In 1637, Descartes concluded that mind is real because a thinker can doubt what he sees but not that he sees, so our sensory experiences could be a dream but the experience of them is real. The physicalism of science (Figure 6.1) then required a mind reality to consciously experience it (Figure 6.2). In this Dualism-A, mind and matter exist in different realms that interact, to provide both the machine of science and the immaterial observer of religion.
This view held for centuries until in 1814, Laplace argued that physical causes alone sufficed:
“We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.” Laplace, in (Truscott & Emory, 1951), p4.
In this causal determinism, science not only doesn’t need religion, but is better off without it, because the physical world is causally closed. It is a causal chain with no gaps, like a tube of balls where pushing one end makes a ball pop out the other end, with no mind needed to make it happen. If physical events follow a predetermined path, there is no room for mental causes.
Dualism couldn’t counter this because it can’t explain how mind affects matter (1.2.2), and logic confirms that causal closure means that if the mind has a physical cause, it must also be physical and so not mind, and if not, it has no physical effect (Kim, 1999). Physicalism doesn’t let the mind affect the body as we think, so Dualism-B, that mind exists but does nothing, is essentially physicalism.
Supporters of mental causation then sought to demonstrate it by paranormal events like telekinesis (mentally moving objects), or extra-sensory perception (seeing what is physically unseeable), but these results haven’t replicated reliably (Kelly at al., 2007).
Then just as physicalism was destroying the foundations of dualism, quantum theory destroyed its foundations, by stating that no physical event is 100% certain. For example, in the Stern-Gerlach experiment, silver atoms fired into a magnetic field move up or down based on a perfectly random spin that is set when they enter the field. We can’t pre-sort the atoms into those that will go up or down as they are initially identical, and according to quantum theory, the spin that decides their movement is defined when they enter the field, not before. In a causally closed universe, the physical past causes the physical future, but in our universe it doesn’t, and physicalism can’t explain this.
Physicalism then can’t explain the experiential fact of consciousness or the physical facts, and dualism can’t explain how an immaterial observer can exist alongside a material world, but this didn’t stop its supporters from proposing causes that derive from matter.