The Causal Efficacy of Conscious States
Those who oppose dualists (whom they tend to call empirical idiots or metaphysical windbags) have no patience with what they see as talk of a "ghost" or "hidden controller" or "little man inside the head watching events in the mental theater." Conscious states are not anywhere in space, and so, they say, it should simply be admitted that they are nowhere. In other words, there is none. To talk of conscious states is just to talk of states of the brain, and we know perfectly well where they are—inside the brain.
But sensible dualists, assuming there are some, do not want to speak of ghosts and little men in the brain. They just want to say that there are perceptions, thoughts, and feelings, in addition to electrochemical discharges in the brain. The Cartesian theater is the world itself, as it appears in our phenomenal fields. To whom does it appear? To the more-or-less unitary consciousness that is the functioning complex integrated brain, responding to stimuli from its physical environment. The materialist misrepresentation of the situation is that we think of the mental theater as a very small material object inside the head and the hidden observer as a very tiny body sitting in the theater. But we need to eject all such material elements from our picture. There is no physical theater inside the head. There is the brain, whose activity is registered to itself as a series of conscious events. And there is no tiny body in the head. There is the series of conscious events itself, a series of nonphysical properties of physical events in the prefrontal cortex.
At this point, a gap may seem to open up between what are called "substance dualists" and "property dualists." The property dualist will say that there are two different sorts of properties—physical and consciousness properties. But conscious states, though real, are properties of physical things (embodied brains). They could not exist without the physical things of which they are properties. The substance dualist, however, will say that there are two different sorts of things (substances),—physical things and conscious things (things that have conscious states). In this case, conscious substances (minds) could, in principle, exist without the physical substances with which they are, in human experience, strongly correlated.
I do not think this distinction is as clear-cut as it may seem. It depends upon making a sharp contrast between properties, which cannot exist alone, and substances, which can. However, there are well-known difficulties in saying just what a substance is, over and above the sum of its properties. For Buddhists and for logical positivists alike, a substance is just a collection of properties, and the question of what sets of properties can exist without other sets is largely a matter of contingent fact.
Once existent conscious states have been affirmed, it seems to be a matter of contingent fact whether they could exist without the physical states that are usually correlated with them. Perhaps the distinction between substance and property dualists is largely a verbal one—just another way of asserting, or denying, that some conscious states could exist without any physical states. And that does seem to be a question of fact that verbal definition alone cannot settle.
Both substance and property dualists agree that conscious events exist and are dependent upon the functioning of the brain. But there is something more to be said. In human experience, we do not seem to be just passive recipients of perceptions and thoughts. We seem to see, concentrate, attend, and think in an active way. This implies that conscious events—intentions and decisions—exercise a causal influence on physical events. Can events in consciousness exercise a causal influence upon the physical brain?
Much work in neuropsychology suggests that they can. I am not talking about highly disputed topics, such as telepathy or "psychic connections." I am thinking of the sort of evidence adduced by Malcolm Jeeves in his 2006 paper "Linking Mind and Brain." Research on Braille readers and other blind subjects revealed that habitual behavior has causal effects on the neural substrate of such activity (Sadato et al. 1996). The primary and secondary visual cortical areas of blind subjects were activated when the subjects performed tactile tasks. This is a case where it is not the physical events in the brain that cause experiences and activities, in a sort of one-way causal chain. It is a case where specific activities cause events in the brain that do not exist in normally sighted patients.
A brain-scan study of London taxi drivers (Maguire et al. 2000) revealed that the posterior hippocampi of taxi drivers were significantly larger than those of a non-taxi-driving control group. It seems that behavior and learning can cause local plastic changes in the structure of the adult human brain. That is, intelligent behavior can cause changes in brain structure.
It is not being claimed that there are some mystical or purely psychic causes of physical events. But it does seem that there is not simply a oneway causal path between brain and intelligent activity. Intelligent behavior can cause changes in brain structure and activity.
In the field of psychoneuroimmunology, there are many examples of changes in personal attitudes and in social situation giving rise to changes in cerebral and endocrine processes. The well-established placebo effect, by which a physically neutral drug improves health if the patient thinks it is going to do so, seems to show that beliefs can have physical effects. And it is fairly clear that resolving to adopt positive mental attitudes can have a marked positive influence on physical health. The Handbook of Religion and Health (Koenig et al. 2000) reviews two thousand published experiments designed to test the relation of religious beliefs to conditions such as heart disease, cancer, and depression. Most of these experiments suggest that there is a significant positive correlation between belief and longevity and health.
It may be, of course, that the brain causes both religious belief and good health. But the most natural view is that changes in social circumstances, in intelligent behavior, and in belief can produce effects on brain and body. Experimental work shows that conscious beliefs and practices supervene on behavior and responses to environment that do not need to possess a conscious element. But the available experiments also show that there is what is often called "top-down" causation, by which the brain is affected by a wider system of which it is a part. This includes not only the whole body in which the brain exists but also the field of social relationships and the environment within which bodies exist. Within these wider systems, thoughts, feelings, and intelligently directed behavior are not simply the effects of physical brain processes, working in a "bottom-up" way. They are conscious responses to the environment, and they can influence, to some degree, physical states of brain and body.
Nobel laureate Roger Sperry writes, "A mutual interaction between the neural and mental events is recognized: the brain physiology determines the mental effects, as generally agreed, but also the neuro-physiology, at the same time, is reciprocally governed by the higher subjective properties of the enveloping mental events" (cited in Gregory 1987, 164—65). For Sperry, consciousness is an irreducible working component in brain function—"the colorful and value rich world of inner experience, long excluded from the domain of science by behaviorist materialist doctrine, has been reinstated."
This whole area is highly controversial, and it is probably true to say that many neuroscientists tend toward a strictly materialist view, that minds are no more than brains. They would usually admit, however, that the "problem of consciousness" remains wholly unsolved, and it is not even very clear just what a solution would be, in purely physical terms. Very few have the confidence of Daniel Dennett, and that confidence has more the character of faith—commitment to a theory without overwhelming evidence because it seems to have practical benefits—than of verified theory.