The Watchmaker: my fav argument

[Belacqua]

I get the feeling you've misled us.

No, what he's saying about falsifiability is exactly right.

In the philosophy of science, falsifiability or refutability is the capacity for a statement, theory or hypothesis to be contradicted by evidence. For example, the statement "All swans are white" is falsifiable because one can observe that black swans exist.

That's right.

In the example John gave of the lights and the fairies, both types of evidence (the lights being on or the lights being off) point to the same conclusion according to the theory. The empirical evidence as interpreted through the theory is incapable of showing that the fairies don't exist. Therefore, the theory about the lights and the fairies can't be falsified, therefore it isn't science.

The famous example that Popper used was Freud's system. Freud wanted to make his theories scientific, but Popper showed that they weren't because they couldn't be falsified.

It's easy to see if we take a simplified caricature:

Suppose Freud says that all sons want to have sex with their mothers, but they usually resist doing so. What evidence could falsify this theory?

Imagine that one mother has two sons. One son stays in the family home all his life with his parents. The other son moves to China and is never heard from again. Freud would say that the first son, staying home, proves his theory because clearly he stayed home to be close to his mother, because he wants to have sex with her, even though he never did. And clearly the son who moved to China went so far away because he wanted to have sex with his mother, but he had to resist, so he moved far away to make it impossible.

So doing X is proof of the theory, but doing the opposite of X is also proof of the theory. You can't do anything that doesn't prove the theory. Therefore it's not falsifiable. Therefore it's not science.