Here's an excerpt from Sabine Hossenfelder's book, Existential Physics, that I liked a lot. In another post I'll share some subtleties about her emphasis on reductionism as being how the universe works.
Does it take anything more than particles to make a conscious being?
I have found that many people reflexively reject the possibility that human consciousness arises from interactions of the many particles in their brain. They seem wedded to the idea that somehow something must be different about consciousness.
And while the scientifically minded among them do not call it a soul, it is what they mean. They are looking for the mysterious, the unexplainable, the Extra that would make their existence special.
They find it inconceivable that their precious thoughts are "merely" consequences of a lot of particles doing whatever the laws of nature dictate. Certainly, they insist, consciousness must be more than this.
In a 2019 survey, 75.8 percent of Americans subscribed to this idea of dualism -- that the human mind is more than a complicated biological machine. In Singapore, the percentage of dualists was even higher: 88.3 percent.
If you are among the dualist majority, we have to make a deal before we can move on. You put aside your belief that consciousness requires some Extra that physics doesn't account for and hear what I have to say.
In return, I promise that if you, at the end of this book, still insist the human brain is exempt from the laws of nature, I'll let you get away with it.
Having said that, as a particle physicist by training, I have to inform you that the whole is the sum of the parts, not more and not less. Countless experiments have confirmed for millennia that things are made of smaller things, and if you know what the small things do, then you can tell what the large things do.
There is not a single known exception to this rule. There is not even a consistent theory for such an exception.
Just as a country's history is a consequence of the behavior of its citizens and their interactions with the environment, so is the behavior of the citizens a consequence of the properties and interactions of the particles they are made of.
Both are hypotheses that have withstood any test they have been subjected to -- so far. As a scientist, I therefore accept them. I accept them not as ultimate truths, for they may one day be revised, but as best current knowledge.
A lot of people seem to think it is merely a philosophical stance that the behavior of a composite object (for example, you) is determined by the behavior of its constituents -- that is, subatomic particles. They call it reductionism or materialism or, sometimes, physicalism, as if giving it a name that ends in -ism will somehow make it disappear.
But reductionism -- according to which the behavior of an object can be deduced from ("reduced to," as the philosophers would say) the properties, behavior, and interactions of the object's constituents -- is not a philosophy. It's one of the best established facts about nature.
Nevertheless, I am not a reductionist hard-liner. Our knowledge about the laws of nature is limited, much remains to be understood, and reductionism may fail in subtle ways I will discuss later. However, you have to learn the rules before you can break them.
And in science, our rules are based on facts. Fact is, we have never observed an object of many particles whose behavior falsified reductionism, though this could have happened countless times.
We have never seen a molecule that didn't have the properties you'd expect, given what we know about the atoms it is made of. We have never encountered a drug that caused effects that its molecular composition would have ruled out. We have never produced a material whose behavior was in conflict with the physics of elementary particles.
If you say "holism," I hear "bullshit."
We certainly know of many things that we cannot currently predict, for our mathematical skills and computational tools are limited. The average human brain, for example, contains about a thousand trillion trillion atoms.
Even with today's most powerful supercomputers, no one can calculate just how all these atoms interact to create conscious thought. But we also have no reason to think it is not possible. For all we currently know, if we had a big enough computer, nothing would prevent us from simulating a brain atom by atom.
In contrast, assuming that composite systems -- brains, society, the universe as a whole -- display any kind of behavior that does not derive from the behavior of their constituents is unnecessary. No evidence calls for it.
It is as unnecessary as the hypothesis of God. Not wrong, but ascientific.