Research Comment on "Grounding Physicalism and the Explanatory Gap"

Comment on “Grounding Physicalism and the Explanatory Gap”

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This paper this post comments on can be found here.

By Gene Witmer

Zach Blaesi sums up his thesis in the following dilemma:

Dilemma: Either Grounding Physicalism leaves a genuinely explanatory gap, or the Grounding Physicalist must provide a reductive account of consciousness, thereby giving up one of the central motivations for the view. (15)

In my comments I focus on two issues.

The first concerns the claim that a central motivation for Grounding Physicalism is to avoid commitment to a reductive account of consciousness. While avoiding commitments in general might seem salutary, I don’t think the promise of this approach to formulating physicalism depends on avoiding reductive commitments—not, at least, the way Blaesi is thinking of reductive commitments. Even if the Dilemma thesis is true, then, it seems to me that a Grounding Physicalist can take it in stride.

The second issue is the argument on offer for that thesis. Much of the work Blaesi does in this paper is devoted to supporting the thesis that what he calls “grounding phenomena” need to be explained in a certain fashion—namely, by appeal to facts about the essences of the entities involved. Curiously, one can easily take on board everything he says about this need while resisting the Dilemma thesis. There is a way for a Grounding Physicalist to close the relevant explanatory gap without incurring reductive commitments—at least, there is a route in logical space for her to do so. What’s more, Blaesi himself recognizes this route. He offers some inconclusive reasons to think that this strategy won’t be available after all. I close by offering an example that should make it more plausible that such a strategy is available.

1. Grounding Physicalism and reduction

Blaesi tells us that Grounding Physicalism has “significant advantages over the traditional options” and describes those advantages as follows:

The appeal of Grounding Physicalism is that it promises to occupy a middle position between reductive and non-reductive versions of physicalism. On the face of it, Grounding Physicalism is less demanding than reductive versions of physicalism, because it does not require that mental phenomena be identified with (or defined in terms of) physical phenomena. On the other hand, unlike some versions of non-reductive physicalism, it can adequately capture the idea that the mental depends on and is explained by the physical. (2)

The description of Grounding Physicalism as occupying a middle position “between reductive and non-reductive versions of physicalism” is unfortunate: one would have thought that reductive and non-reductive versions exhaust the options. But I presume this is a slip. From the paper, it seems that he has in mind just one sort of position as constituting non-reductive physicalism, namely, supervenience based formulations. So Grounding Physicalism is appropriately stronger than those supervenience versions yet not so strong as to commit the physicalist to a reductive account of conscious states.

What exactly qualifies an account as reductive in the first place? Blaesi offers a disjunction: reductive accounts require that “mental phenomena be identified with (or defined in terms of) physical phenomena.” The latter option is clearly meant to include any identification of mental properties with functional properties—or, at least, functional properties of a certain kind, namely, those such that the relevant functional roles can be spelled out entirely in terms of interactions with physical properties or events. Presumably other means of definition are included as well, such as identifying a mental property with a conjunction of physical properties, and a fully precise story would specify an acceptable class of defining operations. I won’t venture such a story here, but my point is to emphasize that the operative notion of reduction is relatively expansive. Historically, functional accounts were thought of as non-reductive because they did not commit to identities between mental properties and first-order physical properties, but here they are classed as reductive.

In light of this it is especially important to ask about the motivation for avoiding reductive commitments. Evidently it cannot be the desire to accommodate multiple realizability. A clue as to how Blaesi sees the motivation can be found in the following remark he makes about Grounding Physicalism at the end of his discussion of its advantages:

Finally, Grounding Physicalism is immune to the charge (often raised against reductive physicalism) that it leaves out the most important part of consciousness. That is because Grounding Physicalism does not entail that phenomenal properties are reducible to physical properties. It is consistent with Grounding Physicalism, for example, that the essence of pain is exhausted by its “what-it’s-likeness.” (4-5)

The motivation for avoiding reductive commitments here is to enable us to say that the essence of a conscious state is “exhausted” by its “what-it’s-likeness.” But I confess to finding this quite puzzling. After all, a physicalist may agree that the essence of pain, for example, is indeed exhausted by its what-it’s-likeness while holding that its what-it’s-likeness just is identical with such-and-such physical property. In that case, though, a paradigmatically reductive account is consistent with this allegedly anti-reductive motivation.

Of course, one might appeal to the idea that the essence of pain is exhausted by its “what-it’s-likeness” as a way of arguing against the identification of pain with any physical or functional property. But two points need to be recognized. First, no such argument can succeed without significant additional premises. Certainly one can point to the fact that for any given physical property, that property seems not to be identical with the “what-it’s-likeness” of pain, but this appearance is acknowledged on all sides not to be enough on its own to overthrow the identity claim. Additional claims are needed to ensure that this is not a mere appearance. Second, arguments that take on that additional dialectical burden are liable to be arguments against physicalism itself. After all, it also seems that the “what-it’s-likeness” of pain has to be something over and above any and all physical features one can think of; and since physicalism has to say that the mental facts are nothing over and above the physical facts, leaning on this sort of point to motivate a formulation of physicalism that avoids reductive commitments is perverse. One might as well use it to motivate a formulation of physicalism that avoids a commitment to physicalism.

It seems to me, then, that there is no good reason for a Grounding Physicalist to be especially concerned to avoid a reductive account of consciousness. Be that as it may, let’s turn to Blaesi’s argument for the Dilemma thesis.

2. The explanatory gap for Grounding Physicalism

The explanatory gap on Blaesi’s construal of it here focuses on what he calls the grounding phenomena—”the facts about what grounds what and the grounding patterns” (11-12). Let’s use the simple example relying on the familiar fiction about c-fibers.

 (1) The fact that Jones is in pain is grounded in the fact that Jones’ c-fibers are firing.

As Blaesi notes, if we accept (1) we already think that a certain kind of explanation of conscious states is available. If the fact that Jones’ c-fiber firings grounds the fact that Jones is in pain, then the former fact indeed explains the latter fact. The explanatory gap objection is reinstated at a different location, however, since now it is (1) itself that needs explaining. But why suppose there is any difficulty for a Grounding Physicalist who aims to explain (1)?

The main consideration advanced is that she cannot take advantage of a well-known strategy for dealing with explanatory gap objections, a strategy exemplified by David Papineau’s remark that identities need no explaining. If pain is identical with c-fiber firing, then—it seems clear—insisting on an explanation for why pain is just c-fiber firing is confused. It’s not the sort of thing that can be explained.

By contrast, grounding phenomena like (1) are the sort of thing that can be explained and, moreover, should be explained by reference to the nature of the entities involved. So an explanation of (1) will need to appeal to the nature of pain and/or the nature of c-fiber firing. I agree. None of this adds up to a reason to think the explanation is bound to commit the Grounding Physicalist to a reductive account. Suppose that (2) is a fact about the nature of pain:

(2) It lies in the nature of pain that necessarily, if an organism’s c-fibers are firing, that organism is in pain and its being in pain is grounded in the fact that its c-fibers are firing.

Of course, (2) itself hardly looks like a plausible claim. My point is not to defend the truth of (2); my point is just to make plain the legitimacy of using a fact like (2) to explain a fact like (1). The salient feature of this fact is that nothing about it requires that pain be identical with a physical property or any property definable in physical terms, including functional properties. There is, then, undoubtedly room in logical space for a Grounding Physicalist to offer an explanation of grounding phenomena such as (1) in a way that does not commit her to a reductive account of any conscious state.

Interestingly, this is not news to Blaesi. He himself notes that a move of this sort is in principle available. He writes:

The Grounding Physicalist’s only hope of closing the explanatory gap is to say something about the nature of consciousness that accounts for the grounding phenomena involving it. This does not automatically commit the Grounding Physicalist to giving a reductive account of consciousness. There are a number of non-reductive positions that arguably incur essentialist commitments. The nonreductionist about determinable colors might deny that there is a full real definition of red in terms of the determinate shades of red but concede that it is essential to red that for any x, if x is scarlet, then the fact that x is scarlet grounds the fact that x is red. It is open to the Grounding Physicalist to likewise claim that the essence of pain lists out each of its grounds, even though there is no biconditional analysis of pain in terms of those grounds. (14)

Quite right; so why think the Grounding Physicalist faces any problem here at all? At this point, Blaesi points out that “the paradigm cases in which we have reason to posit essentialist truths … without giving a full reductive account of that phenomena” are cases in which we have a priori justification for those essentialist claims (14-15). It is, for example, a priori that being scarlet grounds being red. But this seems to be “not a good model” for the Grounding Physicalist, as any such informative facts about the nature of pain seem bound to be a posteriori.

Let me grant this point. On the face of it, the point seems not very relevant. How could the fact that we need empirical information to know something about the nature of pain imply that what we can in this way know about that nature cannot take a certain form—a form exemplified by (2), one without commitment to a reductive account of pain?

Well, I am likely asking for too much. It may be that Blaesi’s point is only that the strategy available in principle to the Grounding Physicalist for avoiding the Dilemma thesis is one that has no precedent in practice, that we don’t have any other examples of a non-reductive essence claim that is empirically discovered. Well, perhaps. But let me try out an example to the contrary.

Suppose that Amy decides on the spur of the moment to treat Basil, a local man down on his luck, to a meal at a nearby restaurant. The meal causes Basil great happiness. Let us agree that Amy’s action is morally good, or at least to some extent morally good. Plausibly, its being to some extent good is grounded in the fact that it caused an increase in happiness. One hardly need adopt a general utilitarian principle that goodness is only a matter of maximizing happiness to accept that an action that increases happiness is, to that extent, a good one.

Now suppose further that happiness is identical with a kind of brain state; for fun, let us say that happiness is having one’s h-fibers firing, and the more h-fiber firing there is, the happier one is. In this example, then, we have the following grounding fact:

(3) The fact that Amy’s act was to an extent morally good is grounded in the fact that it caused an increase in the firing of h-fibers.

Since the increase in h-fiber firing just is an increase in happiness, (3) seems entirely plausible. Can (3) be explained by reference to the the nature of moral goodness? Certainly; we can appeal to (4):

(4) It lies in the nature of moral goodness that, necessarily, if an act causes an increase in h-fiber firing, it is to some extent morally good, and its being to some extent morally good is grounded in the fact that it caused an increase in h-fiber firing.

So we have closed the explanatory gap that might come along with (3). But did we, in closing that gap, commit ourselves to a reductive account of the nature of moral goodness? Certainly not. A claim like (4) can be endorsed without supposing there is any way to identify moral goodness with a property definable in non-moral terms. As noted, one need not endorse utilitarianism to endorse this claim.

Further, of course, (4) is an a posteriori claim about the nature of moral goodness. So this example shows how someone could use an a posteriori claim about the nature of some phenomenon to explain the relevant grounding facts without being committed to any reductive claim about that phenomenon. Of course, my example doesn’t show how to close the explanatory gap for consciousness in this way, but it provides an example of the sort that Blaesi seems to think cannot be found: a nonreductive essence claim that is both a posteriori and suited for explaining the grounding facts.

To sum up: There is, I have argued, no good reason for a Grounding Physicalist to be determined to avoid reductive accounts of conscious states in the first place. If, though, for some reason she wants to do so, Blaesi has not given us any good reason to think she can’t.


D. Gene Witmer is Associate Professor of Philosophy at the University of Florida. His research has focused on topics in metaphysics and philosophy of mind, including physicalism, the place of consciousness, a priori knowledge, and the nature of intrinsic properties. Recent papers include “Physicality for Physicalists” (Topoi 2016) and “Platonistic Physicalism without Tears” (Journal of Consciousness Studies 2017).


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