杏吧原创

Can science explain the self, or is that just neuro-scientific hubris? There鈥檚 no need to take sides

THE nature of the self, identity, and human values used to be the preserve of philosophers, but over recent decades psychologists and neuroscientists seem to have thoroughly colonised the territory.

For instance, in the 1960s Roger Sperry and Michael Gazzaniga famously severed the corpus callosum in several people with epilepsy and found that the left hemisphere of the brain could be aware of things the right was not aware of, and vice versa. Then in the 1970s, Benjamin Libet discovered that certain bodily movements were activated in the brain before the person consciously decided to do them, challenging conventional notions of free will.

A decade on, and Michael Persinger brought religious experiences into the domain of neuroscience by inducing them in subjects using transcranial magnetic stimulation. Moving into the 21st century, and neuroscientists such as Todd E. Feinberg and Antonio Damasio continue to use research into the brain to shed light on how our sense of self is created and sustained.

In contrast, my book on self and identity, The Ego Trick, contains just one chapter on the science of the brain. Why? Because I would argue that on the big questions about who we are, recent research has told us a great deal about the physical basis for the emergence of the sense of self, but next to nothing about what a self actually is.

Take the question of what the seat of the self is. For millennia, in the absence of any real understanding of consciousness, it seemed credible to believe that thought required some kind of immaterial soul. The big contribution of empirical science has been to identify the brain, working with the central nervous system and to some extent the whole body, as the main organ responsible for consciousness.

But this very general idea is hardly cutting edge. As long ago as 1664, Thomas Willis published Cerebri Anatome, a detailed attempt to explain how different parts of the brain produced the different 鈥渁nimal spirits鈥� that were believed to power thought and action. More importantly, even before the brain鈥檚 role in consciousness was fully appreciated, philosophers such as the British empiricists John Locke and David Hume had already worked out that what you are isn鈥檛 a question of the stuff you are made out of anyway, be it spirit or matter. What makes you the same person over time is, broadly, the continuity of your mental life. The continuity of the same brain in the same body matters only in so far as it makes this possible. As cognitive scientist Douglas Hofstadter memorably put it, 鈥渋t ain鈥檛 the meat, it鈥檚 the motion鈥�. We knew this before neuroscience peered into the brain and discovered what makes that motion happen.

But what about the much finer-grained work of recent years, pinpointing exactly which parts of the brain are responsible for the various aspects of consciousness? This is clearly extremely interesting and clinically useful, but philosophically speaking it really only filled in the details and hammered the last nails into the coffins of antiquated views of soul and self. Neuroscientists, for example, agree there is no place in the brain where 鈥渋t all comes together鈥�, no locus of the self in one part of the cerebrum. A sense of self turns out to be something that emerges as the result of most parts of the brain working together.

Using Feinberg鈥檚 model, the self is a 鈥渘ested hierarchy鈥�. This means that the higher functions of self 鈥� self-consciousness, for example 鈥� are not independent of the lower functions, like the basic awareness of one鈥檚 environment, but incorporate and depend on them. So the higher functions of the evolutionarily newest part of the brain, the cerebral cortex, require the more primitive instinctive and emotional functions of the limbic system (amygdala, hippocampus and hypothalamus) and the automatic bodily regulation functions of our 鈥渞eptilian brains鈥� (the brain stem and cerebellum).

While the detail Feinberg adds to our understanding is scientifically invaluable, in philosophical terms this is no astonishing discovery, just a confirmation of what Hume thought over 200 years ago: there is no thing which is you at all. Each of us is merely a bundle of thoughts, sensations and experiences. Pretty much the same view was held by the Buddha, who believed that there is no abiding self, just a series of connected conscious experiences. Neuroscience confirms this and explains the mechanics of this centreless self, but it certainly didn鈥檛 discover it.

What about free will? Surely neuroscience has taught us some serious facts about that? It is a popular view, most recently echoed by Sam Harris in The Moral Landscape, where he cites experiments by Libet and others which show that activity in the brain鈥檚 motor regions can be detected 350 milliseconds before a person is aware of deciding to move, and that some decisions can be predicted up to 10 seconds before people are aware of having made them. 鈥淎ll our behaviour can be traced to biological events about which we have no conscious knowledge,鈥� writes Harris. 鈥淭his has always suggested that free will is an illusion.鈥�

But even here, the philosophers were way ahead of the game. It has been obvious for centuries that if human beings are made entirely of physical stuff, and all physical stuff simply follows the laws of physics, then there is no room in human action for any causal power other than the motion of matter. So to go back to Libet, whether consciousness comes before, after or simultaneously with decision-making, the key point is that thoughts and decisions are produced by no more than a brain working according to the laws of physics.

What else could a decision be but the product of a combination of the present state of being, fashioned by the past, and the environment that a person finds themself in? From at least Hume onwards, many philosophers have understood that the only meaningful sense of free will is action free from coercion or force, not action exempt from the causal necessity of the physical world. To that debate, neuroscience adds nothing.

I don鈥檛 wish to disparage neuroscience. On the contrary, I am in awe of what is being discovered about the mechanics of mind. But it is simply a philosophical mistake to think that understanding more about the nuts and bolts of the basis of self and identity must add something to our fundamental understanding of what makes us the individuals we are. Some scientists agree. 鈥淚 don鈥檛 think the self is ultimately a scientifically tractable question,鈥� clinical neuropyschologist Paul Broks told me while I was writing The Ego Trick.

The main reason is that the very notion of a science of the self depends on us identifying its subject 鈥� the self 鈥� from the perspective of first-person experience. Science can correct false beliefs about what sustains that experience, and it can explain what makes such experience possible, but it cannot change what it means to be a self without erasing the very data it depends on.