The hypothesis that the soul and the body are separable is as old as the dream of an afterlife. In early Greek days, the soul was identified with ‘pneuma’ or breath. Watch someone die and you will see a last exhalation. People believed that the soul of the dying departed the body with that last breath, and, just perhaps, went somewhere else. The fear of death, literally a fear of ‘nothing’, seems to be the other side of loving life. It is an animal fear that finds a characteristically human response. Entertaining hopes of an afterlife is very understandable, especially considering that death is mysterious and we cannot know with absolute certainty what happens after we die.
In Western philosophy and religion, the soul-body split is maintained as an article of faith for many centuries. With Descartes, in the early modern period, the soul morphs into a ‘mental substance’. In his metaphysical dualism, the Christian ‘soul’ becomes ‘cognitivized.’ The mind becomes identified with ‘thinking’ and ‘immediate self’-awareness’.
Descartes’ way of distinguishing mind and body has a certain plausibility. Otherwise, his theory would not have been taken seriously. The mind, and things mental, do not exist in space or have parts with spatial dimensions. Mental objects exist without doubt in our subjective appreciation of them. Each mind is a true individual, while bodily things have no absolute identity, being just thicker or thinner parts of one huge material substance. Minds and bodies are bearers of completely incompatible properties, and thus refer to separate metaphysical substances.
From this high point, there can only be questions, and Descartes, himself, starts the process. For example, he said that the soul is not in the body the way a captain is in his ship. There is some kind of substantial unity of mind and body. In addition, he thought it obvious that we are all aware of thoughts causing physical reactions, and bodily events causing changes in thinking and feeling. Thinking, here, involves everything of which we have direct awareness, like our perceptions, sensations, emotions, thoughts, mental images, and so on.
The famous problem with Descartes’s theory is that there seems to be no way to explain the substantial unity or the interaction of mind and body. He undermines his own theory by attempting to explain the connection in terms of ‘animal spirits’ that are based in the pineal gland but spend their time taking messages from the body to the mind or vice versa.
Opposed to this dualism are various forms of monism claiming that we merely describe one substance in different ways. However plausible, there is something missing from an approach that starts from the position that dualism must be overcome with a theory of direct reconciliation or identification of mind and body. Of course,working from the naturalistic principles common today, we cannot have the soul flying off somewhere after the death of the body. Aristotle is reasonable about this. Mind (nous patheticon) is the idea of a living body of a certain complexity. Without that living body, the individual’s mind is gone. Naturalism is incompatible with an invisible after life.
This is reasonable, but we would do well to shift to another way of thinking about the mind-body problem. Instead of looking at it as a problem of separate entities that must be reconciled, we might try looking at the mind and body as part of a system. This system includes more than cognition and bodily properties. We are speaking of human beings here, and we need a dynamic and systematic understanding of them, not one that can be captured in a still picture.
Humans exist in time and history. We cannot abstract their ‘minds’ and their ‘bodies’ from the complex and interactive world in which they live. The concepts of ‘mind’ and ‘body’ are too bare to support a systems approach. I therefore propose to jump over all the arguments about the sameness or difference of mind and body, and try to formulate a way of conceiving them as belonging to a dynamic system in which philosophy, psychology, behavioral economics and neuro-physiology will play a part in deepening our self-understanding, thus obeying the philosophical injunction to know oneself.