are intrinsically like. For some interesting complications here, however, see Moran (manuscript).
On the difference between (i) the local ‘intrinsically/extrinsically’, distinction, which distinguishes two ways a property can be had, and (ii) the global ‘intrinsic/extrinsic’ distinction, which distinguishes two second-order properties that properties can have, see Dunn (1990: 183) and Humberstone (1996: 206, 227–228).
There is an alternate way of developing the kind of account I wish to defend here that does not have this consequence, on which we are to view kind-properties as both intrinsic and subject to maximality constraints. Suppose we said that when x is a person, x is a person solely in virtue of instantiating certain more basic intrinsic properties, but only on the condition that x is not a larger proper part of a person. On this view, we could maintain that maximal kind-properties like personhood are intrinsic: when a being instantiates one of these kinds, this will be in virtue of some particular set of intrinsic base properties, but the grounding relation will hold only given that the being in question meets certain maximality conditions. Notably, such a view would also enable us to view kind-facts themselves partial grounds of consciousness—when x is conscious, the grounding relation would hold unconditionally, and the fact that x is the kind of thing she is would be a partial ground of her being conscious; however, the fact that x is the kind of thing she is would be conditionally grounded in certain microphysical properties whereby the condition is that the person meet a certain maximality constraint. Thanks to Nick Jones for discussion of this alternate view.
One worry here is that this view conflicts with the plausible thought that intrinsic properties must be preserved across Lewisian duplicates. After all, so the thought goes, Mary and Martha-Minus are surely such duplicates. So if consciousness is intrinsic, and yet Mary and Martha-Minus differ in consciousness, then the intuitive idea that Lewisian duplicates must share intrinsics will be undermined. (Thanks to Ted Sider for raising this objection.) In reply, I’d want to make two points. First, it isn’t clear just what the cost is, in the present context, of denying that Lewisian duplicates can differ in intrinsics. This is, I think, no more surprising than the claim that microphysical duplicates (in the sense of that term defined in Sect. 2) can differ in consciousness, but this is also a crucial part of the account I wish to advocate. Moreover, the duplication account of intrinsicality is rather problematic (cf. Bader, 2013), and so questions arise about just how costly it is in general to deny that Lewisian duplicates never differ in intrinsics. Second, it isn’t clear that we must grant that Mary and Martha-Minus are Lewisian duplicates in the first place. Indeed, if consciousness itself is a perfectly natural property, as it is not implausible to think, then Mary and Martha-Minus will not be Lewisian duplicates due to the difference in consciousness between them.
For or a similar criticism of semantic maximality see Jones (2010: 38), who notes, quite rightly, that when we have ‘genuinely metaphysical problems…that wouldn’t have arisen had we used words differently and that can’t be resolved by a more nuanced conception of word- world relations—then semantic-maximality cannot help…’. Cf. also Merricks (2001, 2003: 155–156).
Thanks to an anonymous reviewer for getting me to be much clearer on these points.
Note also that by avoiding the mighty host of conscious beings, we manage to avoid one important version of Mark Johnston’s “personite problem”. However, essence-based version of the problem, relying on the premise that all available essences are in fact instantiated (cf. Chihara 19,940, remains, as does the version that arises naturally from a temporal parts framework. Likewise, the similar problems realised in Unger (2004, 2006) remain as well, since these are motivated by the considerations that generate the “problem of the many” and hence demand a separate treatment.
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Acknowledgements
Versions of this paper were presented to the Serious Metaphysics Group at Cambridge University and to the 2016 Metaphysical Mayhem conference at Rutgers University; thanks to all of the participants on those occasions. Thanks especially to Ralf Bader, Dominic Alford-Duguid, Tim Crane, Ross Cameron, Clint Dowland, Nick Jones, Rae Langton, Mark Johnston, Hugh Mellor, Daniel Muñoz, Jonathan Schaffer, Nathaniel Baron-Schmitt, Ted Sider, Aimee Thomasson, Dean Zimmerman, and to two referees at Philosophical Studies. Some of the work for the paper was completed at Cambridge. Whilst in receipt of Aristotelian Bursary from the Aristotelian Society, a Jacobsen Fellowship from the Royal Institute of Philosophy, and a Mind Studentship from the Mind Association. The paper in its current form was written at Oxford as a Leverhulme Early Career Fellow. My thanks to these institutions and funding bodies for their support.
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Moran, A. Living without microphysical supervenience. Philos Stud 179, 405–428 (2022). https://doi.org/10.1007/s11098-021-01664-7
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DOI: https://doi.org/10.1007/s11098-021-01664-7