Man is three in one: a physical system, a living creature and a conscious mind. But how are they related? Neuroscience gives us some — but not all — the answers
As you read this, you are gradually consuming the oxygen that surrounds you. Don’t worry: it constitutes 21 per cent of the ocean of air we inhabit, and the supply is almost certainly sufficient for your needs. But were the indispensable “fire air” — in which Joseph Priestley noticed that “a candle burns with an amazing strength of flame” — suddenly to be removed, your consciousness, and then your life, would fail almost as fast. We are pathetically dependent on a constant stream of this life-giving gas. It reminds us that, whatever else we may be, we are thoroughly physical systems. We are the matter that composes us: the laws that govern our atoms also govern our lives.
But, of course, you are no mere assemblage of atoms, no mere morass of molecules. You are a needy, vulnerable, hungry, thirsty, breathing, palpitating, sickening, and — I would it were not so — ultimately mortal creature. Were your cells suddenly to falter in their ceaseless but unnoticed processes — as if lightly dosed with cyanide — your life would falter also. So, cataloguing the atoms that compose you does not suffice to understand our nature; we need to know something of life — the intricate network of processes through which we use energy from the environment to grow, maintain and reproduce ourselves. Though we tinker with it, we cannot finally escape the fate that our biology decrees.
And, of course, you are something more than a mere organism. You could not be reading these words unless you were the fortunate possessor of a mind — perceiving and pondering, planning and remembering, imagining, communicating, acting. If your mind failed you — as it can in depression or psychosis or dementia — your life might fail you also. “For seeing we are not maisters of our owne affections, we are like battered Cities without walles, or shippes tossed in the sea, exposed to all matter of assaults and daungers, even to the overthrow of our own bodies”, wrote the 16th-century physician, Edward Jorden. Our lives are guided by the light of our agile minds.
Each of us, then, is a physical system, a living creature, a conscious mind, three in one and one in three — and Hippocrates was right: “to know the nature of man, we must know the nature of all things”. But how are these three great ingredients of ours interrelated?
In the 19th century many thinkers, like Pasteur, the French microbiologist, regarded the emergence of life from matter as an unfathomable mystery, the expression of an élan vital. Nowadays just about everyone accepts that rather than being an irreducible mystery, life is simply the set of processes that allows organisms to use energy from their surroundings to reproduce themselves. Rather than being one unfathomable thing, it is the coherent operation of a great many intricate but thoroughly fathomable things.
Although we mostly accept that life emerged from matter by natural processes, many of us are more reluctant to accept that mind also emerged from living things by natural means. Here the notion of élan vital lives on: we hunt for a magic formula that will conjure “the wine of experience from the water of the brain” — and are somehow perversely consoled by the sense that it won’t be found.
There has, of course, been progress. Neuroscience can nowadays can give a fascinating, if still incomplete, account of what makes the difference in the brain between wakefulness and sleep; of how we sense the world; of how we learn, remember and communicate; of our emotions and our drives; of how we allocate attention, plan our actions, implement them. Even the most elusive yet most precious elements of our experience are becoming accessible to science. As you gaze at the face of your true love, areas linked to critical social appraisal fall quiet; calling an image to the mind’s eye, the brain produces a soft echo of what happens when we see; illusions of movement result from perfectly real activation of regions of the brain that signal motion; a shiver down the spine from a favourite moment of music expresses strong activation in the circuitry of emotional — and sexual — reward; the eerie experience of déjà vu arises from inappropriate activity in areas of the brain that tag familiarity.
Discoveries like these suggest that, as we learn more about the brain, we should become able to show that experience tracks its activity, hugging it curve for curve. Yet many of us remain unsatisfied — like Leibniz who, early in the 18th century, imagined walking into an artificial mind and finding nothing that could explain experience: “supposing there were a machine so constructed as to think, feel and have perception, we could conceive of it as enlarged and yet preserving the same proportions, so that we might enter into it as into a mill. And this granted, we should only find on visiting it, pieces which push against one another, but never anything by which to explain perception.” This is the “hard question” of consciousness, the “explanatory gap”: how can what happens in a brain ever give rise to what passes through a mind? It is the problem that the tough-minded physiologist Charles Sherrington described as an “embarrassment” for biology. To his frustration he could not see the way to a solution, and lamented: “to man’s understanding the world remains obstinately double”, a double act of matter — life and mind.
The solution is still uncertain, but two lines of thought look promising. First we need to ask ourselves whether we are really clear what it is we are asking science to explain. “Mind”, “awareness”, “experience” and “soul” are scarcely terms of science: our understanding of them is permeated by millennia of religious and philosophical thought and assumptions. We are intensely imaginative creatures — indeed, the capacity to detach ourselves from the here and now, to lose ourselves in imaginings, is one of our most characteristically human traits. We need to ask whether some things we tend to take for granted about our mental lives may be imaginative fictions. For example, the comforting and tenacious idea that we are animated by an invisible, immaterial, imperishable soul remains profoundly influential — even, I suspect, for those of us who accept that it is no more than a wonderful myth. It is liable to send us off in pursuit of a “neuroscience of the soul” that is sure to disappoint us.
The second line of thought is linked. When we gaze at the brain and ask how its 100 billion nerve cells can give rise to experience — rather as Aladdin’s lamp produces its genie — we may be depriving ourselves of just the resources we need to understand our mental lives. In the ordinary way, brains are not conscious — people are. The brain enables consciousness, for sure, but perhaps our metaphors mislead us when we ask how it “generates” it. Typically the life of the mind is “embodied, extended and embedded”: our brains interact with our bodies, our bodies move through our surroundings over time, and our experience is embedded in the culture that shapes it. Trying to explain human experience without reference to our human bodies, our physical surroundings or our culture may be asking too much of the brain.