Mind, Matter, and Nature

4. Materialism

88 Chapter 4 Materialism In the previous chapter we discussed a two-phased materialist strategy for defeating dualism. In the first phase, the materialist argues that dualism is false (or at least beyond reasonable belief). In the second phase, the materialist either argues that there are no such things as psychological states or constructs an account for our psychological states that does not take sensations and thoughts as nonphysical entities. We found that the first phase is not complete in any strong sense; that is, we don’t have good reason to conclude that dualism is beyond the pale. We did find, however, that the dualist (especially the substance dualist) does need to complicate matters greatly in order to reply to these arguments , so a weakened first phase of the materialist project can be defended; that is, we should accept dualism only in the absence of any better account of sensations and thoughts. The materialist can show that there is just such an account by successfully executing the second phase of his project, which is to defend an entirely materialist understanding of our psychological states (or to show that it is plausible to suppose that there are no such things 89 Materialism as psychological states). We will spend this chapter discussing the prospects of this second phase of the materialist’s strategy. Eliminative Materialism Among the various forms of materialism, the easiest version to understand is eliminative materialism. To say that we eliminate x in favor of y is to claim that x and y are not identical and we now have replaced x with y, in the sense that we no longer believe there is any such thing as x and instead believe in the existence of y. For example, in early modern theories of combustion, phlogiston was posited to account for the loss of mass in burned materials . The idea was that some material, phlogiston, must be emitted by the burning substance. Since phlogiston seemed to explain combustion (along with other phenomena including the rusting of metals), scientists believed there was such a material, even though it was not thought to be directly observable. The phlogiston theory was later found to have internal problems, and it was disconfirmed experimentally. A replacement theory, positing oxygen as something consumed during combustion, made better predictions and was free of internal difficulties, while accounting for the same phenomena. Thus, there is no longer reason to believe in phlogiston, but we do accept the existence of oxygen. In short, phlogiston has been eliminated in favor of oxygen in our theory of combustion. Note that in a case of elimination, we don’t claim to find out that the object eliminated is identical to or turns out to be the same thing as the replacement theoretical entity. Scientists do not accept the following proposition: (1) Phlogiston is oxygen. We have discovered not that phlogiston is oxygen, but that there is no such thing as phlogiston! Rather we now know that something entirely different accounts for combustion, namely oxygen. Theoretical eliminations do not result in true identity propositions, but the replacement of a false set of propositions (those postulat- 90 Materialism ing entities of the now obsolete theory) with what we now take to be a true set of propositions (those postulating the entities of the new theory). Since there is no such thing as phlogiston, most propositions that refer to it are strictly false. For example, (2) The burning grass emitted phlogiston is straightforwardly false, because there is no such thing as phlogiston . If you persist in a phlogiston theory of combustion, you maintain a set of false beliefs. Some materialists propose an eliminativist account of psychological entities that literally denies the existence of sensations and thoughts just as we now deny the existence of phlogiston. Paul Churchland, who is the foremost defender of eliminative materialism , defines his position as follows: “Eliminative materialism is the thesis that our commonsense conception of psychological phenomena constitutes a radically false theory, a theory so fundamentally defective that both the principles and ontology of that theory will eventually be displaced ... by a completed neuroscience .”1 According to Churchland and other eliminativists, sensations and thoughts are the entities of a primitive theory (so-called folk psychology) we all employ to explain each other’s outward behavior. We see and hear certain activities on the part of other organisms, and we then posit unseen, inner episodes, that is...