- René Descartes: Substance Dualism
- On Descartes’ view, can we ever know that other minds exist? Why or why not?
- How does Descartes use the notion of divisibility to argue that the mind exists independently from the body?
- Gilbert Ryle: Exorcising Descartes’ “Ghost in the Machine”
- What is the category mistake that the official doctrine is said to make?
- According to Ryle, what is the origin of the official doctrine’s category mistake?
- J. P. Moreland: A Contemporary Defense of Dualism
- What reasons does Moreland give for rejecting physicalism?
- What reasons does Moreland provide for rejecting epiphenomenalism?
- Paul Churchland: On Functionalism and Materialism
- What are the main arguments against the identity theory?
- What is the “inverted-spectrum thought experiment”? What does it purport to show?
- J. J. C. Smart: Sensations and Brain Processes
- What is Smart’s argument for the identity theory? What is the weakest premise? Why?
- What counterargument can be made against Smart’s position?
- Thomas Nagel: What Is It Like to Be a Bat?
- What point is Nagel trying to make with the bat example?
- How does the nature of subjective experience count against reductive theories of mind?
- Jerry A. Fodor: The Mind-Body Problem
- What reasons does Fodor give for preferring functionalism over competing theories?
- Why does Fodor prefer functionalism over the identity theory?
- David Chalmers: Property Dualism
- How does property dualism differ from traditional substance dualism?
- What is property dualism? Does it reject materialism? Does it posit a ghost in the machine?
- John Searle: Minds, Brains, and Computers
- Why does Searle say that strong AI is false?
- What is the Chinese room thought experiment? What does it purport to show about strong AI?
- Ned Block: Troubles with Functionalism
- What is the Chinese nation argument? Are you persuaded by it? Why or why not?
- What are some of the objections to the Chinese nation scenario that Block considers? Do any of these convince you that the Chinese nation argument is mistaken? Explain.
- John Locke: Our Psychological Properties Define the Self
- What is the point of Locke’s thought experiment about the prince and the cobbler?
- On Locke’s account, how is memory involved in the notion of personal identity?
- David Hume: We Have No Substantial Self with Which We Are Identical
- Do you agree with Hume that “self” is merely a stream of consciousness and not a substance or distinct entity? Explain.
- What is Hume’s argument for the nonexistence of the self?
- Buddhist Scripture: Questions to King Milinda
- Why does Nagasena think that the soul or self is an illusion? Do you agree with him? Why or why not?
- Many Buddhists find the notion of no-soul before and after death comforting. Do you? Why or why not?
Case Two: The Mind-Body Problem
The mind-body problem is the problem of understanding what the relation between the mind and body is, or more precisely, whether mental phenomena are a subset of physical phenomena or not. There are many philosophical positions associated with this problem—substance dualism (“mind and body are two different substances”), property dualism (“there is only one, physical substance, but mental properties of subjects cannot be reduced to their physical properties”), and physicalist reductionism (“mental properties can be identified with, or can be spelled out in terms of, physical properties”), among other positions.
Some philosophers in recent decades have argued that modern neuroscience has already given us an answer to this question: Mental states are nothing other than neural states, and we can talk of mental phenomena through physical vocabulary without any loss of meaning or reference. The founders of what is called “neurophilosophy,” Patricia and Paul Churchland, have been among the most famous advocates of this position, even though their views oscillated between reductionism and eliminativism, the latter view being that mentality (or certain aspects of it) is a prescientific construct that will have no place in the scientific understanding of the world once we have a fully developed neuroscience (see, e.g., Churchland, 1988).
This brand of reductionism relies heavily on the findings of neuroscience, often on quite detailed empirical data about the relation between certain psychological states and brain states or how neural processes generate behavior. Well, almost all brands of reductionism have some reference or other to the brain science, but they are often uninterested in detailed data. Rather, they simply point to the general scientific consensus that there is a very direct relation between mental and neural states, but this relation by itself does not play an important role in their arguments, for these arguments generally rely on a conceptual analysis of mental states to see if mental states could be reduced to any physical states to begin with, and if such reduction is possible, modern day science tells us which physical states are the reduction base, which turns out to be neural or bodily states. On the other hand, the kind of reductionism we are interested in here takes it that science has proven mind-brain identity.
However, the scientific evidence does not settle the philosophical question. No matter what detailed and direct mapping we establish between mental and neural states, there are so many options that remain on the table before we can proclaim that we have reduced mental processes to brain processes. The first obstacle is that correlation does not mean identity, and the reductionist should answer arguments to the effect that the relation is better explained as a correlation. The most important and pervasive argument I will mention here is the argument that, to put it roughly, the reduction of mental phenomena to physical phenomena does not make sense, on conceptual or logical grounds. A phenomenon described by a physical description like “such and such connectivity and firing in this and that brain area” simply cannot be identical to “feeling pain” or “thinking about Budapest” or “having a visual experience of a yellow lemon” as these mental phenomena have certain characteristics that the physical description does not capture, even though antireductionist philosophers disagree on what these characteristics are. Some say it is some subjective aspect, the “feel” or “what-it-is-likeness” associated with the mental state, others say it is “intentionality,” the property of “having a content” or “being directed to an object,” such as the object experienced or thought about. When we are given a description like “such and such neural firing,” we cannot infer whether this state is an experience of the color green or color red or something else. This disparity is termed “the explanatory gap”: A successful reduction, it is argued, should tell us not only an identity based on an observation of a correlation between the occurrence of mental and neural states, but also make us understand how is it possible that such and such mental firing could constitute experiencing the color red (Levine, 2001). Another very different antireductionist argument, a behaviorist one, is the argument that the mind cannot be the brain because mental terms do not strictly refer to states or processes, but dispositions to behave, and it doesn’t make sense to identify a disposition with a state or process (Ryle, 1949).
Of course, philosophers have answers to these challenges. Some claim that identities don’t require an explanation (Block & Stalnaker, 1999), others try to analyze mental phenomena into physical or “topic-neutral” vocabulary (vocabulary that is common both to physical and mental terminology, such as the vocabulary of basic ontological phenomena like causation; the approach was popularized by Smart (1959) and many causal-informational analyses of mental phenomena can be considered as a continuation of this strategy). To give a more specific example, some philosophers like Millikan analyze mental states as natural indicators, e.g., “thinking of X” is being in a state that has the function of indicating the presence of X. So in the case of humans, it is a brain state that has acquired the biological function of signaling the presence of X through the organism’s interaction with its environment (Millikan, 1984). Again, it is not important for us here whether this analysis is correct or not. But if this analysis is correct, then there is no obstacle for mental states to be reduced to neural states—as instances at least, if not as scientific or functional kinds, since different types of neural states can realize the same mental states—and one doesn’t need to look at detailed empirical data to claim that reduction is possible, given that every mental state will correlate with some neural state. From then on, if Millikan’s analysis is accepted, whether mental state M is identical to neural state N is philosophically uninteresting in the context of the mind-body problem, i.e., further empirical evidence does not add anything to the solution of the philosophical problem.