Soul searching

What have advances in neuroscience told us about the mind?

Soul Made Flesh: The Discovery of the Brain and How it Changed the World

Free Press: 2004. 384 pp. $26 To be published in the UK by Heinemann in April, £17.99 0743230388 0434010464 | ISBN: 0-743-23038-8

The provocative title of this book alone, Soul Made Flesh, made me want to read it. After all, we live in a time where scientists are doing their best to explain all mental phenomena in terms of matter. Advanced medical technology, such as the magnetic resonance imaging (MRI) scan, makes the processes of the brain visible and gives us the feeling that we are gaining an insight into the nature of the mind and its functions. Even more, we are relieved when psychological disorders can be explained in terms of a malfunctioning brain. It enables us to ascribe our depressions and mania to something alien that is not essentially part of our true selves.

Carl Zimmer's fascinating book shows that what we think of as recent developments began in the seventeenth century, when the English anatomist Thomas Willis began dissecting brains in Beam Hall at Oxford. At the beginning of the seventeenth century, the brain was seen as a ‘bowl of curds’, functioning as a kind of refrigerator to cool the heat of the blood. By the end of the century, thanks to Willis, the brain was studied as the seat of emotions, perception and memory.

Surprisingly enough, Willis is largely unknown. Some might remember him as the discoverer of the so-called ‘circle of Willis’, a ring of blood vessels at the base of the brain, but it is not widely known that his descriptions of the brain and nerves are at the root of modern neurology. According to Zimmer, this is because John Locke's ideas eclipsed those of Willis. Locke argued that we cannot know much about the inner working of the mind, so we should restrict ourselves to the ideas themselves and how they are confirmed by everyday experience. Willis, on the other hand, showed that the anatomy and chemistry of the brain could reveal the working of the mind — an idea that was dangerous at the time because it smacked of atheism.

Yet, Willis managed to keep out of theological trouble by strictly separating the immortal, rational soul from its bodily counterpart, the sensitive soul. The latter, Willis argued, consists of tiny particles that function as messengers, conveying sense and motion from the brain via the nerves to the rest of the body, and vice versa. Illness is caused by miscommunication and damage to the brain. Most notably, Willis was able to explain psychological illnesses and disabilities resulting from brain damage.

Zimmer's book is fascinating, not least because it provides a vivid picture of the world of which Willis was a part. Not only does he describe the smells of seventeenth-century Oxford in a way that transports you right there, but he also convincingly explains Willis's work in its political and religious contexts. We meet Oliver Cromwell and his puritan followers as well as King Charles II and his curiosity for the new experimental natural philosophy. Thomas Hobbes and Lady Anne Conway also figure in the story. Last, but not least, the reader is made part of the audience watching the often outrageous and crazy experiments of the so-called Oxford experimental circle — a group of natural philosophers busy with topics as diverse as submarines, blood transfusions, spacecraft and vacuum pumps.

Historians of science have written extensively about seventeenth-century English natural philosophy. Yet making sense of the diverse experiments of the Royal Society and its forerunners remains a tricky enterprise. Historians usually focus on one or two philosophers, a series of experiments or a particular philosophical movement. Zimmer's book is remarkable in that it offers a multifaceted picture of the world and work of Willis. In so doing he has managed to make sense of Willis's ideas in turbulent times of revolution, plague and fire.

In the final chapter, Zimmer moves from the dissection room in seventeenth-century Oxford to a present-day MRI investigation at Princeton University. He introduces us to the philosopher Joshua Green, who is interrogating someone in the machine while he looks at depictions of the brain on his computer screen. The aim of his research is to establish a better understanding of the nature of moral judgements. The soul made flesh — it is an eerie reality of modern neurological and philosophical research. To my taste, Zimmer does not sufficiently distinguish Willis's concept of soul from its twentieth-century counterpart. For Willis, the concept of soul referred to the processes of life at large, whereas nowadays we associate the soul with mental functions.

In the seventeenth century, people tried to cure diseases of the mind by manipulating the brain and nervous system. It is this continuity of concern that makes Zimmer's book such a fascinating read.

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Knoeff, R. Soul searching. Nature 427, 585 (2004).

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