What is free will? By Gregory Chaitin

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In a computable universe, is there any room for free will?

In classical physics, there’s also no free will, because it’s deterministic. Although, as chaos shows, classical physics -even though deterministic- is so unstable, so sensitive to initial conditions, that in practice you can’t know the initial conditions well enough to predict the future. After four weeks, the weather isn’t predictable, not even in theory, because a butterfly flapping its wings in India could affect the weather in New York. That’s called “the butterfly effect.” Now, when you go to Quantum Physics supposedly there is room for free will, you can use Quantum randomness and say that gives you free will, but that’s not terribly useful for you: would you like to have a friend who tosses a coin to make the major decisions in his life? So it’s sort of dangerous to use randomness in order to get free will. Schopenhauer has this beautiful line and says: “you can do what you want, but you can’t want what you want”, so there’s an illusion of free will. Einstein, I think, refers to this somewhere.

Now, Stephen Wolfram has taken up the issue of free will and I think he has an important idea. A new kind of science basically says the world is deterministic and can be run on a computer, so what is free will? Well, it can be run in a computer, but most of the time -and this is the main thesis of Wolfram’s book- there are no shortcuts, that is, most of the time, the only way to see what a physical system will do is to run it. Most of the time, the only way to see what a computer program will do is to run it: that is a new statement of Turing’s result. Stephen Wolfram calls this principle “computational irreducibility.” So, even though in theory every physical system is predictable -if you had an infinitely powerful computer you ran outside our universe- in practice, the fastest way to know what it will do is to run the system itself, that is, if you want to know what will happen, do the experiment and see. So in a way what he says is there is no free will, but it looks like there’s free will because there’s no fast computation that will enable to predict what something will do, in general. So, in that case, you may think of a physical system as either random or exercising free will. He also goes on in his book and somewhere he says: the world looks like it’s random, but it could all be pseudo-randomness, and we couldn’t really tell the difference. The world could be deterministic and look like there was a lot of randomness, but it could actually be pseudo-randomness, like the digits of pi. If you don’t know them, the digits of pi look very random and Stephen Wolfram believes all the randomness in the physical world is like that. That’s certainly possible, it’s a possible world, I don’t know if it’s our world. So you can regard the work on Digital Philosophy, on Digital Physics, as theoretical physics of possible worlds, not necessarily of our world. And that may sound crazy, but string theorists, for different reasons, are doing that, they talk about the multiverse, and part of the reason is that there isn’t one string theory, there are 10 to the 500 possible string theories and they don’t know which one is our universe, they think one of them is, so talking about possible worlds has become more acceptable in theoretical physics. You may take it as a bad sign; you may say theoretical physicists are talking more like philosophers because there isn’t any convincing empirical data to suggest new theories, or maybe because theoretical physicists haven’t come up with the right new theory. That’s possible, but there are people like Max Tegmark who really have some very convincing arguments in favor of multiverses and possible worlds, actually based on astronomical data, cosmological experimental data. One of the things he said is: “the physics of our particular universe is not really intellectually interesting: it may be practically important, but it’s just our postal address in the multiverse.” You have the space of every possible universe, of every possible set of laws, and this ensemble is more interesting than any particular universe. This is one of the philosophical arguments they make; Max Tegmark has cosmological and astrophysical arguments based on actual astronomical data. I remember hearing a talk from him which got more and more convincing as he was going on: the general drift of what he was saying was: cosmology used to be a very philosophical area of theoretical physics, because there was very little data, so it was wild speculation, whereas now there’s an awful lot of data and cosmology has become a rather hard subject, because you have many models that account very precisely for the data, whereas fundamental physics, when I was a student, was very solid and cosmology wasn’t, because particle physics had a lot of data and cosmology didn’t. Now it’s the other way around: in fundamental physics you have string theory, where they talk about the landscape of all possible string theories, which some people call possible worlds, some others call it the multiverse -there are different versions of these ideas, for different reasons, which reminds me of Leibniz of course, “the best of all possible worlds”- so, in a way, theoretical physicists are talking now more like philosophers. And philosophers mostly now are against metaphysics, especially if you’re an analytic philosopher, but strangely enough, metaphysics is alive and well in theoretical physics. Also, theoretical physicists are not scared of ontology, whereas that’s not fashionable in philosophy, where what’s fashionable is epistemology. Ontology belongs with the pre-Socratics and now is considered as something we will never know, the real nature of reality. But physicists try. So ontological speculations are alive in theoretical physics, even though philosophers consider them ridiculous. That’s the fashionable view if you follow analytic philosophy, which I don’t believe in, as you can guess from these remarks.

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