There Can Be No Final Theory of Gravity

In almost all cases, you only ever have one theory on offer. In the case of gravity, there literally is only one theory on offer at the moment: there's general relativity. Previously, we did have two theories; we had Newtonian gravity, and we had general relativity. But we did a crucial experiment. This idea of a crucial experiment is the cherry on top of science.

You've got these two competing theories, and you have a particular experiment that if it goes one way, one theory is ruled out, but the other theory is not, in which case you keep that theory for so long as no problems arise. This vision of knowledge enables us to have an open-ended quest for progress, which is completely unlike any other idea about knowledge. The overwhelming majority of physicists are still Bayesian.

The reason they're still Bayesian is because this is typically what's taught in universities, and this is what passes for an intellectually rigorous way of understanding the world. But all it is, is what I would call a species of scientism. It's because they have a formula behind them: Bayes' theorem, which is a perfectly acceptable statistical formula. People use it all the time in perfectly legitimate ways. It's just that it's not an epistemology; it's not a way of guaranteeing or even being confident that your theory is actually true.

My favorite example of this is prior to 1919. Approximately every single experiment that was done on Newton's theory of gravity showed that it was consistent with Newton's theory of gravity. What does a Bayesian say in that situation? What a Bayesian has to say is getting more and more confident in Newton's theory. How does that make sense? How do you square that circle? The day before it was shown to be false was the day when you were most confident in it.

Now, Papyrion doesn't have this problem. Peperion just says at no point was Newton's theory actually true. It contains some truth, but that truth isn't a thing that we can measure. I say it contains some truth because it's certainly got more direct connection to reality than some other random person's guess about what the nature of gravity is. Gravity does indeed approximately vary as the inverse square law, but not exactly, and so we need general relativity to correct the errors in Newton's theory of gravity.

Even though general relativity is our best theory right now, it can't ultimately be the final theory of gravity. There can be no final theory of gravity. All we have is better and better approximations to reality. I think the reason we fall into Bayesianism so easily is probably related to why we found the pessimism so easily. We're evolutionarily hardwired for Bayesianism.

Every other animal on the planet that can't form good explanations is a Bayesian. They're just looking at repeated events and saying, "The sun rose yesterday; the sun will rise tomorrow." If I touch that thing, it's hot; it's probably going to be hot in the future. So that is how most of our biological systems and how most of our evolutionary heritage worked.

It's just now we have this neocortex that can form good explanations, that can explain the seen in terms of the unseen, and that gives us a higher level of reasoning. But that higher level of reasoning is not instinctual to us. It requires effort; it requires deep thinking. But we default to Bayesianism because that is how a lot of the natural world around us seems to work, at least at the purely biological level.