I am not a physicist, professional philosopher, or interested in participating in the massive and fiery atheist v gnostic feud that takes place all over the internet every day.
I just finished reading a post by Sean Carroll over at Discover’s physicist and astrophysicist blog Cosmic Variance. Sean writes:
Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there’s no way within those laws to allow for the information stored in our brains to persist after we die. If you claim that some form of soul persists beyond death, what particles is that soul made of? What forces are holding it together? How does it interact with ordinary matter?
Everything we know about quantum field theory (QFT) says that there aren’t any sensible answers to these questions. Of course, everything we know about quantum field theory could be wrong. Also, the Moon could be made of green cheese.
He slaps down the Dirac equation, the rather triumphant mathematical union of quantum mechanics and special relativity. He asks: What would you change to make the soul fit?
Carroll’s objection is not new. It is, in essence, an updated version of the argument made by Princess Elizabeth of Bohemia (1618-1680) in her letters to Descartes in 1643. In Treatise of Man, Descartes identified the pineal gland as the “seat of the rational soul,” where (much like Carroll’s “blob of spirit energy,” which “drives around our body like a soccer mom driving an SUV”) it receives sensory information from flowing “animal spirits” and controls the body’s movement through interactions with the ventricles.
Descartes picked the pineal gland because it was singular, central, and small enough for the spirits to move it around:
“My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed. The reason I believe this is that I cannot find any part of the brain, except this, which is not double. Since we see only one thing with two eyes, and hear only one voice with two ears, and in short have never more than one thought at a time, it must necessarily be the case that the impressions which enter by the two eyes or by the two ears, and so on, unite with each other in some part of the body before being considered by the soul. Now it is impossible to find any such place in the whole head except this gland; moreover it is situated in the most suitable possible place for this purpose, in the middle of all the concavities; and it is supported and surrounded by the little branches of the carotid arteries which bring the spirits into the brain” (29 January 1640, AT III:19-20, CSMK 143)
Princess Elizabeth’s objection was one having to do with Descartes own distinction and their (shared) contemporary understanding of physics: How does a substance not extended in space exert an influence on physical objects extended in space? The problem raised in her letters was one of soul-brain interaction:
“I beseech you tell me how the soul of man (since it is but a thinking substance) can determine the spirits of the body to produce voluntary actions. For it seems every determination of movement happens from an impulsion of the thing moved, according to the manner in which it is pushed by that which moves it, or else, depends on the qualification and figure of the superficies of this latter. Contact is required for the first two conditions, and extension for the third. You entirely exclude extension from your notion of the soul, and contact seems to me incompatible with an immaterial thing.”
Although our understanding of the physical world has increased quite a bit since 1643, Descartes was unable to coherently respond to this challenge within the framework of the time (he suggested that the Princess conceive of the soul as extended, even if it really is not, and suggested that the soul’s ability to change the physical is simply an empirical fact).
How can the soul move an electron, something in an exhaustively equation-defined system, without being a part of that system (a term in the equation)? If Descartes was alive today, he would probably be worrying about other things.