Theoretical physicist Sean Carroll part-times as a debater and defender for the naturalistic worldview. In recent talks, he has emphasized a point that I think only a physicist could sincerely make that as far as I know hasn't really gotten much traction: The laws of physics that govern the way matter behaves at the level of our everyday experience are fully understood. And even though there are still things within the universe that we don't know about, like dark matter and dark energy, black holes, and the origin of the universe - when those mysteries are eventually revealed to us by science they will not fundamentally change the equations that describe the everyday world. So nothing like a soul or an afterlife that has any interaction with the human body or anything made of atoms can exist because any such metaphysical substance would either be too weak to interact with the atoms or they would have already been detected. Therefore, souls, ghosts, astrology, psychokinesis, the afterlife, and almost every concept of god, except perhaps deism is ruled out.
That equation by the way is:
Is this a good overall argument? Does Carroll have a good case to be made?
Those are the questions I want to raise. I have a strong leaning towards yes, it is a good argument, but I want to examine some potential problems it might have or could have. The most obvious problem the argument could have is what if Carroll's wrong? That's always a possibility. After all, his argument is not an argument that tries to prove anything logically true. It's an argument that is a posterori, not a priori. It all depends on whether the laws of physics at our everyday experience really are known in such a way that no further physics will ever change them of their ontological implications. What if that's just not the case?
Well, then there is an opening for a believer in the things the argument attempts to falsify. But even if there is an opening, it could still be the case that any future physics that does change the equation in any way won't do so in a way that will make it any more favorable to a theist or spiritualist. It might just be more of the same kind of physics that is more favorable to naturalism. But going back to the original point, the certitude regarding our knowledge of these laws described in the equation must be high, or, to use a technical term, pretty high. It's a matter of probability that only someone with a large body of knowledge in physics and with the history of science can properly assess, and so that of course disqualifies me. I can only refer to the experts to help inform my view of the matter.
There have been many times when scientists declared physics to be done, only to be totally proven false by new discoveries. This was most famously done by Lord Kelvin, when he is said to have claimed in 1900 that "There is nothing new to be discovered in physics now; All that remains is more and more precise measurement."* This was just a few years before Special Relativity was created by Einstein which completely revolutionized physics and changed our fundamental scientific ontology. What a colossal failure. There are many similar examples. So, given that history is littered with failed scientific predictions, are there good reasons to think that is not the case with Carroll's argument?
Well, Carroll himself seems to think so. In a lecture he gave at Oxford, Poetic Naturalism, he responds to this potential problem, saying:
The difference with our current framework of quantum field theory is that if quantum field theory is correct in a certain regime - Newtonian mechanics is correct in a certain regime, right? We don't need quantum mechanics to fly rocket to the moon for example. Quantum field theory unlike Newtonian mechanics tells us very precisely what regime it is valid in. It gives us a delineation of where the theory is supposed to work and where it's not supposed to work. You can draw that line, and it turns out that in practice, drawing the line around the quantum field theory I drew on the previous slide includes all our everyday experience.
So let me explain that a little bit more ...you've probably heard about somewhere in your physics education, are things fundamentally particles or they fundamentally waves? And if you're like me when you heard that never really heard what the answer was to that question, so I'll give you the answer: it's waves. Okay that's the answer. Stuff in the universe, the fundamental ontology of reality are quantum fields and the reason why the particles come in is because the quantum part of that implies that when you look very carefully at the fields they resolve into particles. Not because they all are particles - they are fields, they are waves, they are smooth continuous things going all of space, but quantum mechanics says that what we see is not what their is.
Elsewhere, Carroll has articulated on the point:
As Michael Salem points out on an alternative social-media site (rhymes with “lacebook”), some of the resistance to this really quite unobjectionable claim comes from a lack of familiarity with the idea of a “range of validity” for a theory. We tend to think of scientific theories as “right” or “wrong,” which is hardly surprising. But not correct! Theories can be “right” within a certain regime, and useless outside that regime. Newtonian gravity is perfectly good if you want to fly a rocket to the Moon. But you need to toss it out and use general relativity (which has a wider range of validity) if you want to talk about black holes. And you have to toss out GR and use quantum gravity if you want to talk about the birth of the universe.
On another blog post he's written:
What there won’t be is some dramatic paradigm shift that says “Oops, sorry about those electrons and protons and neutrons, we found that they don’t really exist. Now it’s zylbots all the way down.” Nor will we have discovered new fundamental particles and forces that are crucial to telling the story of everyday phenomena. If those existed, we would have found them by now. The view of electrons and protons and neutrons interacting through the Standard Model and gravity will stay with us forever — added to and better understood, but never replaced or drastically modified.
So is this a slam dunk argument? Is there any possibility that a skeptic of Carroll's claim could have a chance in being right? That is one tough question for a person to calculate, especially a person not intimately familiar with the fundamental laws of physics. I'm not sure if other physicists have made Carroll's argument, but I'd like to see many more physicists weigh in. I think that for some scientists, they get so enamored with the fundamental laws of physics and their equations that they deify them and almost turn them into gods. I don't think Carroll is doing that, but I do think some physicists kind of do, like MIT physicist Max Tegmark. That's another thing to consider. Anyway, I do think Carroll's argument is a powerful one overall, and one that has the potential for being a very good scientific argument in favor of naturalism. But, it needs to be debated.
Watch Carroll's lecture here:
*There is controversy over whether Kelvin really said this.