Are we just really smart robots? Two books on the mind put the human back into human beings.

• Author: Silber, Kenneth
• Position: Culture and Reviews - Book Review

On Intelligence, by Jeff Hawkins with Sandra Blakeslee, New York: Times Books, 261 pages, $25

Mind: A Brief Introduction, by John R. Searle, New York: Oxford University Press, 326 pages, $26

NEUROBIOLOGY'S advances generate anxiety as well as joy and hope. On the joyful and hopeful side, there are the prospect and reality of improved treatments for brain diseases and debilities. But anxiety arises over what the science tells us, or will tell us, about ourselves. Thoughts and feelings may be reduced to brain structures and processes. Consciousness and free will may be proven unimportant or illusory. Much of what we value about ourselves, in short, may be explained--or, worse, explained away.

The prevailing trends in the philosophy of mind reinforce such concerns. The field is dominated by schools of materialism that describe mental phenomena as types or side products of physical phenomena. Mind-body dualism, which posits a separate existence for the mind, has been effectively eclipsed (although it seems to receive continued implicit acceptance from many nonexperts). Some forms of materialism argue that the mental phenomena in question do not even exist.

This turn toward the mechanistic could have baleful cultural and political consequences. It threatens to undermine people's sense of responsibility and self-worth. There is the danger of what philosopher Daniel Dennett calls "creeping exculpation," as more and more human behavior is attributed to material causes. Criminal violence, for example, might be excused as a consequence of low levels of serotonin or monoamine oxidase in the brain. Many philosophers, including Dennett, argue that humans should be regarded as responsible agents even if human behavior is fully determined. But the very fact that such arguments need to be made shows how the deterministic premise has altered the terms of debate.

If humans are mechanistic beings, it becomes harder to understand why they should not be used as means to an end or why there should be much concern with what they are thinking or feeling. At a political level, such quandaries pose a threat to liberal democracy, which relies heavily on the assumption that we are autonomous beings with the capacity to make meaningful decisions. Mechanistic theories have enjoyed an authoritarian cachet in the past. Stalin's regime embraced the work of Ivan Pavlov, famous for conditioning dogs to salivate at the ringing of a bell. In Walden Two (1948), the American psychologist B.F. Skinner described a society whose managers use operant conditioning to suppress competitiveness and other undesired behaviors.

Alongside the conception of human beings as biological machines looms another specter: that human mental capacities will be equaled or exceeded by machines of our own creation. An influential doctrine in the philosophy of mind, congruent not only with neurobiology but with cognitive psychology and computer science, is computer functionalism. This view holds that the mind is fundamentally a computer program implemented in the brain's hardware--one which could be replicated in a different physical substrate. Notwithstanding the limited progress of artificial intelligence (A.I.), many experts expect it to achieve vast advances in coming decades. More important, the general public expects this too. The prospect arouses considerable anxiety, as reflected in the Terminators and Matrixes that populate science fiction.

The scientific and philosophical quest to understand human beings as part of the natural world thus seems to come with a hefty price. It forces us to regard ourselves as mere machines--indeed, as potentially obsolescent machines, given...