Eliminative Materialism best explains the nature of the mind. Eliminative materialism is the thesis that the brain is the ground of the mental and that science will eliminate significant portions of the language about the mind that came before brain science. Dualism and identity theory make explanatory mistakes, and it is because of these failures that highlight a reason to accept eliminative materialist view. Dualists posit entities beyond necessity that are more mysterious than what they are trying to explain. Identity theory keeps the language of the dualists when the language is radically misleading and false. Functionalism is the most defensible alternative to eliminative materialism, but this is only true because Multiple Realiziablility is compatible with a form of physicalism I defend. As long as physicalism is maintained, there is no contradiction between the eliminative position and functionalism.
When the dualists were attempting to explain the cause of human behavior, they posited many unobservable entities. The dualists were correct in noticing that there is a reason beyond what they could see that made the human body act intelligently, but they overpopulated their ontology of the mind. Most important to this is the soul or res cogitans. The soul was like a puppeteer that moved the body somehow. One of the big hurdles of dualism was explaining how two different substances could causally interact. This hurdle meant that not only did the dualists to explain the mind but also a series of very speculative laws.
In Paul Churchland’s Eliminative Materialism, he describes a history of eliminations of dualistic hypotheses. Like caloric fluid, philoston, and vitalism are examples of these eliminations.1 Caloric fluid was a theory that posited an unobservable substance that explains heat (TPOM 131). Mean kinetic energy replaced this (TPOM 131).
Philgiston was a spirit-like substance which left rusting or burning objects (TPOM 131). Because philogiston was radically misdescriptive for what was actually occurring (i.e. combustion and oxidation), it was “not suitable for reduction to or identification with some notion from within the new oxygen chemistry, and it was eliminated from science” (TPOM 131).
Vitalism tried to explain why some matter was living and why some was not. It was believed that an animating spirit must explain the different sense at the time people did not know that physical processes could exhaustively explain life. In the case of vitalism, this conceptualization of life was so ingrained in people that it seemed to be a contradiction of terms.
The mind is similar to these, vitalism in particular, in that the properties attributed to it are in conflict with the observable (i.e. the physical). One of the reasons people reject physicalism about the mind is because the mind is said to have freewill but purely physical systems are deterministic. Another is that “it would make sense to say of a molecular movement in the brain that it is swift or slow, straight or circular, but it makes no sense to say this of the experience of seeing something yellow” (TPOM 91). At every turn it seems that the language we inherited for the mind fails to meet what we observe in the brain.
In Churchland’s explanatory argument, he demonstrates why this language ought to be eliminated. Folk psychology has “widespread explanatory, predictive, and manipulative failures” (TPOM 132). Since there has been insignificant progress in folk psycology in the last two thousand years, it makes sense that there would be significant explanatory errors given our scientific progress (TPOM 132). Just like the early Christians thought epilepsy was demon possession and the Greeks thought lunatics were influenced by the moon, our inherited language radically mischaracterizes intelligence, memory, sleep, and mental illness (TPOM 132). Some of these concepts, sleep in particular, will not be eliminated; however, the point here is that methodologically speaking, we should not start with our inherited language to figure out what the mind is but rather the brain. This will definitely help when exploring the causes and possible cures of mental illness which clearly has a physical basis in the brain.
Aside from the cultural and historical reasons for belief in substance dualism, people often appeal to the first-hand knowledge of the mind which gives them insight to its non-physical nature. Richard Rorty counters this with his witch doctor analogy in Mind-Body, Privacy, and Categories. In it, he characterizes a subclass of people called witch doctors who take a special drug (TPOM 114). When someone sick comes to these witch doctors, the drug enables them to see demons which correspond to his or her affliction and prescribe herbal remedies that the demons seem to hate (TPOM 114-5). From the scientifically informed, demon-talk is nonsense. It is germs that cause diseases and appeals to the supernatural only serve to add more mystery to the nature of illness (TPOM 115). Though Rorty appeals to the historical successes of using Occam’s Razor, the reason here is more a priori (TPOM 115). A more complicated theory is less likely to be true than a simpler theory when they both explain the same evidence sufficiently.
With these reasons to reject dualism in favor of eliminative materialism in mind, the identity theory makes the mistake of maintaining the flawed language of the dualists. While correct in identifying the brain as the seat of the mind, their hope that there will be identities for desires, beliefs, and sensations is misguided. Paul Churchland’s inductive argument demonstrates this. He argues from history that folk psychology belongs to a long list of failed hypotheses which will be eliminated (TPOM 133). The reason for this grouping has to do with the methods and general traits that ontologies have been eliminated before in science. Given a history of eliminations, we can reasonably conclude that remaining concepts that carry the same relevant explanatory traits as those already eliminated (i.e. dualistic, unobservable, and mysterious) will also be eliminated as the new science arrives. This means we should avoid grounding any theory of mind in this old language that definitely carries vague and inaccurate terminology (i.e. mental illness and intelligence).
Another argument against the identity theorists is that they make a methodological mistake. As Rorty argues, the identity theorist confuses a translation identity with a disappearance one. On one hand, there is translation identity which is when ‘X is nothing but Y’ (TPOM 113). For instance, chairs are nothing but atoms. On the other, there is disappearance identity which is also ‘X is nothing but Y’ but by the way ‘X does not exist’ (TPOM 113). For example, unicorn horns are nothing but narwhal horns, but by the way unicorns do not exist (TPOM 116). Rorty’s point is that the identity theorist commits to there being desires, sensations, and various other mental phenomena when they should be wary of such ontological commitments. For Rorty, committing to the existence of sensations is like saying that narwhals have unicorn horns, which implies that unicorns exist (TPOM 116). Given Churchland’s argument about the fatal weaknesses of folk psychology, we ought to take the disappearance route when it comes to the mind.
The last alternate theory to consider is functionalism. As already argued, any theory of mind that refers to folk psychology and attempts to draw identities with it is going to fail. This applies to functionalism as well; however, not every functionalism needs to appeal to folk psychology. While identity theory would just be eliminative materialism without folk psychology, functionalism is based on a different assumption and does not necessarily need to make identities between traditional mental ontology and functions. This more eliminativist form of functionalism is what I will address as the greatest competitor for eliminative materialism.
At the core of functionalism are two intuitions which are demonstrated by the multiple realiziability argument (MRA). These two intuitions are 1) properties can be realized by multiple non-identical structures and 2) if a property is held by multiple non-identical structures it cannot be identical with that structure (PM 121). The first intuition seems to imply the second, but there are reasons for rejecting this, which I will not address here.
MRA utilizes the transitive property in order to demonstrate the absurdity of the identity thesis and undermine the unity of science by disassociating properties. The argument can be stated as follows:
- Identity thesis is only true if and only if every mental state is identical with a physical state (PM 97).
- Two beings, A and B, have different kinds of brains such that P1≠def P2.
- When A is in mental state M, A is in brain state P1.
- When B is in mental state M, B is in brain state P2.
- If P1≠def M is true, P2≠def M is also true and vice versa.
- If (P1=def M) and (P2=def M), P1=def P2.
- From 2, 5, and 6, (P1≠def M) and (P2≠def M).
- From 1 and 7, it follows that identity theory is false.
One way the eliminative materialism may respond is to reject the folk psychological baggage that allows for disassociation of mind and body that makes positing the same mental event in non-identical brains possible. The functionalist has a reasonable response that we would be foolish if we thought that only one brain could achieve this property. This response is backed up by a whole realm of properties like color and shape that obviously have non-identical physical realizers. I agree with the functionalist in that eliminative materialist must account for the high probability that similar mental events could be multiply realized.
The only justifiable position in my opinion that the eliminative materialist can take in response to MRA is to embrace the difference between higher and lower properties without committing to a formal property dualism. A formal property dualism would imply that one property supervenes on the other. Since higher properties are derivative of the contextual existence of physical substance that is the basis of all that exists, there relation is importantly different than what supervenience implies. Jaegwon Kim in Philosophy of Mind describes other supervience relations to demonstrate this non-causal aspect the relation by comparing it to the relation some philosophers posit as lying between the physical and the ethical (PM 9). Since the intuition is that ethical properties are not ‘nothing but the physical’, supervience serves to divide two sets of properties as distinct and unbridgeable. This is a rejection of the unity of science.
Rejecting this distinction, Rather than the mental state of A and B being strictly identical with the physical story of their respective brain states, the mental is identical with only a particular part of the physical story while remaining completely a result of each physical story respectively. In other words, the fact that two physical things have the same function (i.e. mental state) does not undermine the physical story behind it. For example, I can cross the sea by plane or by boat. Both do the same thing but have different physical stories. It would be absurd to say that my crossing the sea was somehow not a physical occurrence just because the mode of transportation is different. Similarly, two non-identical molecules may be hit by white light and reflect the color red, but physicists can give detailed account of why the properties of each the molecules respectively and the properties of light result when the two interact to result in red light.
Since this theory of properties provides a sufficient physical account of why mental properties exist, there is no need to appeal to a more complicated theory which would divide the properties in a formally dualistic fashion. Returning to Rorty’s witch doctor example, when presented with two explanatorily sufficient theories, demon theory and germ theory, germ theory wins because it is far simpler. This theory explains why mental states exist but by using the physical laws that are already in our ontology. Formal property dualism would have it that these properties are unbridgeable, positing new kinds of relations like supervience. Like demons theory, this overly complicates and arguably mystifies the relation between the physical story and the mental. In conclusion, eliminative materialism is the best theory because it does not make the explanatory errors of folk psychology and it most simply while remain sufficient explains the nature of the mind.
1 Churchland uses heavenly spheres as his third example but I chose vitalism instead for two reasons. First, it directly relates to how a drive for translation identity between a dualistic concept and a physical instance hindered progress towards a coherent world view. Second, I will address the ‘observable’ elimination that Churchland is aiming for in his heavenly spheres example in Richard Rorty’s witch doctor thought experiment.