The real psychological phenomena that most seriously might support dualism concern conscious
experience. Your consciousness includes perceptual experiences such as colors, shapes, sounds,
tastes, smells, and touches. You are also often aware of emotional states (e.g., being happy or sad),
bodily feelings (pain, fullness after a meal), and thoughts (I am now reading this chapter). One of the
biggest remaining challenges for neuropsychology is to come up with a plausible explanation of how
such experiences arise from brain processes. Some materialist philosophers and behaviorist
scientists have attempted to stave off the challenge of consciousness by denying its existence, but for
most people the conscious aspect of perceiving, feeling, and thinking is undeniable. To ignore
consciousness would amount to admitting that it provides insurmountable evidence supporting the
soul hypothesis over mind-brain identity.
My strategy for dealing with the problem of explaining consciousness is first to refute arguments
that it cannot possibly be dealt with scientifically, a task pursued in the next section. The more
positive task of sketching what a neuropsychological explanation of consciousness might look like is
pursued in Chapter 5, on how brains feel. There I offer not a general theory of consciousness but
rather a neural model of one important kind of experience, emotional feeling. This model is still
highly provisional but at least suggests one plausible route that neuroscience can take to bring
conscious experience within the scope of causal explanation. The difficulty of accounting for
consciousness is the major obstacle to my more general claim that mind-brain identity is part of the
best explanation of all the available evidence about mental phenomena, but I will try to show how
progress in overcoming it can be made. Other mental phenomena that are sometimes taken to show the
limitations of neural explanations will also be discussed in later chapters, including intuition
(Chapters 5 and 9) and free will (Chapter 6).
If consciousness can be explained by psychology and neuroscience, then the case for mind-brain
identity is overwhelming. I argued that we already have excellent starts on neural explanations for
perception, learning, memory, and other mental processes, such as reading. The main phenomena that
might support the alternative hypothesis that minds are souls, including reports of communication with
the dead, near-death experiences, and parapsychology, can be explained away as incidents of fraud
and error. Consciousness cannot be explained away, but Chapter 5 will point to paths that take it
seriously but suggest how scientific advances might occur.
If minds are brains, we just do not need the hypothesis that they are souls too. Dualist explanations
are inherently less simple than materialist ones, as they posit the existence of two kinds of things
rather than one. Simplicity is not a virtue all by itself, as we see in the hypothesis of the first great
philosopher-scientist, Thales, that everything is water. Einstein said that everything should be as
simple as possible but not simpler, and Thales' hypothesis is just too simple, as was Aristotle's
somewhat more complicated story that the four fundamental elements include earth, air, and fire as
well as water. Modern chemistry sees the need to consider more than a hundred elements, including
hydrogen and oxygen, which combine to produce water. Similarly, it is possible that there could be
phenomena that require explanations invoking soul or spirit in addition to matter and energy.
However, the rapidly progressing development of neuroscientific explanations of many mental
phenomena suggests that souls are no more part of our best general explanatory account than is
caloric, which was thought to be the substance of heat before the advent of the theory that heat is just
molecular motion.
Sufficient evidence has been presented in this chapter to justify using mind-brain identity as the
basis for the rest of the book's discussion of the nature of knowledge, reality, morality, and meaning.
Figure 3.3 shows the overall structure of the inference to the best explanation that minds are brains,
including the kinds of evidence that are increasingly being accounted for in terms of neural
mechanisms. The hypothesis that minds are brains competes with the hypothesis that minds are souls,
whose explanatory successes are few. The figure also shows competition between the higher-level
hypothesis that minds evolved naturally and the hypothesis that minds arise from divine creation. If
you are convinced by my argument that minds are brains, then proceed to Chapter 4. For the sake,
however, of philosophical skeptics about mind-brain identity, I will close this chapter with a
discussion of some of the most influential objections to it.