Chapter 7: Naturalism and Libertarian Agency
by Stuart Goetz
Goetz's primary argument against naturalism is that libertarian free will falsifies naturalism. If free will exists, then naturalism is false. Formally, we can put the argument like this:
(1) If libertarian free will exists, then naturalism is falseI will clarify a few terms then discuss the argument.
(2) Libertarian free will exists
Therefore (3) Naturalism is false
Libertarian Free Will
Libertarian free will is the idea that choices are not predetermined or fully coerced by law-like forces. Libertarian free will (or libertarianism for short) entails that those who have free will are agents--they are self-directing entities who make choices for reasons. In Goetz's words, "According to libertarianism, a choice is an undetermined mental action which is explained teleologically in terms of a purpose or goal of its agent" (157).
Goetz references the philosopher David Papineau for one definition of naturalism: "Papineau believes that naturalism is a commitment to the completeness of physics, where physics is complete in the sense that a purely physical specification of the world, plus physical laws, will always suffice to explain what happens" (156). Goetz also cites David Armstrong for another defintion: According to [Armstrong], naturalism is 'the doctrine that reality consists of nothing but a single all-embracing spatio-temporal system'" (157). A third way of stating naturalism is that it is the rejection of all things "supernatural." These definitions of naturalism are unified in their rejection of immaterial minds or souls--there is no room in the naturalist picture for some non-physical entity to do any explanatory work in the universe of physical cause and effect. Thus, naturalism is incompatible with substance dualism (dualism being the view that minds and bodies are distinct entities that somehow interact).
The first premise in Goetz's argument--(1) if libertarian free will exists, then naturalism is false--seems to have a lot of intuitive appeal. Given naturalism's exclusive commitment to physical explanations (i.e. the completeness of physics), the concept of an agent who can "interfere" with the natural order is quite outwardly incompatible with the naturalistic picture. Goetz quotes John Searle to substantiate premise (1):
"In order for us to have radical [libertarian] freedom, it looks as if we would have to postulate that inside each of us [our physical bodies] was a self that was capable of interfering with the causal order of nature. That is, it looks as if we would have to contain some entity that was capable of making molecules swerve from their paths. I don't know if such a view is even intelligible, but it's certainly not consistent with what we know about how the world works from physics" (p.170, Goetz's emphases and brackets).Searle and Goetz get the issue right, in my estimation. Since all naturalism permits into the physical world are physical objects, and since naturalism permits physical objects to only move around by way of determinate physical forces, there could not exist a physical object (not even a molecule) that moved so much as a nanometer off its predetermined course because some agent "decided," independently of the dictates of physical law, that it should move off course. If such an agent were permitted into the cause-effect structure of the physical world, the nature of this agent would have to be fundamentally unlike physical objects and physical laws. Insofar as this agent would be moving physical things around for goals or purposes, the agent would be substantially different from anything physical, since nothing in physics is ever supposed to operate according to purposes. Since libertarian free will proposes that agents can manipulate physical objects for purposes, libertarian free will is outwardly incompatible with naturalism.
Goetz suggests that naturalism is incompatible with free will for two related reasons: free will violates causal determinism, and free will implies dualism:
"The bottom-to-top layered picture of the world where the mental is a higher-level feature excludes future-to-present explanation of a choice in terms of a goal or purpose. Thus, while supervenience naturalism is incompatible with libertarianism because of the determinism present in the supervenience relation, at a more basic level it is incompatible with libertarianism because like all forms of naturalism it denies any explanatory role for teleology" (p.171).Goetz's reference to "supervenience naturalism" here refers to the view that the mental is a "higher-level" property of the physical, but it is not independent of the physical. There is a dependency relationship between the mental state and the subvenient physical state such that the mental state only changes insofar as the physical state changes. The mental state, in other words, has no independent causal effect whatsoever on the physical state. Searle is an example of a supervenience naturalist and he has described the supervenience relation of brain to mind as similar to that of water to liquidity: Liquidity supervenes on the H2O molecules that make up the water such that the properties of the molecules instantiate or make it possible that the water has the higher-level property of liquidity; but, the liquidity property itself has no effect on the water molecules. Thus, supervenience is a kind of "bottom-to-top" relationship. Goetz makes it clear in his essay that this kind of relationship of physical-to-mental rules out anything happening for goals or purposes. The mental, on this view, does not enter into the causal picture in a fundamental way and so none of the mental's goals or purposes can explain what happens in the physical world. Goetz goes on to discuss Searle:
"Searle believes (as do most, if not all, supervenience naturalists) that in order for a mental event such as a choice to occur and be explained teleologically, it would have to be an independent deep occurrence of the world, and this would imply that a self exists which is an independent deep entity that makes the choice for a purpose" (p.171-2, Goetz's emphasis).Thus, Goetz draws the conclusion that libertarianism entails the truth of dualism. If it's possible for mental states to affect the physical world for the sake of purposes and goals, then there must be an agent who is generating such purposes and causing physical objects to align with those purposes. If this is correct, then libertarianism is incompatible with naturalism, and premiss (1) is justified.
Now, the second premiss--(2) Libertarian free will exists--is at least supported by common sense experience. The letters and words in a book, for example, appear to be put there by agents who make choices for purposes. Nearly everything we ordinarily take humans to do every day could be accounted for by references to reasons, purposes, or goals of conscious agents. However, as those of us schooled in the philosophy mind well know, this common sense view is challenged by naturalists, usually because they fear it leads to dualism. Dualism is the view that supposes that minds or souls exist independently of brains or bodies. Dualism was made famous by Rene Descartes and it is sometimes called "Cartesianism" or the "Cartesian intuition."
The standard objection to dualism offered by naturalists is that dualism is incomprehensible or incoherent. The objection claims that there is no conceivable way that two radically distinct substances could interact with each other. How could it be, for example, that a mass-less, charge-less, space-less, or generally physics-less entity could affect entities fully comprised of mass and charge, occupying space, and ruled by the principles of physics? This "interaction problem" has been taken to be a decisive refutation of dualism in modern philosophy. Goetz's response to this objection is a good one. He points out that the interaction problem is not unique to dualism, but in fact plagues naturalist explanations of mind as well, including supervenience naturalism. Goetz discusses Jaegwon Kim to this effect:
"As I have argued elsewhere, the supervenience naturalist, in spite of all of his bluster about the problem of causal interaction for dualism, is no better off than the dualist when it comes to explaining how it is that the mental relates to the physical. Thus, Kim himself has stated, 'the problem of mental causation [doesn't] go away when Cartesian mental substance [goes] away'" (p.174, Goetz's brackets).The interaction problem between minds and bodies plagues naturalist accounts of mind to the same extent that it does dualist views because naturalists have no explanation of why it is that physical states cause mental states at all, much less why certain physical states cause certain mental states. All of the appeals to neuroscience to explicate the connection between physical and mental are ultimately only correlative. I.e., the more scientists learn about which parts of the brain are associated with which mental events only goes far enough to establish that the mind and the brain are interacting with each other, but this does not explain how or why the interaction takes place. Goetz points out that the best naturalists can do here is just assert both that there is a deterministic relationship proceeding from the physical to the mental, and that this relationship is simply a "brute fact" of reality that defies any further explication.
Well, how is the naturalist "brute fact" position superior to the dualist position? In both cases, there is an interaction conjectured between mental and physical, and the accounts of how and why the interactions take place are left unexplained. If it is absurd to suppose that the mental sometimes causes physical effects because the mental is radically unlike the physical, then the proposition that the physical sometimes causes mental effects should be equally absurd for the same reason. But, if this is the case, then to the extent the interaction problem defeats dualism, it also defeats supervenience naturalism to that same extent. On the other hand, if the supervenience naturalist is permitted to posit the interaction between physical and mental as "brute," then the dualist should equally be permitted to posit the interaction between mental and physical as "brute." If we go this latter route, though, the standard objection to dualism no longer has any teeth.
Now, if Goetz is right that the mind-body interaction problem is equally applied to both dualist and naturalist positions, then dualism should remain a viable option (assuming there aren't other good arguments against it). If we revisit libertarian free will from this vantage point, it seems that we have a theoretical framework that is compatible with our common sense experiences of free will. Our experiences of making choices for reasons and purposes can be taken as reliable indicators of our free will because we do not have an overriding defeater for that common sense observation. In other words, we have strong experiential grounds for believing we have free will, and the fact that this belief pushes us into dualism is not problematic since dualism is, ultimately, as viable as its competitors. Furthermore, dualism has an advantage over naturalist views in that dualism preserves our common sense understanding of our mental lives. Thus, given the experiential support for premiss (2) plus the lack of a good defeater for belief in (2), and given that premiss (1) is justified as discussed above, the conclusion of Goetz's argument appears to be justified: (3) Naturalism is false.