In the nineteenth century, Laplace concluded that physical laws determined the universe:
“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.
He challenged the centuries-old dualism of Descartes, that mind controls matter, by claiming that physical laws explained everything so mind was just a “ghost in the machine” (Ryle, 1949). Apparently, science not only didn’t need religion, it was better off without it.
The case against dualism is that physical events entirely cause other physical events, so the universe is causally complete and its causal chain has no gaps. If one pushes one end of a tube of balls, a ball pops out the other end and no mind or soul is needed to make that happen. That all physical facts come from other physical facts leaves no room for non-physical causes like a mind.
But just as physical realism was dominating dualism, its own vision of a world of fixed laws that define fixed events took a crippling blow from a new kid on the block, quantum theory. Quantum mechanics asserts that no physical event is 100% certain and the evidence agrees. In the Stern-Gerlach experiment, silver atoms in a magnetic field go up or down based on a spin that is perfectly random. We can’t sort the atoms into those going up or down in advance because they are initially identical and the spin direction that moves them in a magnetic field is decided when they interact with it, not before. Quantum theory says it happens when an atom observes the field, just as where a photon hits a screen happens when it observes the screen. In a mechanical world, the physical history of an event should completely define it, but it isn’t so in our world. Quantum theory implies that every quantum entity chooses, by itself, how it physically interacts and this unpredictability is inherent to reality itself.
According to quantum theory, observing a quantum wave randomly chooses from its lawful possibilities to actualize a physical event from one option and obliterate the rest. The observation stops quantum waves expanding endlessly and causes a physical event. Quantum theory needs an observer outside the quantum system to end the quantum chain while a closed physical system has by definition nothing outside it to end the chain, so physical realism has no observer.
Figure 6.1 compares the reality options:
In Figure 6.1a, reality is one set of physical events causing the next, with no randomness and no observer, so there is no evolution and no observing “I”.
Figure 6.1b is more complex, as now two event sets in different reality realms, mental and physical, affect not only their realm but also the other, but no-one can say what mind events add to physical events or how they affect them.
In Figure 6.1c, reality is a series of observations each leading the next just as quantum theory says. Each physical event is the observed result of quantum events but doesn’t itself have any further consequences, so there are no physical causes. The physical world is an epiphenomenon that, like a train whistle, appears but doesn’t affect the engine, which in this case is quantum.
Physical events link lawfully to each other by their quantum precedents so physical laws are the resulting correlations. The quantum world creates the physical world and quantum laws create the physical laws we deduce. The quantum sequence leaves no gaps for physical causes to explain just as physical causality left no gaps for the mental causes of dualism to explain. The quantum world simply chooses a physical event and a thread of physical history is added.
Physical realism has no observer or choice but quantum realism has both because every quantum collapse is an observation choice. The observer is why quantum theory works when physical realism doesn’t.