The Babel Trilogy is about consciousness: what is it, and where does it come from, and how is it possible? But that problem is bound up with another one, dualism.
The great French mathematician and philosopher Rene Descartes outlined his version of mind-body dualism in The Passions of the Soul, 1649. According to his view (or, arguably, an unfair simplification of it), the body is analogous to a mechanical device—a robot, we might say—controlled or piloted by an immaterial and immortal substance that resides within it. Descartes believed the world was made up of two fundamentally different kinds of stuff, matter and thought. (Or three, really: matter, thought, and God.) Matter is res extensa—‘extended stuff,’ or, literally, stuff that takes up space. Thinking stuff, res cogitans, has no extension in space. But we human beings are uniquely dual: physical objects that think.
The big problem for dualism seems to be this: How can we make sense of the idea that the mind/soul and matter interact? There has never been a good answer to that question, and in The Concept of Mind (published exactly three centuries after The Passions of the Soul, in 1949), English philosopher Gilbert Ryle dismissed ‘Cartesian dualism’ as the ‘ghost in the machine’ theory.
Ryle’s work ushered in an era in which few philosophers took dualism seriously; instead, various forms of physicalism or naturalism or materialism, which might collectively be called “all machine, no ghost” theories, reigned supreme. They still do, despite the fact that purely physical theories have their own deep problems.
One problem is this: some philosophers have argued that the idea of causation, as in ‘the hammer caused the damage,’ is every bit as mysterious and difficult to make sense of in materialist theories as it is in dualist ones. Evidence can only ever describe events (like hammers moving and damage appearing), not the spooky (immaterial?) causing that supposedly sits between them. If that’s right, you can’t use ‘How can thoughts cause actions, or events cause thoughts?’ as a special reason for disbelieving dualism.
But a second problem for materialist theories is more important, for our purposes. If matter is all there is, how can we make sense of the idea that mind or soul or consciousness (the reality of which we experience directly every moment of our waking lives) even exists?
The question has driven some materialist philosophers, such as Daniel Dennett, to propose in all seriousness the apparently self-contradictory view that consciousness itself is an illusion; by way of illustrating how deep the trouble is, another philosopher, Galen Strawson, has memorably described this as “the silliest view that anyone has held in the whole history of humanity.”