OM 3-1: A Historical Overview of the Mind-Body Problem

Throughout history, many scientists and philosophers have contemplated how to define the subtle and remarkable mind. The analysis of the relationship between consciousness and the brain is known in Western thought as the "mind-body problem."

We have seen that consciousness cannot be accounted for in physical terms, but that still leaves open many questions. What exactly is consciousness, and how is it related to the brain? If it is simply a product of the brain's higher neural centers it may be possible to account for it by a nonquantitative description of the brain. Or could it be that consciousness is associated with a separate entity connected with the brain? In Western thought, the words mind and self have been used interchangeably to name this entity. For the time being, therefore, we shall also use the words mind and self in this specific sense. But we shall later point out a fundamental distinction between the mind and the conscious self.

Traditionally, Western thinkers have regarded consciousness or mind as nonphysical and distinct from the brain. One well known mind-body theory of this type was presented by seventeenth-century French mathematician and philosopher Rene Descartes. His dualistic conception postulated two kinds of substances-mental and corporal. The essence of a mental substance is that it has thoughts and is conscious of them, and the essence of a corporal substance is that it has position in space. Mind and matter can and do interact and influence one another; matter influencing mind is called sensation, and mind influencing matter is called the exertion of will. Thus his theory became known as interactionism.

Descartes reasoned that mind, as a nonphysical substance, would not occupy position in space. But his opponents insisted that a mind without position in space would be unable to influence the material body, which has a position in space. This was a criticism that Descartes never effectively countered.

One reason for Descartes' failure was the way he conceived of the mental substance. He assumed that if something has certain fundamental characteristics that cannot be described in physical terms, then all of its properties must be beyond physical description. But it is within the realm of possibility that a nonmaterial substance could also possess some properties that can be placed within the framework of material measurement.

For instance, there is no logical reason to exclude the possibility of a nonmaterial mental substance having position and being able to interact with the brain. But opponents of Descartes' theory, among whom may be numbered most physicists, strongly reject such interactionism because it would violate the laws of conservation of energy and momentum. If a nonphysical entity, the mind, influences the brain, it would tend to alter the brain's energy states, a phenomenon physicists would find unacceptable because it clashes with their equations defining the laws of physics. These equations specify that matter moves solely according to causes governed by physical laws. If nonphysical causes and laws were involved, the equations of physics would no longer suffice to describe the movements of matter.

Here we might point out that as of yet no one has proved that all matter obeys only the physical laws. In particular, no one has ever offered a complete mathematical description of the brain and its functions. Within the human brain there are one hundred billion nerve cells. No one can possibly trace out or monitor all the energy transfers in the brain. Therefore the physicists' objection to interactionism is simply not valid, and is fostered by a desire to impose a particular, restrictive view of the mind's relationship with the brain.

Before Descartes practically all thinkers accepted that the mind or self was different from the body or brain. Descartes attempted to formulate this dualism in such a way as to overcome the objections of those who were being influenced by the rise of mechanistic science, which had no room for nonphysical substances. But his explanation left so many questions unresolved that most thinkers approaching the mind-body question after Descartes gave up interactionism.

Others made cautious efforts to formulate dualistic models that did not interfere with the known laws of physics. One such idea is epiphenomenalism, the proponents of which include Darwin's champion, Thomas Huxley. Epiphenomenalism presents what seems to be dualism of the mind and brain, but is really an attempt to maintain the superiority of mechanistic views by employing a highly unusual model. Epiphenomenalism states that matter gives rise to a nonphysical consciousness, but these states of consciousness have no influence on matter. This model has two major shortcomings. First, it doesn't explain how consciousness could arise from matter. Second, the idea that consciousness doesn't act upon matter is extremely awkward. In physics, all aspects of a physical system have some effect on the behavior of the total system. Why should consciousness be an exception?