There is no question but that particular goings on in the frog brain play an indispensable role in explaining how frogs catch flies. If there were something in there that had what is for Rosenberg the magical property of being about flies, it would be of explanatory interest only if it played the causal role that the neural state in question plays, i.e., if it typically made its appearance only when a frog is in the vicinity and typically caused frog-catching behavior. Granting that nothing in the frog has the mysterious aboutness Rosenberg rejects, the temptation to point to the neural state that plays this causal role and say this is what aboutness really is is hard to resist. The Rosenbergian claim that it cannot be about anything falls flat absent some account of what it lacks that’s essential to really being about something.
Is there much of anything to the folk-concept of aboutness for science to subvert? In my experience, if someone is asked, “What makes the frog’s idea of the fly an idea, and what makes it an idea of a fly?” the notion that it has to with some sort of resemblance of the mental item to what it represents falls apart quickly, leaving not much of anything that we are entitled to say no mere brain stuff can satisfy.
It’s interesting to ask what could be going on when someone mistakenly believes that something is about something. Someone sees a combination of letters and in error takes it to be a word in a foreign language when in fact it’s just a meaningless combination of letters. Is it conceivable that we are systematically wrong in such judgments, or are errors of this kind parasitic on a background of correct judgments? Or one could encounter a description that fails to refer, e.g., when the student refers to Martin Luther, the German king who was an activist for civil rights for black Protestants in the 1960’s.
The crucial fact lurking here is that nothing in nature fixes reference. There is, perhaps, no objective matter of fact as to what the frog’s brain represents when it catches flies. The frog can be fooled, capturing BB’s as though they were flies, so do the goings on in its brain mean small black thing rather than fly? In some quarters much has been made of the indeterminateness of translation and the inscrutability of reference. This tells us something important about the place of meaning in the natural order, but the conclusion that what it tells us is that there is no place for it, i.e., that nothing is about anything, is hard to believe, or even grasp. I’m no fan of facile objections that charge a view with self-referential incoherence, but it’s hard not to want to ask Rosenberg if the words in his book are about anything, whether reading it doesn’t cause us to think about frogs, and so on. Physics fixes all the facts, and facts about meaning are not facts of physics. But why say this implies there are no facts about meaning? As a scientific naturalist, I want to say that we need to identify neural states as representing things in order to explain the behavior of organisms. (Not to say that there must be a local mapping of the intentional onto the neural, an identification of something in the brain as the representation of something; the brain might be in the state of representing something in virtue of rather global features, on analogy with non-symbolic, parallel computation.) The fact that there is an alternate, lower level, description, couched solely in terms of physics, does not imply that the intentional description is scientifically dispensable.
Sometimes The Atheist’s Guide reminds me of early 20th-century popularizers of science, informing us that there are no solid objects, since what we take to be solid objects are mostly empty space containing atomic nuclei surrounded by mostly empty space. But such a claim strikes us (or at least me) as anachronistic. Of course solid objects exist, and it’s often important to distinguish them from objects that are not so solid, or not objects at all but volumes of liquid or gas. Physics reveals not that there are no solid objects but what solid objects are really like. As Wilfrid Sellars famously said, the task of philosophy is to figure out how the manifest image, i.e., the world as humans experience it fits together with the scientific image. Sometimes this means dismissing something as illusory, a mere artifact of how we represent things, but sometimes it means revising concepts to fit into the world where physics fixes the facts. Recall the issue that led Rosenberg to moral nihilism: our natural concept of a moral fact is of a state of affairs that provides those who detect it with a reason to act. If, as physicalists and naturalists tend to think, there can be no such practical reasons, because all reasons to act are rooted in the agent, not in objective reality, then either moral facts need not have this feature, or there are no moral facts and no moral truth.
Or consider our concept of time. Late in his career Gödel showed that there are physically possible universes in which solutions to the equations of general relativity imply that there are closed, finite time-like loops, which is to say that in those worlds time travel is possible. He saw this result not as implying that time-travel is possible, but that general relativity reveals that what we think of as time is not captured by the fourth, time-like, spatial dimension, and thus that what we think of as time has no objective reality. Talk of time as a fourth spatial dimension is not just a way to interpret general relativity, but the sober truth: there is no such thing as time. Did Gödel draw the right conclusion? Or is the implication that time is real yet quite different than we imagined?
Rosenberg stresses the implausibility of mapping propositional attitudes onto the brain’s physical structure, and the correlative implausibility of its computation being linguiform, or symbolic at all. On the most likely account the brain’s computation is at bottom parallel and non-symbolic, not serial and symbolic. We still need to explain human linguistic competence, the fact, e.g., that anyone who makes sense of, “The dog bit the boy” can makes sense of, “The boy bit the dog,” and it’s at least not obvious how to do so unless some serial computation goes on in one’s head. (In principle a virtual serial machine can run on a parallel machine and a virtual parallel machine can run on a serial machine.) We may have good reasons to reject the idea that in general the computation that makes a brain a mind involves propositional representations of the world, and to reject the idea that mental representations can be identified, even token-wise, with discrete brain events. But there is no reason to think the scientific explanation of human beings can get by without identifying some state of the brain as a representation, as being about goings on in the world outside the brain, even if that information bearing state consists of an activation pattern realized in some ensemble consisting of some very large number of neurons. (The Churchlands make this sort of thing sound very plausible.)
A general question that arises here is how what looks a lot like some version of eliminativism coheres with Rosenberg’s scientism. It’s hard to see how these claims cohere:
(i) Physics fixes all the facts
(ii) Physics fixes all the facts about human beings
(iii) Insofar as human beings as such are subject to scientific explanation it is by means of subsuming them under biological concepts
(iv) Biological concepts cannot be reduced to those pf physics
(v) What cannot be reduced to physics is not real; it’s at best an illusion provided by natural selection
(vi) Science alone provides the sober truth about human beings.
The only way I can make out a coherent view is by rejecting (iv) and claiming that there is an intertheoretic reduction of biology to physics. One the one hand, it might be that natural selection can be understood as a law of physics, though it seems to me that this is arbitrary, in contrast to regarding it not as a law of nature but as an abstract principle true of anything, irrespective of its physical constitution, of which a few things are true, e.g., it makes imperfect copies of itself, properties of the copies have a bearing on the odds of their making more copies, etc. But even if we can include natural selection as part of physics, biological explanation relies on many other concepts and some of these, e.g., gene, seem obviously irreducible to physics in virtue of being functionally defined. Further, if the scientific understanding of minds proceeds largely in computational terms, then while the facts about the mind are fixed by physics, their explanation depends on concepts that cannot be reduced to those of physics. The God Rosenberg finds obviously non-existent could make sense of the world using only the concepts of physics, but probably no finite mind, and certainly no human mind, could do so. We need the special sciences, and probably quite a few other things, even some chastened folk-psychology and history.