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By Root 692 0

course, we don’t have to imagine this. The brain is such a machine. It was made by Mother Nature through natural selection, a process no different in kind from the trial-and-error tinkering of a slow and dim-witted inventor with endless time and lots of resources. Here Leibniz introduces an idea that science-fiction writers have been employing off and on since he invented it: “We can conceive of the brain’s being enlarged while maintaining the same relative proportions among its parts, so that we could walk into it as we can walk into a mill.” Or alternatively, as Isaac Asimov supposed in Fantastic Voyage, we can shrink ourselves to a size that would enable us to walk around the fantastically complicated machine that is a human brain.

Leibniz wrote: “Suppose we do walk into it; all we would find there are cogs and levers and so on pushing one another, and never anything to account for a perception.” Or, updating a bit, all we would ever find are sodium and potassium molecules moving one way or the other, complex neurotransmitter molecules changing molecular shape as other molecules come into contact with them. We would never find anything that introspection identifies as an experience, a sensation, a feeling, even a thought about stuff. We would never find anything that reveals what it’s like to have a sensation of yellow, an experience of pain, a smell or sound, or any other experience.

Leibniz’s thought experiment leads straight to Nagel’s conclusion—that it’s inconceivable that matter in motion, regardless of how complicated, could turn out to be experiences with qualitative feels to them, like colors, sounds, pains, smells, touches. But Leibniz took matters one step further. He concluded, “Perception must be sought in simple substances, not in composite things like machines.” A simple substance is one with no pieces, no moving parts, no components. It can’t be broken down into whatever might turn out to be the basic building blocks of physical reality, what we now think to be fermions and bosons. And if the mind is what has perceptions, then it has to be one of these simple nonphysical substances. Scientism refuted, QED.

How should scientism respond to such an argument? Well, we know that there are no spiritual substances—simple or complex. One or more of the premises of Leibniz’s argument must be wrong. And we know we can’t rely on introspection to check on any of the premises of his argument. Nor can we give weight to introspection’s feeling that there will still be something left to explain—what it’s like to have experiences—once we understand completely how the brain works. So, when it comes to the persistent question of what the mind is, scientism can disregard objections that are based on Leibniz’s thought experiment or Nagel’s. It can disregard the argument that subjectivity is not physical, so there must be a nonphysical mind, person, self, soul that has the subjective experience. It can disregard denials that the mind is the brain.

Is this intellectually responsible? Yes. Our evidence for the truth of physics as the complete theory of reality is much stronger than our evidence for the truth of the conclusion of any thought experiment that relies on introspection. Plus, introspection is wrong about so much, it can’t carry any weight against science. Scientism is safe to conclude that there are flaws in Nagel’s argument and Leibniz’s. We don’t know where the slips occur. But we know that their conclusions are false.

To repeat, it would be intellectually irresponsible for neuroscience to disregard these arguments. They present in a wonderfully effective way some of the great scientific challenges that face neuroscience. It’s a challenge scientistic non-neuroscientists are confident neuroscience will eventually resolve. The challenges of neuroscience are not problems for scientism.

FREE WILL? ARE YOU KIDDING?

Even before it gets around to denying that there is a self, a soul, or a person to have free will, science has already disposed of the possibility that it might have any. The denial that there is any