If you tend to be uncontrollable and violent, if you make unnatural sounds and movements, if you are often sick or vomit unusual objects and if your friends tell you that you live a wicked life, it is probably because you are possessed by a demon. Showing your supernatural strength and your friendship with the devil might give it away, too. “You are possessed by Choronzon, the temporary personification of the raving forces of the Abyss” clearly is an explanation for unusual behavior.

Nonetheless I do not believe in demons. The concept of demons is lousy at explaining what goes on in ill minds and has been replaced by psychological theories that, albeit less colorful, have much greater explanatory power. Nothing that exists in the real world has been shown to inhabit the causal position that was attributed to demons with regard to mental “misbehavior”.

Eliminative materialists deny that beliefs are any more real than demons. According to Paul Churchland, beliefs and other propositional attitudes don’t refer to anything in the real world. Nothing has the causal and semantic properties we attribute to beliefs, therefore these concepts will eventually be replaced by a theory of mind that explains our actions, thoughts and sensations a lot better than folk psychology and that is based on empiricism rather than introspection.

In order to examine whether eliminative materialism makes sense, I am first going to look at what folk psychology, the theory eliminative materialism intends to replace, actually looks like and, especially, what the building blocks of folk psychology — propositional attitudes like beliefs and desires — really are. In the next step, I evaluate Churchland’s arguments in favor of eliminative materialism and contrast his theory with an approach to the theory of mind that does not question the validity of propositional attitudes.

Folk Psychology

A proposition is the content of a statement that can be true or false. When we talk about the world, we usually use propositions. “It is raining outside” is a simple example. A propositional attitude is the attitude of a person towards a proposition. I can have different attitudes towards one proposition, for instance, I can believe that it is raining outside, I can desire rain or fear rain. Intentionality is often described as the “aboutness” of mental states. Mental states have the unique property of being directed at objects. Since propositional states, e.g. the hope that it is raining outside, are about something, in my example the rain outside, they are said to be intentional mental states.

When Churchland uses the term “folk psychology”, he refers to our habit of relating different propositional attitudes towards each other in law-like ways. Two propositional attitudes may be equivalent, mutually inconsistent or one attitude may entail the other. When we talk about other people and we mention that someone fears that x happens, we usually infer that this person does not desire that x happens. We are experts at predicting the behavior of other persons by attributing certain attitudes to them and thinking about the actions these attitudes result in.

We are similarly good at predicting the physical behavior of middle-sized, common objects because doing so was just as helpful in our evolutionary past as being able to predict the behavior of our friends and foes. Nonetheless, our common-sense beliefs about physics are as intuitive as they are fundamentally flawed. If you did not take physics in high school, you might even think that there is such as thing as objective time. It turns out that this is not true. For some observers, A happens before B, for others B before A — a fact that is hard to digest even years after hearing about it the first time.

Scientific Thinking

When we ponder how to decide the question whether we have reason to think that our intuitive notion of beliefs and similar attitudes is not as far from reality as our intuitive notion of physics, it is helpful to remember how we decide analogous questions in physics. When we have two competing theories and none of them is obviously false, we let nature decide and favor the theory that is most exact in its predictions. If one theory works well for one area and a different theory works better for others — think of general relativity and quantum mechanics — we choose predictive success over consistency and use each theory where it works best.

Before starting to take apart folk psychology in scientific terms, we first need to establish whether it actually is a scientific theory. In science, a theory is an explanation of a natural phenomenon that is capable of predicting future observations of the same kind, and capable of being falsified through empirical observation. Our network of common-sense psychological concepts enables us to explain and predict the behavior of other persons with remarkable success. Since these predictions are predictions over behavior, they can be falsified, and, if they are falsified, we need to doubt the folk-psychological hypotheses folk-psychology relies on.

According to Churchland, folk psychology is inadequate in its explanations, has not improved significantly over the last 2000 years, limits its explanatory power by focusing on propositional elements and does not even have the normative qualities that are sometimes attributed to it.

It is true that folk psychology cannot explain lots of important phenomena. Mental illness, creativity, differences in intelligence, the psychological function of sleep, perceptual illusions, nonlinguistic learning processes — the list of those aspects of mind that are not accounted for by our everyday thinking in terms of propositional attitudes could be almost arbitrarily long. This does not necessarily imply that folk psychology is false, but it does suggest that, as a scientific theory, it is by far more shallow than an elaborate theory of mind should be. A theory that makes no predictions at all about lots of the phenomena we are interested in is only barely better than a theory that makes wrong predictions.

Folk psychology has remained largely unchanged for the last 2000 years. Looking at the list of unexplained phenomena, one could expect a steady improvement of folk psychology in order for it to catch up with the advances of neuroscience. Nothing like this is happening. For all practical purposes, the folk psychology of today is identical to the folk psychology of the Greeks two or three thousand years ago.

Folk psychology is limited by the fact that its elements are modeled on the elements of human language. This is a subtle point. We live in a world where nearly all the talk about thoughts is talk about propositions, therefore the constraints that are imposed upon us are not apparent to us. Nonetheless they do exist and keep us from describing processes like the large-scale non-linguistic conceptual changes that go on during the first months of a new-born in any meaningful way.

Even as a normative theory, a theory that describes how we should behave, folk psychology is far from perfect. The normative dimension of folk psychology depends on how we value the propositions it deals with, its rationality is not ideal (since we do not know how such a rationality would look like) and it is questionable whether a framework of cognitive virtue would really work on the level of propositional attitudes since this presupposes the use of language.

Eliminative Materialism

The conclusion from all these deficits is called eliminative materialism and can be summed up as follows: Folk psychology describes our internal activities in a way that is a radically inadequate. As a scientific theory, it is probably too confused and too incomplete than that it could ever be fixed by small adjustments and, therefore, it will be replaced by a better theory sooner or later. Even if it is hard to imagine a world that does completely without current folk psychology since this theory is involved with every aspect of our culture, it does not have any features that justify its predominant status.

Quite to the contrary: If we accept that our introspective judgement does not have any special status or any guarantee for being right, we might realize that the conviction that there has to exist something that has the causal and semantic properties we attribute to propositional attitudes has long been one of the obstacles to a unified theory of mind. It might feel as if our thoughts were about something, but this is less important for the issue at hand than one might think. How something feels to us does not say much about how the physical reality of our thought processes looks like. The subjective feeling itself is to be explained by qualia, not by intentionality, and Churchland does not claim that qualia can be eliminated. The concept of intentionality, however, will turn out to be empty quickly as soon as we switch to the framework of eliminative materialism.

The central claim of eliminative materialism might be one of those facts that are hard to digest even years after hearing about them the first time: Beliefs will not be explained by neuroscience as the result of some low-level brain functions. Beliefs simply don’t exist.

Still I won’t be able to stop thinking in terms of beliefs and desires, fears and hopes, mostly because it is the only way that works from a pragmatic point of view. I have to admit that I could not give up my Newtonian intuitions on everyday physics after I learned about general relativity and quantum physics either. The human mind has not been shaped by evolution to match reality where a less expensive and less accurate hack suffices to keep our genes in circulation. The best we can currently hope for is to realize that it is not the world that is bizarre — it is our intuitions.