I. A Version of Nonreductive Physicalism
The exclusion argument works because if token physicalism is true and microdeterminism is true, any causal properties possessed by mental events are possessed in virtue of their physical properties, not in virtue of their mental properties. For physicalists such as Jaegwon Kim (see also 1984, 1993a) there are ontological as well as epistemological consequences to the exclusion argument. The ontological consequence is that mental properties have no independent causal powers of their own. The epistemological consequence is that invoking mental properties in explanation is superfluous.
Robert Van Gulick (1993) draws two main conclusions from his discussion of the exclusion argument. First, he provides an argument to the effect that causal relevance is distinct from causal potency (basically, the idea is that the ontological and epistemological consequences of the exclusion argument are distinct). He argues that if the causal relevance of a mental property is determined by having a useful role in causal explanation, then it is not clear that we should count mental properties as causally irrelevant simply on the basis of their lack of independent causal powers (242-5). Discussion of Van Gulick’s view of causation will follow, but suffice here to note that this conclusion regards epistemology, and is distinct from any ontological consequences Van Gulick draws.
Second, he argues that although the events and objects picked out by the special sciences are composites of physical constituents, it is not the case that their causal powers are determined solely by the physical properties of the constituents of those organized processes; rather, the organization of those constituents into patterns also plays a role in the determination of causal powers. Those organizational patterns turn out to be the referents of the predicates of the special sciences (250). It is unclear exactly what these patterns are supposed to be, and in what sense they should be considered “higher order” than physical properties. However that is resolved, Van Gulick appears to be moving from his thesis about the relevance of higher order properties to causal explanations to a thesis about the causal efficacy of those higher order properties; he is drawing substantive ontological conclusions from his epistemological considerations. He argues for the reality and causal potency of the organizational patterns based on the following:
(1) Organizational patterns are recurrent and stable features of the world.
(2) Many patterns are stable despite variation in or exchange of constituents.
(3) Many patterns are self-sustaining despite physical forces that might disturb them.
(4) Patterns may affect which causal powers of their constituents are likely to be activated. The constituent may have many different causal powers, but only a subset will be active in a given situation.
(5) The selective activation in (4) may contribute to the maintenance of the pattern itself.
On this view, higher order properties act by selective activation of physical powers, not by their alteration (250-2).
Van Gulick argues that even the properties of the lowest levels of the physical organization of things are in fact “stable self-sustaining recurrent states of the quantum flux of an irreducibly probabilistic and statistical reality.” He gives as examples of these recurrent states the property of being a proton or the property of being an electron with ½ positive spin. The fact that the interactions of objects at the lowest level approximate deterministic regularities seduces us into believing that these objects and interactions have a privileged role in determining the organization of the world. Van Gulick sees the exclusion argument as weakened by these considerations in the following ways, then. The complete physical description of the world will have to include specifications of boundary conditions, since the higher order properties and organizations play a role in which causal properties of the constituents of higher order properties are active. But looking exclusively at the lower level constituents and their properties will not reveal the higher level organization. There are no complete translation functions from one level to the other. In addition, special sciences are able to refer to these higher order property instantiations and elucidate the way in which the temporal sequence of events is determined by the interaction of higher level properties (254-5). For Van Gulick this inability of lower level explanations to account for higher level phenomena does not appear to be merely an epistemic limitation; it is blocked in principle by the real causal powers of higher level phenomena.
II. The Problem with Van Gulick’s Response to the Problem
Part of Van Gulick’s objection is that the properties picked out by physics as the basic entities are every bit as abstracted as the higher order patterns and properties picked out by the special sciences. At bottom, how is the property of ‘being a proton’ categorically different than the property of ‘being a belief’? Both are abstractions, so ultimately they have the same ontological status on Van Gulick’s analysis. I am inclined to agree with him. But I think that where Van Gulick goes wrong is in his assertion that properties like ‘being a proton’ constitute actually constitute the lowest level of reality. This I think is incorrect. It is not the properties of protons, electrons, and whatever other entities make up the domain of quantum physics that comprise the basic level of reality (and therefore analysis) on the assumptions of the exclusion argument, but rather the protons, electrons, and other basic elements themselves that do. It is useful to talk about the properties of quantum entities in descriptions of their interactions, but those properties are abstractions, as Van Gulick points out. But the ultimate constituents of higher level properties are not themselves abstractions, but rather entities. If there is a distinction between the entities that occupy the lowest level and the properties that are abstracted over them, then Van Gulick cannot slide so easily from epistemology to ontology.
Without a parallel between physics and the special sciences, Van Gulick loses the analogy that provides his model for how higher order properties can have causal powers independent of their constituents. His argument hinged on being able to move from the epistemic viability of higher order properties to their viability as independent causal agents. If the objects of the special sciences are not in fact at the same level of abstraction as the objects of physics, then Van Gulick’s claim that the organized patterns of high level properties are independent of their constituents cannot gain purchase from physics being in the same boat.
It might be useful to look at an example of the sort of higher level process that is supposed to be causally independent and capable of downward causation. Van Gulick’s article is light on examples, but I think the sort of thing he has in mind is something like the developmental processes studied in biology. Developmental systems theorists often point to the interaction and complexity of developmental systems as an indication that genetic reductionism is a flawed perspective from which to analyze what’s going on in the production of phenotypes or other biological processes. Developmental systems are composed of a multiplicity of entities and processes and their interactions, including codons, noncoding DNA sequences, epigenetic and regulatory machinery, etc., each of which plays a role in the production of phenotypic effects. Some biologists argue that it is not practically possible to functionally decompose the developmental system into discrete parts and predict the behavior of the system on the basis of the properties of the individual constituents. Developmental systems theorists might also talk about the role developmental systems play in higher level processes; many evolutionary biologists consider the changes that take place in lineages of developmental systems to be a key (or even “the” key) unit in phylogenetic change over evolutionary time (Sterelny and Griffiths 1999: 94-100).
These then would seem to be prime candidates to serve as examples for Van Gulick. However, none of this implies that there are higher level system properties that exercise downward causal force to determine what is going on in the biochemical reactions that comprise the system. For each element of the system there is a mechanism that is, at least in principle, specifiable in terms of the basic constituents of the system and their interactions; there is no top-down pressure required to explain what is going within the system. There is broad agreement within biology about metaphysical reduction and the idea that higher level systematic properties and processes are determined by lower level, physical ones. Debate in biology about reduction is about the epistemological aspects of theory reduction and explanation (Rosenberg 2007: 120-121). Ultimately, it may not be possible to have a useful developmental theory that refers only to atoms and molecules, but that does not indicate that the pragmatics of explanation dictate the positing of higher level phenomena with independent causal powers. The pragmatic requirements of explanation do not dictate the ontological commitments of biology.
In the same way, nothing Van Gulick has given us should prompt us to abandon the metaphysical consequences of the exclusion argument. His failure to recognize a distinction between the constituents of higher level properties and the abstracted properties of those constituents has forced him to blur the boundaries between metaphysics and epistemology, and he has taken his epistemological conclusions to have substantive consequences for ontology. I suspect that despite explicitly recognizing that pragmatics should drive our explanatory frameworks, he fails to notice that the coarseness of the grain of our explanations does not have ontological consequences. What Van Gulick is seeing is the variety and complexity in the lower level systems which produce higher level properties that can be productively grouped into multiply realizeable kinds for the purpose of analysis and that the details of the physical systems that exhibit that complexity do not directly contribute to special science explanations and takes from that a real gap in the actual causal properties of the higher and lower levels. The differences he notices that seem to indicate an incongruity between the causal properties of the low level processes and entities that constitute higher level properties and those of the macrolevel patterns that are analyzed by the special sciences are in reality epistemological distinctions that need not indicate a real metaphysical divide. What Van Gulick has done is mistake a mismatch in grain of different types of explanations of one event or process for a true ontological divide that requires the positing of downward causation to make the world intelligible.
Kim, J. 1984. “Epiphenomenal and Supervenient Causation.” In Kim 1993, pp. 92-108.
Kim, J. 1993. Supervenience and Mind: Selected Philosophical Essays. Cambridge: Cambridge Press.
Kim, J. 1993a. “The nonreductivist’s troubles with mental causation.” In Kim 1993, pp. 336-57.
Rosenberg, A. 2007. “Reductionism (and Antireductionism) in Biology.” In D. Hull and M. Ruse (eds.) The Cambridge Companion to the Philosophy of Biology. Cambridge: Cambridge University Press
Sterelny K. and P. Griffiths. 1999. Sex and Death: An Introduction to the Philosophy of Biology. Chicago: University of Chicago Press.Van Gulick, R. 1993. “Who’s in Charge Here? And Who’s Doing All the Work?” in J. Heil and A. Mele (eds.) Mental Causation. Oxford: Clarendon Press, pp. 233-56.