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According to Cartesian dualism, the mind is an immaterial substance that do not have spatial extension whereas the body is made up of spatially extended material substance. This dichotomy has created a difficult problem: how can the mind drive body's movement? In a 1643 letter to Descartes, Princess Elizabeth of Bohemia wrote:
Here the word "soul" means "mind". The two words were often used interchangeably at that time.
The Role of Pineal Gland
Descartes did not directly address the issue raised by Princess Elizabeth. Instead, he proposed that the pineal gland should play a central role in the mind-body interaction. This view was based on the following argument (Stanford Encyclopedia of Philosophy):
Descartes postulated that the movement of pineal gland might change the tension of muscles, thereby resulting in bodily movement. The pineal gland could be moved either by sensory stimulation or the force of soul (mind).
The Role of Striatum
Although modern neuroscience did not find any motor system connected to the pineal gland, Descartes' basic idea could be right: there could exist in the brain a specific area responsible for the mind-body interaction. Compelling evidence indicates that such area is the striatum which has been demonstrated to play a central role in action selection. Details are described in Chapter 11. Before that, we should know first what the mind is, and where the feeling of pain and pleasure comes from. Then we could explain the animal behavior, "seek pleasure, avoid pain", on the basis of well-established neural circuits connected to the striatum. Not only can the issue raised by Princess Elizabeth be resolved, the Geon Hypothesis further explains how the pleasant feeling drives the action of "seek" and how the painful feeling propels the movement of "avoid".
According to the Geon Hypothesis, the mind comprises a huge number of gravitational and electromagnetic waves. The next chapter will briefly introduce these waves. Chapter 5 will discuss gravitational waves in more detail.
Author: Frank Lee