Eliminative materialism

In this WiPhi video we’re going to ask: will neuroscience replace folk psychology? Why should you believe in electrons? No one has ever seen one — not even with an electron microscope. But according to excellent scientific theories, electrons exist. These theories are extremely successful, practically powerful, and accepted by experts in every scientific discipline. We know electrons exist, because they play an essential role in many of our best scientific theories. Such things are called theoretical entities. A theoretical entity is something that we are confident is real, but only because it has to be real in order for a theory we believe in to be true. Well, this might sound like a strange question, but what about beliefs? What evidence do we have that there even are such things as “beliefs”? Why believe in beliefs? Or desires, or hopes, or fears, or any of the other mental states we regularly attribute to others and ourselves? One idea is that beliefs are theoretical entities too. “Folk psychology” refers to our capacity to explain and predict other people’s behavior. Many philosophers think of folk psychology as a kind of “theory” that says things like, “When someone believes there is a tiger in the vicinity, and they fear tigers, they will attempt to flee”. Our understanding of beliefs, fears, and other mental states stems from the role they play in folk psychological explanations of behavior. After all, what is a belief? Well, it’s not easy to give a definition. But we all understand how beliefs function. Consider two people leaving for work. Each has to walk to the bus stop; neither wants to get wet. One brings an umbrella, while the other doesn’t. What explains this difference? Folk psychology suggests several answers. The simplest is: one of them believes it might rain, while the other one doesn’t. This explanation also enables us to make accurate predictions. For example, which one will be surprised if it rains? If it’s a theory, folk psychology is an extremely useful one! We literally couldn’t survive without it. So, if we can be confident that electrons exist because of the success of the theories that posit them, we can be confident that beliefs exist because of t success of the theory that posits them! However, this line of thought leads to a troubling question. Electrons are posited by many of our best scientific theories. But is folk psychology our best theory of human behavior? Is it even a good one? A theory’s practical utility is not the only thing that matters. Why does the sun set? Here’s one theory: the sun is a cowardly god who is frightened by humans, and spends every day traveling across the sky trying to escape our gaze. This theory predicts with perfect accuracy that the sun will set tomorrow. However, we have no reason to believe that it’s true. We have a much better theory to explain the sunset — namely, that the earth rotates on its axis every 24 hours, and hence the sun disappears from view from each part of the planet once every 24 hours. What if there were a theory of human behavior that didn’t involve beliefs, desires, and so on? And what if this theory were even better than folk psychology? Good as it is, folk psychology is hardly fool-proof! We’re often wrong about why someone did what they did, or what they will do next. Some philosophers think that neuroscience will eventually give us a much better theory of human behavior than folk psychology. But if that happens, would we still have any basis for thinking there are such things as beliefs, desires, and the other mental states posited by folk psychology? Old biological theories posited the existence of “vital spirits” to explain life. Contemporary biochemistry has no need for vital spirits, as it can explain life processes in terms of general chemical principles. Since it’s a superior theory in many ways, we no longer have any basis for positing the existence of vital spirits. Eliminative materialists think neuroscience will prove superior to folk psychology in just the same way that biochemistry is superior to vitalism. Unlike folk psychology, it’s unified with chemistry, physics, and the rest of modern science; it’s capable of precise experimental testing; it’s developing slowly and methodically on the basis of a foundation of very well confirmed findings, fostered by a global community of experts. And unlike folk psychology, neuroscience doesn’t posit the existence of beliefs, desires, or any other ordinary mental state. It deals in brains, chemistry, physics, and mathematics. If neuroscience gives us a better theory for understanding human behavior than folk psychology does, would we still have any reason to believe in beliefs? What do you think?