A simple insight serves to clear away a common confusion surrounding the mind-body problem. The great success of the physical sciences has led many to assume that the formal descriptions contained in scientific theories also provide a metaphysical guide to the essential character of natural phenomena. The insight is that this leap is unwarranted, and therefore the metaphysical thesis of scientific materialism (or physicalism) is founded on a flawed conception of the natural world. To the extent dualists share this conception of the “body” side of the problem, they share the mistake as well. [UPDATE 6 June 2012: light editing]
It’s important to stress that this is not a critique of science. It is a critique of a metaphysical position inspired by science. All science begins with the observations of researchers, but the power and leverage comes from the fact that theories are formulated and then tested by the community, resulting in the removal of potential subjective biases of individuals, and the establishment of a theory which can be used by anyone to describe and predict phenomena. And of course mathematics has turned out to be extremely well suited to theory construction.
These theories remain formal and abstract, however. They describe structures, relations, and quantities. What’s the problem? It is that the theories do not encompass the intrinsic character of phenomena, but only extrinsic features. Why think the objects or events of the universe have such a thing as “intrinsic character”? First, it's not clear a purely formal/mathematical world is coherent. The structure needs something to "hang on". But the obvious answer (too obvious?) is that our own experience in the world directly acquaints us with intrinsic qualitative content. While it is entirely appropriate to ignore this when doing physics, it cannot be forgotten when doing metaphysics.
Importantly, one doesn’t need to think our conscious experience gives us some special knowledge hidden from science. On the contrary, it seems clear the contents of our consciousness can be fraught with confusions and errors. The argument only needs one to acknowledge that our experience has a qualitative and intrinsic (subjective) character.
So what’s the correct metaphysics? At this point a lot of work remains to be done, but grasping this insight is a crucial first step. What follows are quotes from philosophers, whose formulations can press the point home much better than I have done here. I’ll start with Bertrand Russell, who is prominently associated with the argument and whose name is often attached when related ideas are discussed in contemporary philosophy (e.g. “Russellian theory of mind”, or “Russellian monism”)
"Physics, in itself, is exceedlingly abstract, and reveals only certain mathematical characteristics of the material with which it deals."(Analysis of Matter p.10)
"The events which are not perceived by any person who can communicate with me, supposing they have been rightly inferred, have a causal connection with percepts, and are inferred by means of this connection. Much is known about their structure, but nothing about their quality." (p.388)
“Mathematical physics contains such a superstructure of theory that its basis in observation is obscured.” (Human Knowledge p.41)
“There is here a peculiarity: physics never mentions percepts except when it speaks of empirical verification of laws; but if its laws are not concerned with percepts, how can percepts verify them?” (p.219)
Alfred North Whitehead
"There is an error; but it is merely the accidental error of mistaking the abstract for the concrete. It is an example of what I will call the ‘Fallacy of Misplaced Concreteness’. This fallacy is the occasion of great confusion in philosophy." (Science and the Modern World, p.51)
"The enormous success of the scientific abstractions, yielding on the one hand matter, with its simple location in space and time, on the other hand mind, perceiving, suffering, reasoning, but not interfering, has foisted onto philosophy the task of accepting them as the most concrete rendering of fact.
Thereby, modern philosophy has been ruined. It has oscillated in a complex manner between three extremes. There are the dualists, who accept matter and mind on an equal basis, and the two varieties of monists, those who put mind insider matter, and those who put matter inside mind." (p.55)
"The understanding of the physical world has been expanded enormously with the aid of theories and explanations that use concepts not tied to the specifically human perceptual viewpoint.
Powerful as it has proven to be, this bleached-out physical conception of objectivity encounters difficulties if it is put forward as the method for a complete understanding of reality." (The View from Nowhere, pps.14-15)
"The strategy to which I am most drawn stems from the observation that physical theory only characterizes its basic entities relationally, in terms of their causal and other relations to other entities.
There is only one class of intrinsic, non-relational property with which we have any direct familiarity, and that is the class of phenomenal properties." (The Conscious Mind p.153)
"This pivotal shift from thinking about matter as something qualitative to thinking about it as something quantitative drew a revolutionary line that has sharply differentiated modern from pre-modern thinking. In this book I argue that Descartes’ error, and the error that still haunts us, is that we have come to believe that this revolutionary view of matter is all there is to matter." (A Place for Consciousness, p.8)
"Relations within the most intimate parts of nature also get their expression (and, it is tempting to think, their full expression) in terms of algorithms and mathematical formulae.
Let there be a warning: 'This way lies Pythagoreanism.' We must see that physics has tended to be, in Locke's phrase, a 'partial'consideration' qua the measures of quantities and not let it become a denial and an expungement of the properties for and of which the quantities have a measure." (The Mind in Nature p.74)
“It may be added, with Russell, that although physics appears to tell us a great deal about certain of the general structural or mathematical characteristics of the physical, it fails to give us any real insight into the nature of whatever it is that has these characteristics –
For many take this [the ‘mind-body problem’] to be the problem of how mental phenomena can be physical phenomena given what we already know about the nature of the physical. And this is the great mistake of our time. The truth is that we have no good reason to think that we know anything about the physical that gives us any reason to find any problem in the idea that mental or experiential phenomena are physical phenomena.” (“Realistic Materialist Monism” from Towards a Science of Consciousness III, edited by Hameroff, Kaszniak, and Chalmers, p. 23-4)