In severing the mind from the world, Rene Descartes severed the mind from its body. As a consequence, the role and even existence of mind became problematical. How are mind and body related? Do minds exist? Are there other minds?
How Are Mind and Body Related?
The first question asked was how mind and body could interact. Descartes assumed they did: the body provided the soul with a window on the world, and the soul exercised control of the body. However, he did not satisfactorily explain how they interacted. During the nineteenth century, most psychologists adopted Leibniz’s psycho-physical parallelism. Although this position conveniently gave psychologists their own realm, consciousness, to study, it left nagging problems, such as why mind and body seem to interact, and the value of studying an impotent mind. By the end of the century psychologists began to replace the seemingly pointless introspective study of an impotent mind with the more useful study of behavior.
Do Minds Exist?
One apparent solution to the problem of mind-brain interaction was materialism, denying that minds exist. As the century unfolded, scientific advances made dualism less, and materialism more, plausible. The challenge of materialism was most acute for psychologists in the empiricist camp. Believing that mind was more fundamental than matter, idealists saw materialism as a pernicious error to be defeated, but for the scientific prospects of psychology, idealism had the drawback of setting the transcendental ego outside investigation. Empiricism had a different drawback. Empiricist psychology identified mind with consciousness, which had the virtue of making psychology a natural science. However, because it was a surface floating over the brain, not the self, consciousness might simply be a brain process, and psychology might someday vanish into physiology. Idealism suggested that psychology was not a science, whereas empiricism and materialism suggested that it was a temporary one.
The specter of materialism haunted psychology throughout the century. When Gall declared that the brain is the organ of the mind, the way the stomach is the organ of digestion, he and his followers were denounced as dangerous materialists. In the later nineteenth century, when scientific psychologists began to link consciousness and brain, they, too, were suspect in the eyes of many. In the United States, for example, the “old psychologists” (followers of the Scots) feared and denounced the “new psychologists” (the German-inspired experimental physiological psychologists) for neglecting the care of the soul, which for them was the proper mission of psychology.
Controversies over Darwinian evolution were linked to materialism. Descent of humans from animals suggested that we, too, are soulless machines. Darwin’s bulldog, Thomas H. Huxley (1825-1895) famously (or notoriously) declared that consciousness is a useless byproduct of the brain’s activity. James rejected this automaton theory in his Principles of Psychology (New York. 1890), arguing that consciousness’s adaptive function was choice. Ultimately, however, he abandoned psychology for philosophy, in part, because he could not reconcile his faith in free will with his conviction, expressed in Principles, that as a science, psychology must be “cerebralist,” committed to tightly linking mind and brain. James later became heavily involved in psychical research, the paradoxical endeavor to use scientific means (empirical research) to prove a religious point: the existence of the soul.
Much of the seeming threat of materialism stemmed from the reigning conception of machines. If one accepts the Cartesian idea that animals are machines, and then concludes with Darwin that we are but animals, one seems forced to conclude that we are machines having no control over our behavior. Purpose (flexibly pursuing a goal when faced with obstacles) seemed, like David Hume’s vanishing self, to be an illusion in need of explanation. This viewpoint was held by most behaviorists in the twentieth century.
However, the computer has destroyed Descartes’s image of machines as clockwork mechanisms. A chess-playing computer program has a purpose (winning) and generates possible moves from among which it chooses the most promising. Seeing humans as machines—as cognitive science does today—is not inconsistent with seeing them as having goals and exercising choice. However, the computer model of the mind has not solved the problem of conscious experience. It remains unclear how matter generates consciousness. More radically some ask, as James did in 1905. “Does consciousness exist?”
Are There Other Minds Than Mine?
In severing the mind from the world and from the body, Descartes made the existence of other minds problematical. In the Cartesian view, mind is private consciousness. But how do I know if other beings have minds? Descartes would answer: I know within myself that I think and that I express my thoughts in language. Therefore, any creature possessing language also possesses a thinking soul. Because only humans have language, only humans have souls.
In the nineteenth century, evolution erased Descartes’s bright line between man and animal. Animal psychologists, led by George John Romanes (1848-1894), Conwy Lloyd Morgan (1852-1936) and Darwin himself, began looking for mind in animals, creating the field of comparative psychology. They soon had trouble reconciling what they found with Cartesian mechanism. Animals do not react to stimuli with unchangeable reflexes, but can learn new adaptive behaviors to attain their goals. The first comparative psychologists believed that animals as well as humans have consciousness (mind) and are therefore not machines. Some important early twentieth-century psychologists, such as Edward C. Tolman (1886-1959) agreed, although they referred vaguely to purposes and cognitions rather than to mind or consciousness. Nevertheless, most psychologists followed Edward L. Thorn-dike (1874-1949) and Clark L. Hull (1884-1952), who asserted that animals (and humans) are machines. They proposed stimulus-response reflex theories of behavior that explained purpose away.