Wednesday, December 5, 2012

Nagel, Reductionism, Materialism, & Physicalism

I am reading Thomas Nagel’s Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False.  It’s pretty intriguing so far.  I hear echoes of Hans Jonas in it, though I haven’t checked the bibliography yet.  I will comment on the work after I have finished reading it. 
For now I want to comment on three very common terms in the philosophy of science, two of which Nagel employs in the first two chapters (reductionism and materialism) and one that he does not (physicalism).  It seems to me that even very basic treatments of these topics frequently fail to adequately define them, let alone get them right. 
Reductionism comes in two very different versions.  Both versions posit distinct levels of interpretation applying to the same phenomenon.  For example, the human body consists of organs that in turn consist of cells that in turn consist of molecules.  Any organic action can be interpreted or modeled at each level.  The beating of the heart can interpreted as the action of a pump.  The contraction of the muscle can be interpreted as the work of set of cells, etc. 
Greedy reductionism involves the view that the higher (which is to say more inclusive) levels are not real.  Only some lower, more fundamental level, perhaps at the molecular or atomic level, is real.  An analogy would be to the people on a TV screen.  The look to be real people but this is an illusion; they are produced by pixels on the flat screen along with the mechanics of the home video box you bought at Target. 
The non-greedy version of reductionism, entirely defensible in my view, is that the higher levels of order are entirely composed of the simpler elements.  My house key, for example, is entirely composed of metal.  The metal has its molecular level at which the laws of chemistry and physics are rigorously enforced.  Nonetheless, the key is real in both an epistemological and a metaphysical sense.  No knowledge of the chemistry of metals would tell you what a key is, nor would the same molecules be physical capable of opening my front door if the key were melted down into a puddle of brass. 
Materialism is a universally abused term.  It is usually taken to mean that everything that is real is composed of matter.  In those terms it is manifestly false, since space and time and energy are all immaterial in nature even if they are measured by a material apparatus.  However, the term materialism ought to confined, in my view, to a certain doctrine about nature and natural change.  A genuinely materialist explanation, such as several Pre-Socratic philosophers attempted, would account for every characteristic of a thing in terms of a specific type of material.  Any change in a thing would be the result in a change in the kinds and amounts of basic matter. 
If a thing is both heavy and shiny, that is because it has particles that present with those characteristics, perhaps earth and fire as the ancients would sometimes have it.  The most famous example of a genuinely materialistic explanatory scheme is the caloric theory of heat.  Something becomes hot when it is saturated with particles of heat, or caloric.  If you rest a hot stone on a table top for a bit and then remove it, a warm impression will be left on the wood.  That is because the heat particles leaked out into the table top.  I submit that only explanations of this kind deserve to be called materialism. 
By contrast, the molecular theory of heat interprets the phenomenon as the level of energy at which the molecules of a substance are moving relative to one another.  That the same set of particles can display different states is thus not a materialist explanation but a formalist one, to coin a term.  There is no doubt but that materialist explanations have a big role in science, as anyone knows who is familiar with the periodic table.  There is no doubt that materialist explanations alone are inadequate to explain all but the simplest phenomena. 
The third term is physicalism.  This is frequently used interchangeably with materialism.  It indicates the view that nothing is real except what is physical.  But what does “physical” mean?  Of the three terms discussed here, this one seems to me to be the most neglected. 
I offer a simple definition: the physical is anything that is in principle measurable.  Thus space, time, and all material objects are physical.  We can pull out the measuring tapes, clocks, thermometers and scales to make a reading.  Even if some characteristic is not practically measureable (say the average temperature on some distant plant’s atmosphere), it counts as physical in so far as we could imagine how to measure it. 
By my interpretation, physicalism has a good claim to comprehend almost all the observable universe, if only because of the fact that we can observe it.  The obvious exception is consciousness.  Modern science has all sorts of ways of measuring things that are related to conscious awareness: brain activity, behavior, etc.  We do not have any way to measure how sincerely Brad loves Janet, nor do we have any idea how we could measure that phenomenon directly.  While we might someday have such an idea, at present consciousness presents as something non-physical. 
That seems to be the point of departure for Nagel’s argument. 

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