There’s a YouTube video in which Deutsch explains the famous quantum double-slit experiment, which is about particle-wave duality. Is light a particle or a wave? You pass it through a slit and, depending on whether there’s an observer and interference or not, it ends up in a wave pattern or as individual photons. More

Does probability actually exist in the physical universe, or is it a function of our ignorance? If I’m rolling a die, I don’t know which way it’s going to land; so therefore I put in a probability. But does that mean there’s an actual probabilistic unknowable thing in the universe? Is the universe rolling a die somewhere, or is it always deterministic? All probability is actually subjective. More

The overwhelming majority of theorems in mathematics are theorems that we cannot possibly prove. This is Godel’s theorem, and it also comes out of Turing’s proof of what is and is not computable. The things that are not computable vastly outnumber the things that are computable, and what is computable depends entirely upon what computers we can make in this physical universe. More

There goes my solution for Zeno’s paradox, which says before you can get all the way somewhere, you have to get halfway there. And before you can get halfway there, you have to get a quarter of the way there, and therefore, you’ll never get there. One way to get past that is to say even a series of infinite things can have a finite sum. More

You said that we went from atoms in the time of Democrates, down to nuclei, and from there to protons and neutrons, and then to quarks. It’s particles all the way down, to paraphrase Feynman. We can keep going forever. But it’s not quite forever, right? At some point you run into the Planck length. More

All knowledge is conjectural. It’s always being guessed. It’s our best understanding at any given time. You’re right to say that the axioms might be incorrect. How do we know that an axiom is incorrect? Traditionally the answer has been, “Because it’s clearly and obviously the case.” How can you prove that x plus zero must equal x?  You just have to accept that it’s true. More

If I compare math to physics: We have this domain called particle physics, and the deepest theory we have in particle physics is called the standard model. This describes all of the fundamental particles that exist and the interactions between them, the forces that exist between them, and the gauge bosons, which mediate the force between particles like electrons, protons and neutrons. More

There are two other scientific thinkers who I like who come to similar conclusions as Deutsch.  One is Nassim Taleb, who popularized the idea of the black swan, which is that no number of white swans disproves the existence of a black swan. You can never conclusively say all swans are white. More

Eddington’s experiment is an excellent example of what’s called a crucial test, which is sort of the pinnacle of what science is all about. If we do a test and it doesn’t agree with a particular theory that we have, that’s problematic. But that doesn’t mean that it refutes the theory. More

Brett, would you say that a scientific theory is a subset of a good explanation? Yes. They’re the testable kinds of good explanations. Falsifiable theories are actually a dime a dozen. This doesn’t tell you anything about the quality of the explanation you’re being given. The example that’s used in The Fabric of Reality is the grass cure for the common cold. More