HOW CAN BRAINS PRODUCE CONSCIOUS EXPERIENCES?
In recent years it has become apparent that "the mind/body problem" is not one problem but many, and that some of these problems have become amenable to scientific research (see readings in Velmans, 1996a for a review). However, some of the ancient puzzles persist. Those discussed in Solms's thoughtful paper (this volume) are amongst the most perplexing. What is consciousness? How does human consciousness fit into the complex dynamic of unconscious mental life? How could brain states produce subjective conscious experiences? And how could conscious experiences influence the activity of brains?
These problems interconnect. If conscious experiences are nothing more than brain states (as claimed by the "physicalists" within philosophy of mind) then their causal interaction with brain states presents no philosophical puzzle. It is hardly surprising that this position is popular amongst neuroscientists as this leaves the future to them. It is equally tempting to those psychologists who view their discipline as nothing more than an extension of biological science.
However, the popularity (or theoretical convenience) of a view, has never been a substitute for it being well grounded in evidence or argument. Science has not made some "breakthrough discovery" that our multifaceted conscious lives are nothing more than states of the brain, and there are reasons to believe that it never will (which we examine below). Given this, and given the many apparent differences between conscious experiences and brain states it is odd that their identity is so often taken for granted (as in Crick, 1994, and Searle, 1994). In the brief space available for this commentary I cannot do justice to the reductionist debate within science and philosophy of mind. But let us devote a few lines to why the reduction of consciousness to brain may prove impossible to achieve.
We all have conscious experiences. From our own first-person point of view, experiences are data (which we would like to understand more deeply). They are not "hypothetical constructs" which science might discover to be physically "real" (in the way that genes were found to be DNA molecules). Nor are conscious experiences "prescientific theories" (folk psychologies) to be replaced by a more advanced physical theory of mind. That is, the claim that conscious experiences are nothing more than brain states is a claim about one set of phenomena (the experiences) being nothing more than another set of phenomena (brain states, viewed from the perspective of an external observer).
Given the extensive, apparent differences between conscious experiences and brain states this is a tall order. Formally, one must establish that despite appearances, conscious experiences are ontologically identical to brain states. Instances where phenomena viewed from one perspective turned out to be one and the same as seemingly different phenomena viewed from another perspective do occur in the history of science. A classical example is the way the "morning star" and the "evening star" turned out to be identical (they were both found to be the planet Venus).
But viewing consciousness from a first- versus a third-person perspective is very different to seeing the same planet in the morning or the evening. From a third-person (external observer's) perspective one has no direct access to a subject's conscious experience. Consequently, one has no third-person data (about the experience itself) which can be compared to or contrasted with the subject's first-person data. Neurophysiological investigations are limited, in principle, to isolating the neural correlates or antecedent causes of given experiences. This would be a major scientific advance. However, correlation and causation do not establish ontological identity. These relationships have been persistently confounded in reductionist arguments, so let me make the differences clear.
Ontological identity is symmetrical; that is, if A is identical to B, then B is identical to A. Ontological identity also obeys Leibniz's Law; if A is identical to B, all the properties of A are also properties of B, and vice-versa (for example all the properties of the "morning star" are also properties of the "evening star").
Correlation is also symmetrical; if A correlates with B, then B correlates with A. But correlation does not obey Leibniz's Law; if A correlates with B, it does not follow that all the properties of A and B are the same. For example, height in humans correlates with weight, but height and weight do not have the same set of properties.
Causation, by contrast, is asymmetrical; if A causes B, it does not follow that B causes A. If a rock thrown in a pond causes ripples in the water, it does not follow that ripples in the water cause the rock to be thrown in the pond. And causation does not obey Leibniz's Law (flying rocks and pond ripples have very different properties).
It should be clear from this that it is false to argue (as Crick 1994 and many other have) that isolation of the neural causes and correlates of consciousness will establish consciousness to be nothing more than the activity of neurons. As it happens, many nonreductionist theories of mind agree that consciousness (in humans) is causally influenced by and correlates with neural events; but they deny that consciousness is nothing more than a state of the brain. As no information about consciousness other than its neural causes and correlates is available to neurophysiological investigation of the brain, it is difficult to see how such research could ever settle the issue. The only evidence about what conscious experiences are like comes from first-person sources, which consistently suggest consciousness to be something other or additional to neuronal activity. Given this, I conclude that reductionism (of conscious to brain) cannot be made to work (cf Velmans, 1997).
Given the shaky intellectual grounds for this form of reductionism, it is hard to avoid the conclusion that its popularity is due to the equally shaky (and largely nonscientific) grounds for its main historical rival, the interactionist-dualism of Plato and Descartes (there is also the whiff of gunpowder left over from the battles of science with the Church). Solms is right to pursue other alternatives. I must confess to not being entirely impartial. In many respects, Solms's suggestions and conclusions (developed within the traditions of psychoanalytic theory) are identical to ones that I have arrived at from the perspective of a phenomenologically-sensitive cognitive science. I have space to go into very little of this in this brief commentary (but see Velmans, 1990, 1991a, 1991b, 1993a, 1993b, 1995, 1996b, 1996c, 1996d, 1997). However some of the similarities (and subtle differences) can be illustrated by focusing on just one, central issue.
How can brains produce experiences?
That brain states have a causal influence on conscious experiences seems undeniable. As Thomas Huxley pointed out in 1898, one has only to stick a pin in oneself to give a sufficient demonstration. How brain states cause conscious experiences seems inexplicable. Neural causes might have neural and other physical effects, but how could something "objective" produce something "subjective"? To make matters worse, there appear to four distinct ways in which conscious experiences and brain states can enter into causal sequences. In science, we take it for granted that earlier brain states can influence later brain states (physical® physical causation); in psychotherapy and in our everyday lives we take it for granted that early experiences can influence later experiences (mental® mental causation); along with Huxley, psychiatry takes physical® mental causation for granted (for example, that conscious experience can be altered through the use of drugs); and psychosomatic medicine assumes that mental® physical causation can also take place. Given the extensive evidence for all these causal interactions (Velmans 1996b), how are we to make sense of them?
In order to resolve this puzzle we first have to go back a step. In science, we take physical® physical causation for granted, but worry about any causal sequences which involves (conscious) mental events. But why? Presumably, because we are confident about the ontological nature of the "objective" physical world, and dubious about the "subjective" ontological nature of conscious experiences. However, as Solms notes (following Kant and Freud), observed phenomena are not things-in-themselves. They may represent some underlying reality but they are not themselves that reality in any absolute, "objective" sense. This applies as much to (third-person) observations of brains as it applies to (first-person) observations of our own experiences. While one may or may not be "objective" in one's scientific investigations in the sense of being dispassionate, there are no "objective observations" (of brains or anything else) in the sense of being "observer-free." As Solms points out, this begins to undermine the materialist assumption that third-person access to someone else's mind (via observations of their brain) has some "objective" epistemic priority over the subject's own experiences of their mental states. Conveniently, one does not need to assume third-person observations to be "objective" for investigations of consciousness to proceed. Differences between first- and third-person accounts can be understood to arise from two fundamentally different forms of access to the events described. That is,
"Events viewed from an external observer's perspective (via exteroceptors) appear different from the same events experienced by the subject (via interoceptors) because the methods of observation are different. However, each perspective is legitimate.
Information processing models and other third-person perspective models are incomplete in so far as they do not encompass the subject's first-person perspective. Conversely, a subject's first person account of his actions (based on what he experiences) is incomplete in so far as it does not encompass information available to an external observer. In this sense, first-person and third person perspectives are complementary and mutually irreducible. A complete psychology requires both" (Velmans, 1991a, p667).
"Once one accepts that there are two fundamental forms of access to mental life (first- and third-person) the paradoxical nature of consciousness/brain interaction can, to some extent, be understood (cf Velmans, 1991b, p716; 1993a, p414). While for any individual there is just one mental life (ontological monism), accounts of what appears in consciousness, or of information/brain processing, view that mental life from two fundamentally different perspectives (epistemological dualism). Such accounts can be first-person, third-person, or both. Accounts which are purely first-person or purely third-person do not speak of consciousness/brain causal interactions ....
Accounts which do speak of consciousness/brain interaction are really mixed-perspective explanations, which employ perspectival switching. In psychophysics, for example, causal explanations typically start with stimuli (in the world or the brain) observed from a third-person perspective by the experimenter, and switch to resulting experiences, reported from the first-person perspective of the subject. Accounts of the effects of conscious experiences on subsequent brain or body states typically start with the first-person experiences of the subject and then switch to the resulting brain or body changes (observed by the experimenter) .... Mixed-perspective explanations can, in principle, be unscrambled so that they become pure first- or third-person accounts; for example, in some future neurophysiology one might be able to replace a report of what is experienced with an account of the neural correlates of what is experienced in psychophysics experiments. However, there might be no point to such a third-person reduction. If the aim of the experiment is to chart the way in which physical changes are translated into perceived events, the mixed-perspective account remains the relevant one. That is to say, a mixed-perspective causal explanation may be entirely appropriate depending on the uses to which it is put." (Velmans, 1996d, p541).
Of course, one can still ask
"What is it that appears as neurally encoded information to an external observer, but as a conscious experience from a first-person point of view?" For Spinoza, these may be dual aspects of some deeper "nature", for Kant some "noumenon" or "thing-itself", and for Jung some deeper "self". Looked at in this way, first-person and third-person causal accounts may be thought of as alternative representations of a causal process within the "thing itself." (Velmans 1993a, p414)
It is intriguing to study the way that Solms arrives at the same position via a different route - and a surprise to learn that similar thoughts occurred to Freud!
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--------(1996c) What and where are conscious experiences? In M. Velmans (ed) The Science of Consciousness: Psychological, Neuropsychological and Clinical Reviews Routledge.
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--------(1997) Goodbye to reductionism. In S.Hameroff, A.Kaszniak & A.Scott (eds) Towards a Science of Consciousness: The Second Tucson Discussions and Debates. MIT Press (in press).
Dr Max Velmans
Department of Psychology
Goldsmiths, University of London
London SE14 6NW.