# It’s Rare to Have Competing, Viable, Scientific Theories

**General relativity vs. Newtonian mechanics is a recent example**

**Naval: **There’s also Solomonoff’s theory of induction. I don’t know if you’ve looked at that at all?

**Brett: **I’ve heard of it, but I haven’t investigated it.

**Naval: **I’m going to mangle the description. It says that if you want to find a new theory that explains why something is happening—in this case something that’s encoded as a binary string—then the correct one is a probability-weighted theory that takes into account all possible theories and weighs them based on their complexity. The simpler theories are more likely to be true, and the more complex ones are less likely to be true. You sum them all together, and that’s how you figure out the correct probability distribution function for your explanation.

**Brett: **That’s similar to Bayesianism, isn’t it? In both cases they’re assuming you can enumerate all the possible theories. But it’s very rare in science to have more than one viable theory. There was the Newtonian theory of gravity and the theory of general relativity. That’s one of the rare occasions where you had two competing theories. It’s almost unknown to have three competing theories to try and weigh.

**Naval: **What confuses people is that induction and Bayesianism work well for finite, constrained spaces that are already known. They’re not good for new explanations.

Bayesianism says, “I got new information and used it to weigh the previous probability predictions that I had. Now I’ve changed my probability based (Read more...)