Today, we know that the pineal gland, located deep within the brain, secretes the hormone melatonin, which helps us sleep. But three centuries ago, René Descartes believed it was where mind and body interacted. By ‘body,’ he meant things that had weight and three dimensional “extension” (took up space), and this included the brain, which occupies about eighty cubic inches and weighs around three pounds. On the other hand, the “furniture” of the mind lacks volume and heft. Thus, it makes no sense to ask, “How many inches wide is that fear?” or “Did that inspiration weigh more than a pound?” So the physical world is one thing, the mental world another, but they’re not insulated from one another, and, for Descartes, the pineal gland is the transfer station, the key to “interactionist dualism.”
The notion of two separable components is captured in such songs as I’ll Fly Away:
Some bright morning when this life is over
I’ll fly away
To that home on God’s celestial shore
I’ll fly away
It echoes the message of Psalm 70:10: “The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away.” In other words, like John Brown (in Pete Seeger’s words), our bodies may be “mouldering in the grave.” Nevertheless, “we” (minds) will fly away (from our bodies) to something much better.
As with virtually every claim in philosophy, options, rivals, and critics abound. Among those in play have been:
- Materialism, which claims that there’s only body, just the physical, and when the body rots, that’s all she wrote. Mental states are nothing more than brain states. (Sometimes it’s called the “Mind-Brain Identity Theory”.)
- Idealism, which claims that talk of physical bodies is translatable without loss of meaning into talk of experiences. For instance, once you describe the look, smell, taste, feel, and sound of an apple, you’ve exhausted the meaning of ‘apple.’ On this model, you have actors/experiencers and experiences, none of it physical in the materialists’ sense. Death is simply transition from one sort of experience to another.
- Epiphenomenalism, a form of dualism, which recognizes the distinctiveness of mind and body, but with mind/consciousness simply along for the ride. The brain does its thing, and the mind experiences it as an act of will, an episode of worry, etc.
- Neutral monism, which says there is only one thing of which we speak, but in two different ways—using “P-predicates” for physical properties (such as the average length of the adult brain at 6.3 inches) and M-predicates (such as the feeling of satisfaction over vindication).
Of course, mind-brain dualists don’t have to sign off on Descartes’ pineal gland hypothesis. The aforementioned epiphenomenalists don’t, but neither do the occasionalists, who say that God manages all the interactions. For instance, when I decide to lift a pencil, he (on that occasion) prompts the body to lift it. And when someone jabs me with a pencil, he (on that occasion) gives rise my pain experience. That’s a lot of work for God, but he’s up to it, being omnipotent and omniscient.
Furthermore, idealists can have their own sort of mind-body dualism. For them, the experience of excruciating pain is utterly different from the experience of seeing a thumb banged by a closing car door. The former is mental, the latter physical.
And so it goes, with tweaks and reformulations and “breakthroughs” of one sort or another.
One surprising development is the emergence of “Christian physicalists.” Papers on this approach have surfaced at meetings both of the American Philosophical Association and the Evangelical Theological Society. Pardon my skepticism, but the phenomenon is reflective of the difficulty involved in doing everything justice, in “saving the appearances,” as they used to say for making sure that no phenomena were left hanging out there; and in wielding Ockham’s Razor (so as to not “multiply things beyond necessity”).