The Physicist Sean Carroll on (Scientific) Emergence

Sean Carroll is a physicist, cosmologist and research professor at the Department of Physics at the California Institute of Technology. 

In 2010, Carroll was elected as a fellow of the American Physical Society for "contributions to a wide variety of subjects in cosmology, relativity, and quantum field theory and public science education".

This piece itself is based primarily on Carroll's book The Big Picture: On the Origins of Life, Meaning and the Universe Itself (2016). The chapters entitled 'Reality Emerges' and 'What Exists, and What Is Illusion?' are particularly relevant.

It may be worth noting here that at various points in the following I found it hard to distinguish whether or not Sean Carroll was simply explaining/describing a theory/position or endorsing it. Perhaps that's because his primary purpose (at least in these instances) was educational.

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It's the case that just about all scientists accept some kind of emergence. The kind they accept is usually classed as “weak emergence”. Indeed the philosopher Mark A. Bedau has said that “the notion of weak emergence is metaphysically benign”.

Physics (if we can speak in the singular) itself has its own definitions of emergence. Take this one:

"An emergent behavior of a physical system is a qualitative property that can only occur in the limit that the number of microscopic constituents tends to infinity."

In terms of examples. Biologists tend to see life or biology as an emergent property of chemistry. In chemistry itself it's believed that new properties are formed due to chemical reactions and suchlike. And in physics it's said that the properties of water (or even water itself) are emergent in the sense that they're unpredictable even after gaining knowledge of all the properties of its constituent atoms (of hydrogen and oxygen). In addition, in continuum mechanics we have the emergent properties of elasticity, viscosity, tensile strength, etc. Above and beyond all this are the examples which Sean Carroll himself cites in his book and elsewhere. Basically, there is a huge number of emergent properties in the natural world.

Strong emergence particularly often describes the whole's (or the system's) impact on its parts. That's sometimes categorised as “downward causation”. However, it can be said that there's no necessary link between strong emergence and downward causation, even if it strong emergence does occur.

The physicist Philip Anderson puts the case for strong emergence here:

“At each stage, entirely new laws, concepts and generalisations are necessary... Psychology is not applied biology, nor is biology applied chemistry.”

Murray Gell-Mann seems to strike a middle-way between strong and weak emergence in the following quote. Here's the hint at strong emergence:

“[I]t's essential to study biology at its own level, and likewise psychology, the social sciences, history, and so forth, because at each level you identify appropriate laws that apply at that level.”

And then Gell-Mann also hints at weak emergence:

“Even though in principle those laws can be derived from the level below plus a lot of additional information, the reasonable strategy is to build staircases between levels both from the bottom up (with explanation in terms of mechanisms) and from the top down (with the discovery of important empirical laws). All of these ideas belong to what I call the doctrine of 'emergence'.”

The philosopher Mark A. Bedau, on the other hand, puts the argument for suspicion of strong emergence when he writes:

“Although strong emergence is logically possible, it is uncomfortably like magic. How does an irreducible but supervenient downward causal power arise, since by definition it cannot be due to the aggregation of the micro-level potentialities? Such causal powers would be quite unlike anything within our scientific ken. This not only indicates how they will discomfort reasonable forms of materialism. Their mysteriousness will only heighten the traditional worry that emergence entails illegitimately getting something from nothing.”

Sean Carroll on Strong Emergence

Sean Carroll offers us us a definition of strong emergence. He tells us that

“[i]n strong emergence... [w]hen many parts come together to make a whole, in this view, not only should we be on the lookout for new knowledge in the form of better ways to describe the system, but we should contemplate new behaviour".

He continues:

“In strong emergence, the behaviour of a system with many parts is not reducible to the aggregate behaviour of all those parts, even in principle.”

Yet if the emergent theory gives us “new knowledge”, and also shows us “new behaviour” (as Carroll puts it), then surely there must be new things (or new conditions) and therefore a new ontology too.

As an example of strong emergence, Carroll cites an example from condensed-matter physics:

“... condensed-matter physicists have long argued that we should think of emergent properties as truly new, not 'merely' smeared-out versions of some deeper description.”

As for a specific example:

“Everyone working on the problem [of high-temperature superconductors] believe that such materials are made out of ordinary atoms, obeying ordinary microscopic rules; knowing that has been of essentially zero help in guiding us toward an understanding of why high-temperature superconductivity happens at all.”

Clearly the words “truly new” mean that it's not simply a new (or different) way of looking at the same thing: it is a truly new thing (or condition) which is being discussed.

Carroll also obliquely mentions “downward causation” when it comes to emergent systems. Or, less explicitly, he mentions the causal effects of a whole (or a system) on its parts. Carroll uses the example of a person to do so when he writes:

“A strong emergentist will say: No, you can't do that [predict the behaviour of an atom in the skin on the tip of a finger]. That atom is part of you, a person, and you don't [predict the behaviour of that atom without understanding something about the bigger person-system. Knowing about the atom and its surroundings is not enough.”

Elsewhere Carroll states that downward causation is what happens when the

“behavior of the parts is actually caused by the state of the whole, in a way not interpretable as due to the parts themselves”.

Carroll again describes downward causation¹ when he says that

“there is an effect on that atom by the larger system of which it is a part – an effect that cannot be thought of as arising from all of the other atoms individually”.

We can accept that parts are affected by wholes/systems (or that wholes/ systems affect their parts). However, these wholes/systems may still be nothing over and above the sum of their parts. (Though here we're ignoring environmental or external effects on a whole or on a system.)²

Higher Level or Emergent Properties?

At many points when Carroll speaks of “emergent properties”³ one suspects that the words “higher-level properties” would work just as well. (Indeed Carroll himself interchanges these terms.) That is, perhaps it's the case that not all (or even any) higher-level properties need also be seen as emergent properties. Indeed, to a non-physicist, it may seem strange to class “temperature” and “density” as emergent properties (as Carroll does). Why not simply see them as simply higher-level properties? (This, admittedly, may be a difference which doesn't really make much of a difference.)

In one place Carroll cites hurricanes as an example (“just atoms in motion”). Not only that: he compares hurricanes to consciousness in that he concludes: “Why should we treat consciousness any differently?” However, isn't this a bad comparison? Surely a hurricane is perfect example of what's called “weak emergence”; whereas consciousness is often deemed to be a case of “strong emergence”.

Carroll makes a related point when he compares consciousness to water in terms of the latter's “phase transitions” (often also called “phase changes”). Firstly, we have water whose “molecular structure is [] rearranged” (i.e., to form liquid, ice and vapor). And then Carroll says something similar about consciousness.

Perhaps the problem here is Carroll's stance on reductionism. Take Francis Crick when he describes mentality in an often-quoted passage:

“'You', your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.”

Carroll too may misconstrue reductionism when he uses a phrase like “hurricanes are just atoms in motion” (which is like Crick's “are in fact no more than...”). (Hurricanes and water, in Carroll's accounts, can be seen as examples of weak emergence.) Elsewhere, he also says that we can think of ourselves as just “a collection of atoms”. The thing is, not many reductionists think of anything as just "a collection of atoms". They think of any x as a collection of certain types of atoms, forming certain kinds of molecules, forming certain kinds of configurations, forming certain kinds of systems which themselves exist in certain environments and interact with other systems... almost ad infinitum.

Carroll also asks us if

“there is something we learn from studying emergent level that we could not understand by studying the microscopic level”.

It can be said (at least at a prima facie level) that of course it must be believed that we can learn something new otherwise emergent theories would be deemed pointless. Thus, at least according emergentists, emergent theories must offer us something new - by definition. It's also the case the emergentists are bound to believe that “we'll learn more (and more quickly) by studying those higher levels themselves” (rather than “lower levels”).

Autonomous Emergent Theories?

Carroll's idea on the “autonomy” of emergent theories is a vital part of his “poetic naturalism”. He tells us that within the approach it's still the case that

“there is only one, unified, physical world, but many different ways of talking about it, each of which captures an element of reality”.

The obvious question to ask here is: How do we know if it's the same “element” described by a different theory or a different element entirely?

At a certain level, Carroll's position on emergent theories to some extent mirrors Ludwig Wittgenstein's doctrine of a “language game”. In Wittgenstein's case, language games are autonomous and play by their own rules (as it were). This, to Wittgenstein, had many important philosophical, moral and social consequences. The same appears to be the case with Carroll's position on emergent theories and his poetic naturalism.

Thus Carroll makes a lot of emergent theories being what he calls “autonomous”. He writes:

“The emergent theory is autonomous... it works by itself, without reference to other theories...”

Elsewhere, he says that with strong emergence “all stories are autonomous, even incompatible”.

However, in different places, Carroll also stresses emergent theories and their compatibility with non-emergent theories. Indeed Carroll hints at a lack of complete autonomy when he admits (if that's the right word) that “we might learn a little bit about higher levels by studying lower ones”.

It's nonetheless true that an emergent theory needn't explicitly (or even implicitly) refer to more fundamental/basic theories. However, surely it must still have various connections to them. In addition, if we refer back to Hedwig Wittgenstein's language games, why can't autonomous language games (even if they exist) include (or rely on) other language games. Indeed they do!

Carroll also emphasises the “mapping” of a fundamental theory onto an emergent theory in what he calls “course-graining”. Thus how can we have mapping as well as autonomy? Carroll gives the example of “an explicit map from one theory (molecules) to the other (fluid)”. (These are like the “bridge principles” - or “bridge laws” - formulated by philosophers.) Yet it's very clear that such course-graining (or bridge principles) are far less convincing or workable when it comes to mapping mental states to physical states then it is for Carroll's example of molecules and fluid. Indeed Carroll's example works from the fundamental theory (molecules) to the higher-level theory (fluid). Yet, in the philosophy of mind, philosophers have attempted to work the other way around: from mental states (higher-level states) to brain/neuronal states (lower-level states). That is, how easy is it also to map fluid (or states of fluid) to molecules (or systems of molecules) rather than the other way around?

So we must ask if an emergent theory can be truly autonomous. It can indeed be separate; though why also completely autonomous?

In addition, can “different ontologies” liv[e] happily alongside “the same underlying reality”, as Carroll argues? If not, then emergent theories, again, may not be completely autonomous. Indeed Carroll himself says that “emergence is about different theories speaking different languages”: not “deriving one theory from another”.

In a seminar Carroll also uses the word “consistence” in reference to the fit between emergent and more basic theories. Thus how can that consistency between two “autonomous” theories be established?

There are other problems here. Carroll says that an emergent theory can provide us with “an accurate description of the world within its domain of applicability”. Yet can an easier option be to simply say that it is the same domain which has different words, terms, concepts, senses and themes applied to it? This may simply depend, however, on how strongly (or widely) we take the word “domain” to be.

So who says the emergent theories are accurate? Does Carroll simply assume here an accuracy that's essentially guaranteed by the/a more fundamental/basic theory, thus limiting the emergent theory's supposed autonomy? Carroll also assumes compatibility between emergent theories and more fundamental (basic) theories.

Carroll talks about the ether theory. He says that it “served no empirical purpose”. That claim too assumes that a/the fundamental theory must have trumped the emergent theory. (That's if the ether theory was/is about emergence at all.) Surely both “empirical purpose” and accuracy can only be determined and guaranteed by fundamental/basic theories. Thus, again, the emergent theory can't be fully autonomous. (On a sidenote: the ether theory was deemed to “serve an empirical purpose” - at least at one point in scientific history.)

In addition, it simply isn't true that “different vocabularies” imply (or entail) “different ontologies”. At a very crude level, if someone uses the name the “Morning Star” and another person uses the name the “Evening Star”, and both persons know that both names refer to the planet Venus, then we don't have different ontologies on our hands here. Instead, different words, senses, technical terms, etc. can be seen to have the same ontology and therefore the “same underlying reality”. Ontology, after all, is often seen as what is, not as what we say about what is. Having said that, even an anti-realist can happily admit that different vocabularies don't necessarily imply (or entail) different ontologies.

There's also a problem with Carroll's assumption that if emergent theories can display what he calls a “useful role”, then that must automatically stop them from being “illusions”. Thus can we conclude (on Carroll's behalf) that consciousness, for example, plays a useful role and is therefore not an illusion?

What is a useful role anyway? And isn't it the case that on some interpretations illusions can indeed be useful? Can't “white lies”, for example, be useful?

So perhaps we can say that all this talk about “different stories” is really talk about about the practicality and simplicity (or the useful roles) of these emergent theories, rather than their meaty philosophical difference.

Notes:

1) I recently noted an exotic case of downward causation in the films Split and Glass directed by M. Night Shyamalan. In Split, for example, a psychiatrist said that her patients had “changed their biochemstry with their thoughts”. The result? They turned into supermen and superbeasts.

2) The biologist Peter Corning wrote:

"The debate about whether or not the whole can be predicted from the properties of the parts misses the point. Wholes produce unique combined effects, but many of these effects may be co-determined by the context and the interactions between the whole and its environment(s)."

3) Any x can only truly emerge if at one point there was no x and then x emerged from something which was not itself x. So surely that can't be the case with Carroll's examples of water. (Perhaps not even with consciousness.) Instead, as soon as you have a particular set of conditions (say, H2O molecules), then you have x (say, water). This means that x doesn't emerge from those conditions because those conditions never exist without there being the property x. Of course we needn't see emergence in this temporal manner (i.e., not-x, then x); though it's hard to see it otherwise.

Did Niels Bohr Go Too Far?

Perhaps there isn't enough written by Niels Bohr to secure a faithful interpretation of his philosophy of quantum physics. That's despite the fact that Bohr did say a lot more than many other physicists on philosophical issues.

In more precise terms, Bohr never published a paper on the philosophy of quantum mechanics. (Though, clearly, he published much on physics itself - sometimes with philosophical interjections.)That's not a surprise: Bohr was a physicist, not a philosopher. So, again, because of that lack of technical philosophical detail, and philosophical argument, it's no wonder that philosophers argue about what exactly Bohr's philosophical position was. It's also worth noting that many of his philosophical remarks on quantum mechanics came after he'd done his important and relevant work in physics. (His published philosophical positions came largely after the 1920s - and sometimes a lot later than that.)

Thus it may also seem odd that there are books on “Bohr's philosophy”. And we also have books actually of (rather than about) Bohr's philosophy - such as The Philosophical Writings of Niels Bohr (in three volumes). Nonetheless, the problems I've just highlighted are summed up by one reviewer of this book. He writes:

“Niels Bohr's view of the world is always something to keep in mind. But this book's title is misleading: if you're trying to understand how the (back then) new discoveries and theories in physics may have affected and /or influenced Niels Bohr from a non-theoretical, philosophical point of view, you won't find it here.”

To sum up Bohr's philosophical position. I would say that “subjectivist” is a far better term than “idealist” to sum up Bohr's philosophy of quantum physics. And, in turn, “anti-realist” is far better than “subjectivist”. The term “idealism”, for one, comes with far too much philosophical and historical baggage to affix it to Bohr's positions. In addition, it's clear that Bohr fused subjectivism with intersubjectivism. (The latter position is something that the logical positivist Rudolf Carnap had to take on board in order to escape from the possible “solipsism” of his 1928 Aufbau position.) Indeed, as a physicist, Bohr could hardly not have fused subjectivism and intersubjectivism.

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i) Niels Bohr's Ant-Realism?

Although I'm shoehorning terms from late-20th-century analytic philosophy into physics here, it can be said that Niels Bohr perfectly expressed an anti-realist position on physics (without ever actually using the term “anti-realism”) in the following:

“Physics is not about how the world is, it is about what we can say about the world.”

And in his The Unity of Human Knowledge (1958-1962), Bohr offers us a slightly more detailed anti-realist account of physics:

“Physics is to be regarded not so much as the study of something a priori given, but rather as the development of methods of ordering and surveying human experience.”

Of course Bohr wasn't alone. For example, the Swiss-American theoretical physicist, Wolfgang Pauli, went further when he rejected the opposition (i.e., between reality itself and what we can can know about reality) entirely when he stated the following (as quoted by N. David Mermin):

“One should no more rack one's brain about the problem of whether something one cannot know anything about exists all the same, than about the ancient question of how many angels are able to sit on the point of a needle.”

In other words, “how Nature is” amounts to no more than a metaphysician's dream. All we have is “what we can say about Nature”. And, at the quantum-mechanical level, what we can say is what we can say with mathematics. Consequently, just about everything else is analogical and/or imagistic. Indeed the analogical stuff can (or does) often mislead us. And perhaps that's also partly the source of quantum mechanic's "weirdness".

Despite all that, the quotes above don't in any way suggest that (as the philosopher Michael J. Loux puts it about idealism and anti-realism) physicists will “we make it all up”. (Or, as some say about postmodernism, that “anything goes”.) And neither does it commit physicists to idealism. What it does tell us is that we don't have something “a priori given”: what is given is mediated through “human experience”. How can it be otherwise? Nonetheless, not all of this need to be entirely “subjective” either - it is often intersubjective. As Bohr himself puts it:

“In this respect our task must be to account for such experience in a manner independent of individual subjective judgement and therefore objective in the sense that it can be unambiguously communicated in ordinary human language.”

This means that even if a multitude of different minds come to state various things about x, they're still (at least roughly) saying similar things about x. So, yes, minds matter. But that doesn't mean that anything goes or that physicists make it all up. After all, if a multitude of minds agree that the earth isn't flat, then surely that doesn't also mean that all those minds make that fact up.

It's true that Niels Bohr did seem to argue that our experimental results didn't reflect a reality which existed independently of our measurements. Yet surely if there were a different reality, then there would be different results. This isn't of course to say that there's a perfect mirroring of that reality with our results. Though there is a mind-independent reality which somehow determines or causes our experimental results. This, of course, isn't the claim that our theories or terms perfectly mirror (or mirror at all) that mind-independent reality. The claim is very simple and somewhat obvious: the mind-independent world can't be factored out.

So Bohr was wrong to say that nothing exists until it is measured. However, in a strong sense, it may as well not do. That is, we can say very little about that x as it is before it's measured or experimented upon. In that sense, it serves almost no purpose. Yet it still has causal effects on what we say. It's still an x which has specific results on our experiments and measurements. Thus if that x were substituted with y, then we'd have different experimental results and different measurements. In that sense, the noumenon (to use a Kantian term) that is x is obviously of vital importance.

In the same vain. Simply because our measurements and experiments produce changes in what's been measured, that doesn't also mean that what's been measured is somehow factored out. And neither does it mean that there's no relation between what's being measured and what we say about what's being measured. Again, there will be no perfect mirroring because such a notion hardly makes sense. However, there may be very strong relations between what we say and what we measure. Those relations may be symmetrical, isomorphic, etc. in nature. There may also be various correspondences (though not mirrorings) or modelings of various kinds.

Bohr himself went further and into detail on this.

For example, he claimed that the spin of an electron or the momentum of an atom aren't things which reflect what is the case mind-independently. It's true that there's (obviously) some level of contingency in our descriptions and experimental results. However, the fact that physicists have stuck with words like “spin” and “momentum” (as well as the precise measurements of spin and momentum) must mean that they're getting at least something right.

Bohr also gave an explicitly anti-essentialist position when he said that

“our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, as far as possible, relations between the manifold aspects of our experience”.

Nonetheless, Bohr does (again) seem to needlessly play down the world and, correspondingly, play up mind or “our experience”.

For one, we can deny “real essence” yet also play down the idealist, subjectivist or phenomenalist implications of Bohr's words. After all, when it comes to elementary particles, the distinction between essential and contingent properties is hard to maintain in the sense that besides spatial, temporal and relational properties, properties such as spin, mass and energy are the only properties particles have. So, for example, when you give the spin or mass of an electron, you're not factoring out a whole host of contingent properties of that electron in one's descriptions.

The subjectivist import of Bohr's words is also apparent when he said that we

“only to track down, as far as possible, relations between the manifold aspects of our experience".

Why not say, instead, that we should track down the relations between the “manifold aspects of experience” and what (causally) gives rise to that experience? It's true that this is a difficult ontological and epistemological nut to crack. However, it's a nut which exists. Thus if it's literally all about the manifold aspects of our experiences, then why talk about “experiments”, “observations” or “electrons” at all? Why not give a purely phenomenological account of the specific experiences of physicists at particular times? Indeed why single out what physicists say in the first place – why not ask sociologists or fishermen?

Subjectivism vs. Intersubjectivism

Despite all the above, Bohr himself notes the problem with over-stressing what he calls the “subjective element”. Or at least he does so when it came to Albert Einstein's relativity theory. Here is an example:

“Today we know that 'simultaneity' contains a subjective element, inasmuch as two events that appear simultaneous to an observer at rest are not necessarily simultaneous to an observer in motion.”

The above is the “subjective element”. What follows is what we can call the intersubjective element of exactly the same situation:

“However, the relativistic description is also objective inasmuch as every observer can deduce by calculation what the other observer will perceive or has perceived.”

Still, Bohr ends on a non-classical note when he says that

“[f]or all that, we have come a long way from the classical ideal of objective descriptions”.

And Bohr makes roughly the same point elsewhere when he says that

“every physical process may be said to have objective and subjective features”.

He continued:

“Admittedly, even in our future encounters with reality we shall have to distinguish between the objective and the subjective side, to make a division between the two. But the location of the separation may depend on the way things are looked at; to a certain extent it can be chosen at will.”

To put all that in more basic terms: it's clear that Bohr's position (or positions) could never be deemed to be entirely subjectivist. Indeed isn't that obvious? Though, as we can see in the quotes above, there is indeed an element of subjectivism (or experientialism) in Bohr's statements.

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ii) The Case of Waves & Particles

As Bohr put it, the words “wave” and “particle” are “classical terms”:

“However far the phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms.”

Bohr extends what he says about classical terms and refers to “what we have done” in our “experiments”. He wrote:

“The argument is that simply by the word 'experiment' we refer to a situation where we can tell others what we have done and what we have learned and that, therefore, the account of the experimental arrangement and of the results of the observations must be expressed in unambiguous language with suitable application of the terminology of classical physics.”

In a certain sense, we have nothing more than classical terms because even when we attempt to describe the “strange” goings-on of the quantum world, we still use classical terms. Why? Because there's nothing else we can use other than the mathematics.

Mathematics has just been mentioned. Bohr makes it clear that only mathematics gives us a true of picture of the quantum realm. He wrote:

"We must be clear that when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections.”

This, again, is a roundabout of saying that only the mathematics is adequate when it comes to describing sub-atomic phenomena. Thus, by this definition, the words “particle” and “wave” simply can't do the full job. They can do part of the job; though not the full job. Indeed it's not just the word “particle” that's problematic, thinking of particles as things is too. Bohr wote:

"Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems."

In other words, it can't possibly be about the world “as it is in itself”. Every statement we make about the world comes with a lot of contingent baggage. There is of course a causal set of relations to any x – though those very same relations can be described in an indefinite number of ways.

So when Louis de Broglie argued (in 1924) that that every moving particle (yes, particle) can be equally described as either a wave or a particle, that may well be because this x is neither a wave or a particle. Nonetheless, describing x as a wave or a particle still helps both physicists and ourselves.

It's also the case that the words “particle” and “wave” carry far too much baggage. After all, the original wave-particle experiments had water waves in mind. Is that a good thing when it comes to talk about things happening at the subatomic level? Yes, it is if it helps us get of grip of things. The same goes for the word “particle”. Thus there are a host of good reasons as to why x should be seen as a particle. Yet there are also a host of equally good reasons as to why we shouldn't see it as a particle.

For instance, is a photon a particle? Well, they don't have mass for a start. And that's partly why the physicist Willis Lamb said:

“At the first of the 1960's Rochester Coherence Conferences, I suggested that a license be required for use of the word photon, and offered to give such license to properly qualified people.”

Lamb then went on to say that “[t]here are very good substitute words for 'photon' (e.g., 'radiation' or 'light')”.

Bohr himself argued that the reality behind our measurements and experiments is that there is neither a particle nor a wave. Indeed linguistic practicalities led me to want to say: The reality behind the particle/wave measurements and experiments is that there is neither a particle nor a wave. But we must still talk about something. However, that something isn't necessarily a thing as such (this is grammar speaking here). And we give that x (which doesn't need to be a thing, only a something) the name “wave” or “particle”.

Michael J. Loux's Metaphysical Realism: Beyond Concepts and Representations

Michael J. Loux assumes that the “conceptual schemer” (as he calls him) won't have realised that his own concepts (or his own conceptual scheme) will need to be applied to

“the conceptual schemer's account of conceptual representation”.

Loux sees this as being self-defeating on the conceptual schemer's part.

Simply because this may be (or is) the case, that doesn't also mean that there's nothing to account for. Neither does it mean that “we make it all up”. (This is how Loux describes “subjective idealism”, which he ties to anti-realism - as does fellow metaphysical realist, Peter van Inwagen.)

It's obviously true that a conceptual schemer can't have a metaphysically-realist position on his own conceptual scheme itself: that would indeed be somewhat self-defeating or even self-contradictory. However, if he doesn't accept metaphysical realism for an account of the world, then why should he accept it for an account of his own conceptual scheme? Instead, he'll apply the same logic to conceptual schemes as he does to the world. And that doesn't mean that he makes it all up or that “anything goes”. There's still a conceptual scheme to account for: even if meta-concepts or second-order concepts (as it were) are required for such an account.

The problem here is that metaphysical realist (or Michael Loux) simply assumes that

“conceptual representation bars us from an apprehension of anything we seek to represent” .

That's not the case. Do the theories and models of physics deny physicists an apprehension of anything they seek to describe, understand or represent? 

The metaphysical realist makes the same mistake when it comes to the nature of the world (i.e., regardless of conceptual schemes). He assumes that anything other than a thoroughly metaphysically-realist position (or position from within “traditional metaphysics”) will bar us from an apprehension of anything we seek to represent. However, anti-realists are representing something – something which has a causal affect on us. Despite that, there are many reasons for believing that we can't get that something in its pristine state. That something is causally responsible for our statements, theories, experiences, sense-events and models. However, that same something can bring about many different statements, experiences, sense-events, theories and models. And that's partly because of the mediation of various contingent factors: mind, language, concepts, prior theories and whatnot.

So it doesn't follow that we don't “get[] hold” of our conceptual scheme of the world simply because we don't get hold of the world itself. That's because getting hold of the world itself (i.e., with the mind alone) hardly makes philosophical or logical sense.

Peter van Inwagen's Extreme Metaphysical Realism

Peter van Inwagen is an American philosopher and John Cardinal O'Hara Professor of Philosophy at the University of Notre Dame. He was also the president of the Society of Christian Philosophers from 2010 to 2013.

Van Inwagen has been a major player in the debate about free will. He introduced the term 'incompatibilism' to stress the position that free will is not compatible with determinism. Van Inwagen has also taken part in the “afterlife debate”. (He wrote a piece called 'I Look for the Resurrection of the Dead and the Life of the World to Come'.) 

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The following piece is primarily a commentary on the 'Objectivity' chapter of Peter van Inwagen's book Metaphysics. 

Orwellian

Perhaps the final paragraph of Peter van Inwagen's chapter 'Objectivity' is what motivated him to adumbrate his positions against anti-realism. He writes:

“Before we leave the topic of Realism and anti-Realism, however, I should like to direct the reader’s attention to the greatest of all attacks on anti-Realism, George Orwell's novel 1984. Anyone who is interested in Realism and anti-Realism should be steeped in the message of this book. The reader is particularly directed to the debate between the Realist Winston Smith and the anti-Realist O’Brien that is the climax of the novel. In the end, there is only one question that can be addressed to the anti-Realist: How does your position differ from O’Brien’s?”

Does van Inwagen see anti-realism as some kind of postmodernist fashion designed to let “anything go”? Or perhaps he sees anti-realism as advancing various political projects (i.e., instead of truth). Another fact (rather than possibility) is that van Inwagen sees idealism as being indistinguishable from anti-realism when it comes to what really matters philosophically. Michael J. Loux (van Inwagen's fellow University of Notre Dame-based metaphysical realist) also sees “subjective idealism” as “the view that we make it all up”. 

If we get back to the van Inwagen passage above. 

Winston Smith is not a realist. Or, rather, he's neither a realist nor an anti-realist. That's because the dispute between anti-realism and realism is largely a 20th century phenomenon within the domain of Anglo-American analytic philosophy.

In addition, anti-realists don't necessarily have specific positions on politics or on anything else (i.e., other than on anti-realism and its relation to realism). Anti-realism can of course be applied to other subjects; though it's not necessarily tied to any other subject. Not only that: it's often said that anti-realists can be anti-realists in one domain and not in other domains. And even when anti-realists do apply anti-realist ideas to a particular domain, they still say different things about other domains.

Metaphysics

It's clear that van Inwagen's take on anti-realism and realism is largely motivated by his position on metaphysics itself.  In his paper, 'The Nature of Metaphysics', he writes:

“We might say that one is engaged in 'metaphysics' if one is attempting to get behind all appearances and describe things as they really are.”

Van Inwagen's definition also ties in with other realist definitions of metaphysics. Take Michael J. Loux again, who tells us that

“[W]e [realists] can, in good conscience, go on believing in a mind-independent reality and go on as well believing that metaphysics gives us access to the nature of being qua being”.

If we concentrate on van Inwagen, it can be said that just as van Inwagen defines the words “objective truth”, “anti-realism” and even “realism” itself in his own individual way (as will be seen later), so too does he do the same with the word “metaphysics”. 

For a start, even if there are philosophers who deny that we can “get behind all appearances” (or whom reject the very notion of appearances), can't we say that they're still doing metaphysics? More importantly, the final clause  (i.e, “describe things as they really are”) begs the question against anti-realism. Thus, from the beginning and even before any analysis/debate begins, van Inwagen is saying that anti-realists (as well as idealists, phenomenalists, Kantians, etc.) can't actually be metaphysicians. Why? It's because they aren't realists in the manner in which van Inwagen himself is a realist.

Van Inwagen also tells us that  

“metaphysics is the attempt to discover the nature of ultimate reality”.

Thus if one doesn't accept that definition (or if one questions the term “ultimate reality”), then one can't be doing metaphysics at all! So it's not a surprise that Inwagen also says the following: 

“It is therefore misleading to think of anti-Realism as a metaphysics... Anti-Realism, rather, is a denial of the possibility of metaphysics...”

It's true that anti-realists emphasise their epistemological approach to metaphysics. Yet that's still an approach to metaphysics. It isn't automatically a denial of the possibility or existence of metaphysics. Or, rather, it is if one accepts van Inwagen's position in full. Indeed it seems that one has to accept van Inwagen's position in full if one wants to continue doing metaphysics. 

Here again van Inwagen assumes that there is only one definition of both “realism” and “metaphysics”:

“And Realism is a metaphysics only in the sense that it is a thesis that is common to all metaphysical theories.”

To repeat: if one doesn't abide by van Inwagen's take on both realism and anti-realism (as well as his take on metaphysics itself), then one can't be doing metaphysics at all. 

Ultimate Reality and Mind-Independence?

Does anyone really know what the word “ultimate” means in the context of the often-used phrase “ultimate reality”? 

Van Inwagen, for one, tells us that 

“there is such a thing as ultimate reality, a reality that lies behind all appearances”. 

Now even if the word “ultimate” simply means reality as it is regardless of minds, we can still ask why the word “ultimate” has been used. 

In addition, many anti-realists will say that even if there is a reality that “lies behind appearances”, we can still never know what that reality is (or what it's like). So why use the adjective “ultimate” at all? Can x be an ultimate anything if it can never be known, seen, experienced or whistled? And how, exactly, does reality “lie behind” anything? What does it mean for reality to lie behind appearances? Indeed it can't it be said that appearances also belong to reality? What else can appearances belong to?

Van Inwagen is also most certainly wrong when he claims that the “anti-realists say that nothing is independent of the mind”. Or, at the very least, I can't imagine any anti-realist making that claim. Van Inwagen writes:

“The anti-realist who says that nothing is independent of the mind, however, really does mean something very much like this: the collective activity of all minds is somehow determinative of the general nature of reality.” 

As stated, I don't suppose for one second that most (or even any) anti-realists believe that “nothing is independent of the mind”. There are lots of things which are independent of the mind. However, once we speak of them, describe them, or have knowledge of them, then they become (by definition) dependent on minds. These things aren't literally created by minds - though they do come to be known or experienced by minds. 

Objective Truth

It's strange that van Inwagen takes the term 'objective truth' literally in that he says 

“our beliefs and assertions is therefore 'objective' in the sense that truth and falsity are conferred on those beliefs and assertions by their objects, by the things they are about”.

Of course no one would doubt or deny that statement S is about the things it is about. The problem is how we make philosophical sense of that claim.

Van Inwagen also assumes too much when he talks about what he calls “objective truth”. 

Firstly he tells us exactly what he takes objective truth to be. And then he says that when his definition is rejected or denied, then objective truth is automatically rejected or denied too. Yet we needn't accept van Inwagen's take on objective truth.

Van Inwagen tells us that 

“those statements would be objectively true that correctly described the ultimate or context-independent reality”.

In other words, van Inwagen is telling us that we have to accept both ultimate reality (as well as his philosophical take of it) and context independence before we can claim objective truth. However, that isn't a logical claim. It's not an epistemological or metaphysical claim either. Instead, it has all the hallmarks of a stipulative definition of the two words “objective truth”. A philosopher can easily argue that objective truth has nothing to do with “ultimate reality” or “context independence”. Sure, he'd need to argue his case and perhaps his arguments wouldn't be very convincing. However, this option is on the table; yet van Inwagen seems to assume that it simply doesn't even exist. 

Take just one example. Hartry Field has written an entire book called Truth and the Absence of Fact; as well as a paper called 'Mathematical Objectivity and Mathematical Objects' (in which mathematical objects are denied or rejected). Now Hartry Field's arguments may be airtight or they may be rubbish. But at least his option is in the marketplace. And there are many other similar options in the marketplace too.

We can go into more detail here. 

How would we know that statements “correctly described the ultimate or context-independent reality”? This too makes an obvious assumption. In order to know that our statements correctly describe ultimate reality, we'd already need to know ultimate reality in order to be sure that the matches between our statements and ultimate reality are correct. We'd also need to explain how statements (as bits of a natural language) could match things that aren't themselves statements (or bits of a natural language). In addition, does the tie between true statements about ultimate reality itself also partake in ultimate reality? For example, is the correspondence between the statement “Snow is white” and snow's being white itself an aspect of ultimate reality? What's more, do natural-language statements about ultimate reality themselves belong to “appearances”? And if not, why not?

As for context-independent reality: how can we gain access to it? What does it look like? Or, perhaps more correctly, what is it like? Can a context-free reality even be described or whistled?

Mount Everest

Van Inwagen puts the realist case in the simplest terms by invoking the nature of Mount Everest. He writes:

“.... if there had never been any intelligent beings on the earth, Mount Everest would, despite the absence of intelligence from the terrestrial scene, have exactly the size and shape it has in fact.” 

We can accept (provisionally) that Mount Everest would have “exactly the size and shape it has [] if there had never been any intelligent beings on the earth”. But what does that claim amount to? Van Inwagen is saying: 

Whatever x is, x will be as x is regardless of human minds. 

But that's to say very little. Almost nothing. All we have is what people have said about Mount Everest. The claim that minds don't change the nature of Mount Everest doesn't get us anywhere. It doesn't get us anywhere practically. More relevantly, it doesn't get us anywhere philosophically either. It's a claim that has very little substance. Despite that, it purports to tell us something profound about the force of metaphysical realism. 

So an anti-realist doesn't need to deny that any x is “entirely independent of all human mental activity”. However, he does have a problem with the prefixed statement: “the fact F is entirely independent of all human mental activity”. That's because it includes the predicate symbol F and also uses the word “fact”. It makes little sense to say that facts are “mind-independent”. 

It's certainly true that many philosophers have deemed propositions, universals and numbers to be mind-independent. However, there aren't many who've believed that facts are mind-independent too. Van Inwagen does. He writes:

“If there were no beings with minds, there would be no one to observe or grasp or be aware of this fact, but the fact would still be there.”

So, in this context, van Inwagen believes that the world is cut up into “sentence-shaped objects”, as Peter Strawson once put it. That means that not only is the mind-independence of the world important to van Inwagen, so too are the many (or infinite) sentence-shaped chunks of the world - those bits which precisely match true statements.

Yet x doesn't tell us what to say about it. However, we can state the following:

x [an obviously unquantified variable, in this case] is how it is regardless of minds. 

But what is x? -

x is independent of minds. What we say about x isn't.

Thus x's ontological purity is “collapsed” (to steal a word from quantum mechanics) by minds once things are said about it. Or, to use Kantian phraseology, when x is talked about, it immediately moves from being a noumenon to being a phenomenon.

Idealism

Van Inwagen also conflates idealism with anti-realism. 

Firstly, he asks the following question:

“Is not idealism essentially the thesis that there is no mind-independent world 'out there' for our sensations to be correct or incorrect representations of?”

And then he asks:

“And is not anti-realism the thesis that there is no mind-independent world 'out there' for our sensations to be true or false statements about?"

Idealism and anti-realism are very different. Despite what van Inwagen says, anti-realism does not state that there is no mind-independent world “out there for our sensations to be true or false about”. It says that there is one; and it's causally responsible for our sensations and our true and false statements. However, as it is “in itself” (i.e., in its mind-independent state) is of no meaning or purpose. It's a difference which quite literally doesn't make difference.

Donald Davidson (not usually deemed to be an anti-realist) summed up this position very well. However, in the following passage (from his paper 'A Coherence Theory of Truth and Knowledge') he talked primarily about “belief” and “sensation”, not about statements and the mind-independent world. He wrote:

“The relation between a sensation and a belief cannot be logical. Since sensations are not beliefs or other propositional attitudes. What then is the relation? The answer is, I think, obvious: the relation is causal. Sensations cause some beliefs and in this sense are the basis or ground of those beliefs. But a causal explanation of belief does not show how or why the belief is justified.” 

So it's worth rewriting this passage for clarification and putting it within the context of anti-realism and realism. Thus:

The relation between true or false statements and a mind-independent world cannot be logical. Since true or false statements are not the mind-independent world. What then is the relation? The answer is, I think, obvious: the relation is causal. The mind-independent world causes some true or false statements and in this sense are the basis or ground of those true or false statements. But a causal explanation of true or false statements doesn't show how or why those statements are true or false of the mind-independent world.

As hinted at, it can't be said that this rewriting works in all respects. That's primarily because Davidson was talking about the justification of beliefs, not the relation of statements to the world. Nonetheless, the form of the argument still stands and the central point about causation does too.

Another passage from the same paper by Davidson is even more apposite in this context. He wrote:

“Accordingly, I suggest that we give up the idea that meaning or knowledge is grounded on something that counts as an ultimate source of evidence. No doubt meaning and knowledge depend on experience, and experience ultimately on sensation. But this is the 'depend' of causality, not of evidence or justification.” 

Here again we can rewrite Davidson in the context of van Inwagen's take on realism and anti-realism. Thus:

I suggest that we give up the idea that true or false statements are grounded on something that counts as an ultimate reality. No doubt true or false statements ultimately depend on the mind-independent world. But this is the 'depend' of causality, not mind-independent truth or fact.

So, to repeat, anti-realists don't reject a mind-independent world (though some brands of idealism do). Instead, anti-realists simply has a different take on the mind-independent world. In Davidson's terms, many of our true and false statements causally “depend” on that mind-independent world. However, that mind-independent world doesn't and can't in and of itself guarantee us truth.

Bishop Berkeley

Since we've just discussed idealism, it's worth commenting on something else that van Inwagen writes in this respect.

Van Inwagen offers us an “argument without force” to show us that anti-realism fails.  His argument is about “form[ing] an image” of an event which “no one is observing”. He states:

“Isn’t it [the anti-realist position] like saying that a painter can never paint a picture of someone who is alone, since any attempt to do so represents the figure in the painting as being observed by someone who is occupying a certain point of view—the point of view that the viewer of the painting is invited, in imagination, to share?”

Firstly, van Inwagen simply assumes that the position above is wrong without actually saying why. What he appears to be saying is that since the person painted is painted as being alone, then the actual painting itself must somehow represent that person's genuine aloneness. In other words, the subject has been painted form literally no “point of view”. But clearly all paintings of people ostensibly on their own are painted from a point of view. There's not even a possibility of painting a lone person from no point of view – not even conceivably (except, perhaps, in some very abstract piece).

Thus Bishop Berkeley was perfectly justified (at least at first) in stating the following:

"But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park... and nobody by to perceive them... The objects of sense exist only when they are perceived; the trees therefore are in the garden... no longer than while there is somebody by to perceive them."

So when one imagines a tree (or person to be painted) without anyone looking at it, one actually imagines someone looking at a tree (or looking at the person to be painted) – except that the observer (or painter) isn't supposed to be there. 

Now of course realists, anti-realists or idealists/phenomenalists don't need to rely on this argument about our imaginative limitations to establish their positions. Nonetheless, Berkeley was still at least partly justified in saying what he said.

Despite that, van Inwagen may be correct to argue that “mind-independence [] does not require those to whom the argument is addressed form a mental image”. That's certainly the case if one is talking about “unobserved geological processes”. But it doesn't follow from this that what's been said also applies to a painter painting a supposedly unobserved person. Nonetheless, if mental images are out of the question for ancient geological processes, then so too are “certain verbal descriptions of those [geological[ processes”. That's because even without mental imagery, verbal descriptions are still at least partly – as well as obviously - a result of minds. Regardless of mental images, those descriptions will include contingent natural-language words, concepts, and whatnot. To put that another way: these seemingly mind-independent geological processes could be described in other ways – indeed in an infinite number of other ways!

Self-Referential Self-Destruction?

Van Inwagen attempts to sum of the anti-realist position in a single slogan. This:

“Objective truth and falsity do not exist.”

You can see what's coming now. What we have here is a self-referential self-destruction... Or so it seems. Van Inwagen continues:

“[The above] is a statement about all statements, and it is therefore a statement about itself. What does it say about itself? Well, just what it says about all other statements: that it is neither objectively true nor objectively false. And, of course, it follows from this that it is not objectively true. If it is not objectively true, if it is not true in virtue of corresponding to a reality that is independent of human mental activity, what is it - according to the anti-Realists? What status do they accord to it?”

Van Inwagen made exactly the same argument (in another article) about the position advanced by logical positivist at one point in the 1930s. Firstly he expresses their position thus:

“The meaning of a statement consists entirely in the predictions it makes about possible experience.” 

And then van Inwagen gleefully notes its self-referential flaws:

“Does this statement make any predictions about possible experiences? Could some observation show that this statement is true?... It would seem not... And, therefore, if the statement is true it is meaningless; or, what is the same thing, if it is meaningful, it is false.” 

Let's stick to anti-realism. 

Van Inwagen assumes that anti-realists deny or reject objective truth. Not all of them do. He also assumes that everyone must accept his own definition of the words “objective truth”. This is problematic because if they do so, then van Inwagen's conclusions about self-referential self-destruction would indeed be correct. So, again, anti-realist needn't deny the notion of objective truth and they certainly don't need to accept van Inwagen's own personal definition of what constitutes objective truth.

The other problem with van Inwagen's analysis is that even if anti-realists accepted the statement “objective truth and falsity do not exist”, what van Inwagen says about this statement may not be the case. Anti-realists could take the statement “objective truth and falsity do not exist” as a second-order (or a meta) statement. Either that or as a principle (normative or otherwise). In other words, it's a statement about statements, not a metaphysical statement. That is, it's not a statement about the nature of the world: it's a statement about statements about the world. Another way of putting that is to say that it's an epistemological take on statements about the world.

The failure to make this kind of distinction is summed up by the science journalist John Horgan when he recalls an interview with Karl Popper. He writes:

“'The first thing you do in a philosophy seminar when somebody proposes an idea is to say it doesn't satisfy its own criteria. It is one of the most idiotic criticisms one can image!'... Falsification itself is 'decidedly unempirical'; it belongs not to science but to philosophy, or 'metascience', and it does not apply to all science. Popper was admitting... that his critics were right: falsification is a mere guideline, a rule of thumb, sometimes helpful and sometimes not.” 

Conclusion

Peter van Inwagen isn't very fair to anti-realists - and that's apart from the fact that he never quotes a single one of them. Nor does he paraphrase particular arguments (or statements) from any anti-realists. (Though he does quote his very own fictional anti-realist.) Instead, he tells us what he thinks anti-realists believe. More importantly:

i) Peter van Inwagen misrepresents the positions of most anti-realists. 

ii) He at least partly conflates anti-realism with idealism. 

iii) And he defines terms such as “metaphysics”, “objective truth” and "anti-realism" in such a way that renders all his opponents straw targets or self-contradictory. 

Finally, van Inwagen assumes that ant-realism is a much wider philosophy than it actually is.