Mind, Brain, and the Limits of Science

What Makes Us Think? Jean-Pierre Changeux and Paul Ricoeur. New Jersey: Princeton University; 2000. 336 pages. $29.95. ISBN: 0691009406

Several years ago, a PET scan was published showing selective activation near language regions of the cortex during silent speech. For the first time in history, observers could see directly what happened in the cortex when subjects were asked to speak to themselves. There was no fanfare; very quietly, a hotly debated, century-long controversy about the role of inner speech in thinking was laid to rest. Psychologists had long argued whether thought involves subvocalization. Although one could simply ask people at random moments during the day whether they were silently talking to themselves (they generally said yes), controversy continued for decades, for reasons that were perhaps not purely scientific. A single brain scan experiment in the 1990s put the matter beyond dispute.

Inner speech is the most private realm. It is the domain in which we defend ourselves against unjust criticisms from friends, foes, and loved ones. It is the arena of grandiose sexual and aggressive fantasies we do not share with others, and sometimes not with ourselves. It is the tiny inner world in which we justify our actions to imagined audiences—parents, siblings, grant reviewers, gods. Nothing is more personal. What does it mean, therefore, when science can peek into our most private nooks and crannies?

In many ways, brain imaging is actually a mixed blessing. As scientists, we assume that knowledge is better than ignorance. In the long run, people will be healthier and more comfortable as a result of major brain advances: neuroimaging, a detailed molecular understanding of neurotransmitters, genetic regulation of hormones, stem cells, and much more.

But we rarely consider the costs of such advances—how much we are asking people to give up. Every major scientific advance since Copernicus has caused intense distress for ordinary people. Traditional beliefs are thrown overboard, relationships undermined, comforting convictions drained of meaning. Darwin is considered a scientific giant, rightly, but he was acutely aware of how educated families in England broke apart within generational conflict as a result of his ideas. The social turmoil continued for decades after the publication of The Descent of Man (1862). Today, turmoil still goes on, all over the world, as traditional cultures confront modern science; the very insights of science dissolve traditional cultures.

Brain discoveries are likely to promote this type of cultural turmoil in our time, because they touch on the most intimate beliefs people have, notably our sense of free will. They undermine the human yearning to believe in a personal soul, free from the decay of the body. In philosophy, the twentieth century was characterized by a behavioristic denial of free will, but at the same time philosophers carried out a fierce attack on scientific efforts to understand the conscious mind. Many of the controversies of the last hundred years no longer seem strictly scientific; they now seem to have been driven by a deep need to defend traditional beliefs about mind and will. In many cases (like the reality of inner speech) the evidence was there all along. But it is extraordinarily difficult for human beings to study our own minds dispassionately, the way we might look at a rock or a plant. Brain imaging and other techniques now introduce scientific evidence into the old impassioned debates.

These thoughts come to mind upon reading the remarkable dialogue between the well-known neurobiologist Jean-Pierre Changeux and Paul Ricoeur, a famous French philosopher, in their book, What Makes Us Think? This kind of dialogue could probably not happen today in the English-speaking world, for Changeux and Ricoeur have obviously talked with each other not just once, but many times, perhaps for years, and this book presents thoughts hammered out in those conversations. They speak in depth not only about philosophy and brain science but also anthropology, sociology, politics, art, religion, and ethics. They quote liberally and precisely from philosophers, French, German, and Anglo-American, and from scientists in fields like child development, social psychology, and brain science. Their historical memory goes from the Greeks, Buddhism, and the Bible to Darwin and Lavoisier. They carry all the expected knowledge and assumptions of French intellectuals, perhaps the last national elite thinkers.

Jean-Pierre Changeux seems to have the advantage in the first half of the dialogue. As a neuroscientist, he is in a remarkably good position today to speak about mental processes, based on a vast body of evidence, including the effects of attention and consciousness, even schizophrenic hallucinations and fear. Changeux presents brain images in combination with other evidence, carefully and clearly.

Philosophy has been a center of resistance to the apparently relentless onslaught of scientific beliefs. For centuries, philosophers “owned” basic mental processes. Today, they have retreated to a largely defensive stance, telling us how difficult it is “in principle” to explain mental events by reference to the brain. Paul Ricoer argues time and again that the “discourses” of mind and brain are different and incompatible, that mind cannot be understood by neurons and molecules. But as Changeux shows each time, we now have detailed evidence for brain processes that were previously knowable only through introspection and behavioral inference. The two discourses of mind and brain are no longer separable. Very quietly, two worlds are beginning to merge.

But an odd shift occurs in the middle of the dialogue, when Changeux begins to sound a theme that is evidently close to his heart: the theme of ethics. For Changeux is a child of the Sixties in France, especially of the political turmoil of 1968 when students took to the street in protest against yet another ancien régime. A distinguished scientist, he has never fully left his passionate involvement in politics and ethics (and, he seems to hint, in religious matters as well). Scientists are members of a wider culture, too.

In reading the dialogue, I found the scientist Changeux to become less and less persuasive, the more he touches on ethics and politics, even though my values are not much different. I think that peace is better than war and that human well-being is a worthy aim. I just don’t think the proof procedures of science extend to ethics or politics. In science, we aim to demonstrate propositions by an appeal to evidence. But there is no scientific evidence proving that life is “better than” death, comfort is “better than” pain, or that progressive intellectuals are “better than” the hidebound bourgeoisie. The persuasive force of PET scans and immune assays does not extend to political arguments. Ethics and values are truly a different “discourse,”not just because their language and assumptions are different, but also because evidence, with its direct bearing on propositions about reality, has little bearing on values. Human cultures and individuals display a fantastic array of diverse and contradictory values in life. Changeux cannot prove to the warrior Yanamamo tribe that destroying their neighboring village is wrong, certainly not by objective evidence.

There is a lesson of sorts in this for scientists. Through brain and behavioral science we have opened a door, for the first time in human history. We can begin to look into the minds of human beings in the act of being themselves. The possibilities are endless. And yet, when it comes to using those discoveries for good or ill, scientists are in no better position to judge than anyone else. We have no privileged insights into ethics and values, no proof procedures that will persuade any rational person that one course of action is better than another. As a result, we must live with the unintended consequences of our own discoveries, like it or not.

• © American Society for Pharmacology and Experimental Theraputics 2001