Good Explanations Are Hard to Vary

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. If someone comes along to you and says, "If you eat 1.0 kilograms of grass, it will cure your common cold," they have a testable theory. The problem is that no one should test it. Why? Because they haven't given you an explanation as to what the mechanism is that would enable grass to cure the common cold.

If you do eat the 1.0 kilograms of grass and it doesn't cure your cold, they can turn around and say, "1.1 kilograms might do it," right? Or you need a different kind of grass, or you need to always do it on a different day. It's always testable, but you're not getting anywhere; you're not making any progress.

So, I think the second piece of a good explanation is hard to vary. It has to be very precise, and there must be a good reason for the precision. The famous example he used in "The Beginning of Infinity" is, "Why do we have seasons on the Earth?" There was the old Greek explanation: "Well, it's driven by Persephone, the goddess of spring. That's when she can leave Hades," and there's this whole theory involving gods and goddesses. Not only was that not easily testable, it was very easy to vary. Persephone could have been Nike, and Hades could have been Jupiter or Zeus.

It's very easy to vary that explanation without the predictions changing. Whereas if you look at the axis tilt theory of saying "The Earth is angled at 23 degrees relative to the sun," and therefore would expect the sun to rise here in the winter and over there in the summer, the facts on that are very hard to vary. It makes risky and narrow predictions. They can predict the exact length of summer and winter at different latitudes, and you can test that very precisely.

So beyond it being a creative theory that is testable and falsifiable, it should be hard to vary the pieces of that theory without essentially destroying that theory. You certainly don't want to vary it after the fact, like your grass example: "Oh, it was one kilogram, now it's 1.1, now it's 1.2."

Finally, the predictions that it makes should be very narrow and precise, and they should be risky. For example, I believe in relativity; was it Eddington who did the experiment and showed that starlight gets bent around the eclipse? That was a prediction that Einstein had made in relativity, which turned out to be true. That was a risky prediction that took a long time to confirm.