A vast amount has been written about the relationship between mind and brain and we cannot review the topic here. But one question is particularly interesting: why, when our understanding of brain function is burgeoning thanks to advances in neurobiology, does so much debate about minds continue? The following statements (and others of similar kind) are affirmed by some writers and denied by others:
These assertions suggest that mind cannot be explained in terms of brain. It is very difficult to free oneself of the intuition of "dualism", i.e. that our "selves", our minds, are distinct from but somehow inhabit our bodies.
Some interesting experiments conducted during the 1970s and 1980s demonstrate that when we form an intention to do something, e.g. to perform a simple act such as bending a finger, changes take place in the brain hundreds of milliseconds before we make the "conscious intent". In other words, the relevant events in the brain precede the mental event - the "act of will". Thus, minds are in a real (though still obscure) sense caused by brains.
There is plenty of evidence to support this claim. Sensations such as pain in a specific part of the body can be evoked merely by stimulating the right neurones in the cerebral cortex. Specific memories can be evoked in a similar way. Every mental event is not merely accompanied by a particular brain event, often involving a great many neurones, it is immediately preceded by the brain event.
However, there are good reasons for rejecting the extreme reductionist view that "mind" is not worth considering, that we should focus attention exclusively on studying the brain instead. For one thing, the advice is impossible to follow. Much of our everyday language and thought presupposes the existence of mind. To replace attitudinal terms such as "desire", "appreciate", "believe" and "dislike" with descriptions of the relevant brain events would be absurd, even if it were possible in practice. Also, to deny the existence of mind is self-contradictory; it is tantamount to declaring "I do not exist". To say that "mind" is not a useful concept is rather like saying that "life" is not a useful concept. In the first half of this book we argued that life is matter organised in an autonomous, high-order way: a self-sustaining reciprocal dependence among gene expression pattern, responses to external stimuli and internal state. Analogously, we might say that mind is brain function organised in a self-sustaining high-order way. Roughly speaking, mind is to brain as life is to cell. We shall explore this analogy in chapter 18.
A brain capable of intelligent behaviour continually correlates information from the rest of the body with information from the perceived environment. There is fine division of labour, but higher-order brain processes integrate the parts, creating (for instance) connected experiences by combining impressions of form, colour and movement (derived from vision) with information from other senses such as sound, and with appropriate emotions and actions. The brain must also ensure that its integrated image of the world, and the behaviour that it initiates, is consistent from moment to moment. A brain that can do all this is a valuable tool for survival. If the number of synaptic connections between sensory input and behavioural output is sufficiently great, it is also a necessary - and perhaps sufficient - condition for mind.
However, it is fair to ask whether a human brain, if it could be kept alive in isolation, receiving no sensory inputs and able to generate no behavioural outputs at all, could "cause" (or be directly associated with) a mind. The answer is probably "no", just as an isolated cell would cease to live if it were deprived of all signals from the environment and rendered incapable of specific outputs. Several well-known experiments have shown that sensory deprivation quite rapidly disorientates human subjects; in effect, they begin to lose their minds. Minds are "caused" by brains that are actively processing sensory inputs and generating outputs, not by brains in isolation.
A brain that can abstract as well as order the information it receives from the body, and can express it via (e.g.) language, thereby creates a representation, a subjective mental state. This is what the human brain does. The subjective/objective division between mind and brain might therefore be less problematic than is often claimed. Moreover, abstract association integrates the brain's representations of self and world into a continuous and consistent unitary experience. This unitary experience is our sense of self, i.e. consciousness. So consciousness might not be hopelessly resistant to biological explanation, as (for example) Cairns-Smith and Chalmers maintain - but nor is it a mere "linguistic confusion", as Dennett claims.
In short, the mind-brain relationship might be less problematic than is generally believed, so long as it is viewed from the appropriate perspective: i.e. how the human brain evolved, and what biological purpose it serves. This perspective no more denigrates mind than our characterisation of the living state denigrated life. We believe that "consciousness" is neither a linguistic confusion nor a mystery that cannot be assimilated into conventional biology.
The capacity to abstract and articulate brain processes, enabling us to make long-term predictions, is uniquely developed in modern humans. This capacity, the root of our culture, evolved under very specific circumstances. Ancestral hominids that were already capable of intelligent behaviour produced bipedal and very highly social descendants. The sheer improbability of this combination of circumstances (intelligent behaviour, high social development and bipedalism coinciding in the same species) could explain why "human intelligence" has only evolved once on Earth and is unlikely to be simulated anywhere else in the universe (chapter 15). Other animals that behave intelligently must have higher-order integration of their brain functions, but they lack our capacity for abstract representation. They no doubt have a sense of self and can detect patterns and continuity within themselves and the world around them; but without the ability to abstract or to express these abstractions, they cannot have the kind of mental lives that humans have.
At what stage in human evolution did "mind" appear? Like language, it probably emerged step by step. Evidence of material culture at a particular time in human evolution might indicate the level of "mind" at that time. If so, there is an interesting implication. If our brains are continuing to grow as our culture becomes more complex, then our minds are still evolving. This inference will not appeal to evolutionary psychologists.
In chapter 18 we shall expand these arguments and clarify them.
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