The Path of Consciousness

The Astonishing Hypothesis: The Scientific Search for the Soul.
by Francis Crick.
Scribner’s. 317 pp. $25.00.

Some 40 years ago, in a Nobel Prize-winning feat, Francis Crick and James Watson unraveled the structure of DNA, showing how the genetic information which controls the biological nature of all living creatures is stored in a molecule with the shape of a double helix. Unburdened by false modesty, Crick proclaimed in a Cambridge pub: “We have discovered the secret of life!”

Since then, Crick’s ambition has not waned. Now in his late seventies, having moved from Cambridge to California and changed his focus from biochemistry to brain research, he believes that the time is ripe for a rigorous exploration of the phenomenon of consciousness—or, as he puts it, a scientific understanding of the human soul.

In his new book, Crick proposes what he calls an “Astonishing Hypothesis.” Saving the reader undue suspense, he states it in the first paragraph of his introduction:

You, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.

If this hypothesis is correct, Crick goes on, it follows

that the idea that man has a disembodied soul is unnecessary . . . in head-on contradiction to the religious beliefs of billions of human beings alive today.

A question immediately pops into mind: in a world full of atheists, agnostics, and diehard skeptics, what is so astonishing about this hypothesis? And in fact Crick agrees that many people today (“including a large number in the former Communist countries”) do dismiss the idea of a nonmaterial and perhaps immortal soul. Yet, he argues, despite paying lip-service to a materialistic explanation of the mystery of human existence, few people really accept it in their hearts. Almost all of us still think of ourselves as having an essential core different from the sum total of the activity of all our nerve cells (neurons). We feel the presence of an internal “I”—a virtual miniature man or homunculus sitting inside ourselves—that observes the external world, tries to make sense of it, and embodies the free will that decides how we should act.

It is that intuitive feeling, says Crick, which is an illusion, generated by the immensely complex nature of the brain and nervous system. Although we are far from understanding enough about the workings of that system to explain the phenomenon of consciousness, Crick believes it is time for a concerted scientific attack on the problem. In this book he summarizes what is known today about the workings of the brain, describes the methods used by researchers to learn more, suggests further questions for investigation, and theorizes about the purpose of consciousness and how it arises.

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Crick believes fervently that the only reliable source of knowledge is scientific investigation, a method of solving complex problems by breaking them down into a set of simpler questions, answerable in terms that can be tested experimentally. As an extremely successful practitioner of this methodology, he suggests that the scientific investigation of consciousness should begin with a detailed study of vision, which lends itself more easily to experimentation in both humans and animals than does speech (even though it is precisely verbal ability that most distinctly separates man from beast and enables him to express his consciousness).

What, then, do we know about the visual system in mammals? Both a great deal and very little. As Crick points out, the structure and functioning of the eye, the molecular biology and chemistry of individual optic nerve cells, and the psychological mechanisms that help us decide what to look at and how to interpret the often ambiguous messages we receive from the outside world have all been explored. But even with this mass of knowledge, we really have no idea how the visual system manages to extract order from the incredible number of individual pieces of visual data that bombard it every second.

As with the eye in particular, so with the brain in general. One of the great virtues of this book is the very full account Crick provides of the ingenious techniques scientists have developed to overcome some of the incredible difficulties involved in studying the brain, a compact mass that contains half the neurons in the human body. To try to make sense of the way these tens of billions of cells act, both individually and collectively, researchers use instruments ranging from massive CAT, PET, and MRI scanners that look at the whole brain or local areas within it to fine glass electrodes sensitive enough to detect chemical and electrical activity in a single neuron (with a diameter less than one-thousandth of an inch). They study the effects of different stimuli on normal brains in animals and humans, both sleeping and awake, and on damaged brains. Some scientists study the properties of slices of brain tissue growing in dishes, while others study optical illusions in order to make inferences about the way the brain connects raw inputs to final perceptions.

Generally speaking, much more is known about what happens at the beginning and end of the process—the input of raw sensory data and the conclusions our brain gives us—than about the complex chain of internal events in-between. As Crick would put it, we have no neurons whose firing tells us what is going on in the brain. The scientific description he seeks is thus precisely one that will specify the “neural correlates” of mental activity—the actual physical and biochemical processes that produce our thoughts.

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While waiting for that breakthrough, Crick brings together here the knowledge contributed by psychology and physiology, biochemistry, electrical engineering, and recent advances in computer science (in particular, so-called neural networks) to construct his own model of consciousness. He explains it, in brief, as a consequence of “reverberatory activity” between different parts of the brain—the thalamus and the cortex—which serves as a kind of short-term memory, taking the output of large numbers of neurons, assembling a mass of raw data and making it into one package of usable information.

In a short postscript, Crick also expounds his theory that the brain contains an assembly of neurons devoted to making plans for future action; this assembly obeys computational rules “wired into” the brain by a combination of genetics and experience. Because we are not consciously aware of these rules, but only of the action-oriented outcomes they generate, and because some of them are extremely sensitive to small changes in their inputs, the decisions we make appear unpredictable, which is why we think we have free will. Basing himself on studies of a brain-damaged woman who was able to observe her surroundings and understand conversations, but unable to form responses, Crick opines with startling specificity that “Free Will [his capitals] is located near the anterior cingulate sulcus.”

And what of the soul? Some 256 pages after mentioning it in his introduction, Crick returns at the end to acknowledge that many readers “might justifiably complain that what has been discussed . . . has little to do with the human soul as they understand it.” Yet all such criticisms, he admonishes, though “perfectly valid at the moment, . . . show a lack of appreciation of the methods of science.” Once the working of the visual system is fully understood, science will go on until it is eventually able “to explain all aspects of the behavior of our brains, including those of musicians, mystics, and mathematicians . . . perhaps some time during the 21st century.” For those who still remain unconvinced—who still find something inexplicable about man and his soul—they are captives of a view “predetermined by a slavish adherence to religious dogma.”

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And how would they have come by such a view? Crick has an answer for that, too. Man simply cannot be anything more than the product of a random evolutionary process, edited by the pressures of natural selection. Thus, if we seem to behave and think in a way very different from the rest of creation, that must also be a consequence of Darwinian mechanisms. Even our religious beliefs are explicable in such terms:

It should always be remembered that our brains largely developed during the period when humans were hunter-gatherers . . . [with] strong selective pressure for cooperation within small groups. . . . A shared set of overall beliefs strengthens the bond between tribal members.

As long as people accept such shared beliefs, says Crick, they need not even be true. Precisely because “our brains evolved to guess the most plausible interpretation of the limited evidence available,” humans have an “almost limitless capacity for self-deception.” This, indeed, is why we need scientific research, for otherwise “we shall often jump to wrong conclusions, especially about rather abstract matters.”

Quite apart from their breathtaking condescension, what these lines neatly ignore is that there are, after all, many abstract questions which scientific research, no matter how disciplined, cannot answer, including some of particular importance to human beings. A major problem for evolutionary theory, for example, is how and why homo sapiens should have developed a propensity to pose abstract mathematical questions having nothing to do with the everyday observable world but leading nevertheless to the revelation of hidden truths about the way the whole universe works. Similarly, the human concern for moral questions leads to even deeper propositions about the nature and purpose of the universe, propositions that stand in sharp contrast to the idea of a random, amoral, Darwinian world.

Crick is correct to suggest that scientists are unlikely to discover the human soul, but not for the reasons he states. They are like expert mechanics who can disassemble every part of an automobile, explain how it works, and perhaps even repair it. Those activities are all very valuable to the car owner, but they cannot help him decide where he should drive, or why.