1.1 What is Physicalism?
The problem of consciousness is special. We have intimate knowledge of it. Writers and thinkers have spent vast efforts in outlining its structure, capabilities and forms, in fiction, science and philosophy. Spectacular advances have been made in recent times in our ability to correlate brain processes with various kinds of conscious experiences. We can now tell, with high reliability, whether someone is conscious or not by using MRI brain imaging, even if the subject has been diagnosed as being in a vegetative state and gives no behavioural signs of anything but profound coma (see Owen 2008). Of course, we do not have a detailed account of how or where consciousness resides in the brain nor any such account of exactly what systems within the brain consciousness particularly or specifically depends upon.1 But nor do we have such accounts of any mental functions as yet, be they conscious or unconscious. The brain is vastly complicated and our investigations can still only be called preliminary but they are proceeding apace. We are truly on the way to finding out everything about consciousness that science can tell us.
Yet the problem of consciousness is special. It is the spectre haunting the scientific view of the world. The fear is that science cannot tell us everything there is to know about consciousness. This would be in conflict with an otherwise very attractive view of the world whose success has been spectacularly extensive and cumulative over the last half millennium.
This book is not directly about this view â called âmaterialismâ or, more accurately, âphysicalismâ, which is a philosophical interpretation of the success of physical science. The literature on physicalism: its nature, commitments, strengths and problems is staggeringly vast. In this book I do not aim to add anything definitive to this particular body of work in the way of settling any of these issues. But physicalism will loom large in the background since virtually all the philosophical theories of consciousness to be considered were formulated with at least one eye on the question of how to integrate consciousness into a physicalist account of the world. Some others to be considered result from a perceived failure of physicalism but even they must respect the scope and power of the physicalist world view.
It is important, then, to begin with an overview of the metaphysical problem of consciousness which puts in place the nature and goals of physicalism and highlights how consciousness generates a unique problem for it. This is a daunting task, but since we require here only a birdâs eye view, and since that will be more than sufficient to show why the problem of consciousness is special, the task is approachable. Beyond characterizing physicalism, the main issue to consider is why physicalism is favoured amongst so many and to ask whether its favoured status is really justified.
Physicalism is a monistic metaphysics: it claims that there is only one basic kind of reality which is physical in nature. However, the nature of the physical is another very vexed philosophical issue (see e.g. Montero 2009, Strawson 2006, Stoljar 2001, Howell 2013, pt. 1, Wilson 2006). I think physical reality is known in the first instance by ostension: we are in perceptual contact with aspects of the world which are paradigmatically physical. We begin there. But if known by ostension, the physical is revealed by science, most intimately by the foundational science of physics. Perceptually schooled naive intuition suggests a picture in which the physical is continuously extended, space filling and exclusively space occupying stuff. Unfortunately for intuition, science has revealed that the physical is much stranger than that and, so to speak, much less âmaterialâ. This means that we must take a somewhat provisional attitude to the question and characterize the physical as whatever physics describes, or will end up describing, as underlying the ostensively (and ostensibly) familiar physical world. But the oddity of the physical as revealed by science also means there is serious difficulty understanding the relation between the physical as scientifically revealed and the familiar aspects of the observable world which beget the notion of the physical in the first place. This is a viciously hard problem in detail (see Belot and Earman 1997).
The problem is unavoidable though for, clearly, not everything is physical in the scientific sense under its usual description. On the face of things, innumerable features of the world are not obviously physical. Quite to the contrary, the physical is fundamentally non-chemical, non-biological, non-geological, non-meteorological, non-mental, non-social, non-economic, non-political, etc. So, even if we grant that physics will eventually provide a comprehensive, complete and accurate account of physical reality, which is, for physicalists, all of reality, there will still need to be told a tale which relates the non-fundamentally physical to the fundamentally physical.
Thus one can envision a grand view of the world which begins with the world as described by fundamental physics and ends with all the features we are familiar with in both ordinary experience and all the non-fundamental sciences. To a remarkable extent, we have this view already in our grasp (see chs. 1â3 of Seager 2012 for a brief overview). There are untold numbers of known interconnections from the fundamental level to various non-fundamental features of our world which have been identified and explored. Looking at things from the reverse point of view, there are equally vast numbers of âanchor pointsâ where we can see, at least in general terms, how the non-fundamental springs from and depends upon the fundamental level. Any place where we do not yet see such interconnections or anchor points is a sore point, like a nagging splinter, but there remain very few such problematic areas.
It is easy to find working physicists who espouse this grand view. For example, the well-known string theorist and science popularizer Brian Greene believes that any âphysical system is completely determined by the arrangement of its particlesâ (2011, p. 38). This is not to be read as a mere definition of âphysical systemâ which leaves open whether there are non-physical systems lurking in reality, for Greene explicitly avows what he calls the âreductionist viewâ which he notes is âcommon among physicistsâ. He elaborates that âthe position that makes the most sense to me is that oneâs physical and mental characteristics are nothing but a manifestation of how the particles in oneâs body are arrangedâ (2011, p. 39). Even physicists such as Philip Anderson, famous for his anti-reductionism, does not dispute the sort of reductionism outlined by Greene. In his article, âMore is Differentâ, Anderson begins with the clarification that:
The reductionist hypothesis may still be a topic for controversy among philosophers, but among the great majority of active scientists I think it is accepted without question. The workings of our minds and bodies, and of all the animate or inanimate matter of which we have any detailed knowledge, are assumed to be controlled by the same set of fundamental laws âŚ
(1972, p. 393)
In the abstract, physicalism thus demands that there be a dependence (or determination) relation of the non-fundamental upon the fundamental. In order to sustain the claim of monism, this relation has to be pretty strong in at least two ways: logically and ontologically. As to the first, the dependence relation must be of maximal logical strength: physicalism requires that it be absolutely impossible for two worlds to be identical with respect to the properties, laws and arrangement of the physical fundamentals and yet differ with respect to anything else. The basic form of this relation is that of logical supervenience.
The concept of supervenience has become a complex topic in philosophy over the last 40 years or so, since it was reintroduced into the philosophersâ arsenal by Donald Davidson (1970; for an overview see McLaughlin and Bennett 2008). For our purposes, it is enough to understand logical supervenience as asserting that for any non-fundamental property, there are fundamental physical conditions which absolutely guarantee its instantiation. If you duplicate these physical conditions you will get a new instance of the property in question. And if you want to alter the distribution of the property in question, then you must make some change in the relevant fundamental physical conditions. Note that a claim of supervenience does not entail any claims about explicability. It is, so to speak, a purely metaphysical relation which asserts the determination of the non-fundamental by the fundamental but does not venture to say how the determination comes about.
Logical supervenience is consistent with non-monism if there is a maximally strong necessitation from the fundamental physical domain to some putative non-physical domain. For example, traditional epiphenomenalism can be made consistent with logical supervenience if the modal relation between the physical base and the supervenient mental state is âbumped upâ from the standard relation of causation to one of maximally strong necessitation. We might call this bizarre theory âlogical epiphenomenalismâ. On the face of it, a brute relation of maximally strong necessity between distinct domains seems extremely implausible. In fact, one might think that such distinctness is marked out precisely by possible modal variation.
The ontological constraint arises from respect for the picture of the world provided by fundamental physics. It appears that the world is, in some significant sense, made out of very small things. At least, the physical objects of familiar experience have parts which have parts ⌠which have parts that eventually connect with the kinds of things described by fundamental physics. It is important to emphasize that âsmallâ does not necessarily mean âparticleâ. The relation between what our fundamental physics tells us about the world â that it is composed of a myriad of quantum fields â and a notion that the world is made up of very small pieces of matter is very far from straightforward. As David Wallace has written: âthe popular impression of particle physics as about the behaviour of lots of little point particles whizzing about bears about as much relation to real particle physics as the earth/air/fire/water theory of matter bears to the Periodic Tableâ (2013, p. 222; see also Fraser 2008 for a technical argument that particles cannot be considered as fundamental in quantum field theory). Presumably, then, the dependence relation we seek is some kind of complex relation of constitution.
It is the job of science broadly construed to work out the details of this constitution relation (or, more likely, the many constitution relations which will be involved in the long, ladder-like transition from the fundamental to the familiar), bearing in mind that the complexity of constituted entities will not permit anything like a full and completely transparent account. For example, we have a pretty good idea of how chemical kinds are constituted based on the principles of quantum mechanics, even though exact calculations from first principles remain outside of our reach for all save the very simplest cases.2 Philosophically however, we need only be concerned with the basic form of the constitution relation, which I suggest is something like the following (restricted for simplicity of presentation to a single property, F), where C stands for a relation of constitution by which a is constituted by the zi which stand in a relation Î which âgeneratesâ the property F:
What this formula says is that if an object, a, has a property, F, then there is a relation which holds amongst its constituents (whatever they may be) such that any such system of constituents related by that relation will necessarily have the property, F.
It is important to bear in mind that a liberal interpretation of this formula is appropriate. There is no commitment to locality in the constitution relation (quantum mechanics suggests that the properties of things are not always determined fully locally), and similarly there is no implication that the correct constitution relation will support anything like partâwhole reductionism (though it is compatible with it).
Obviously, [E] represents a form of emergence3 inasmuch as an object comes to possess a property which its constituents lack. Physicalism will have to embrace some form of emergence.
There are various kinds of emergence but a broad division will suffice for our purposes. Conservative emergence, of which [E] is a partial characterization, essentially claims that emergent properties are simply new ways to describe complex situations. Such new descriptions cannot be directly predicted from underlying theory. Nothing in atmospheric dynamics, for example, predicts the concept âthunderstormâ. But if one was given a new descriptive concept (âthunderstormâ) and a simulation of the world based solely on fundamental laws (a simulation of the atmosphere on a hot, dry afternoon in Alberta say), one would see that complexes in the simulation deserved to be described by the new concept (things acting just like thunderstorms would appear spontaneously in the simulation). Radical emergence goes further, asserting that the emergent properties make a real difference to the workings of the world. Radical emergentism claims that the simulation based only on fundamental physical law would simply fail to simulate the world accurately. If thunderstorms were radically emergent, the atmospheric simulation, no matter how perfect, would go on and on, but never generate anything like a thunderstorm.4
As noted, the properties deployed in fundamental physics are but a tiny fraction of the properties the world exemplifies. But there need be nothing mysterious, mystical or transcendent about the conservative emergence vouchsafed by [E]. No physicalist should be worried about this kind of emergence and in fact they should welcome its inclusion in the physicalist world view.
The strength of the necessity operator, âĄl, is crucial here. It must possess the maximal modal strength of logical necessity (hence the mnemonic subscript âlâ) on pain of the intrusion of phenomena that are not suitably dependent on...
