Ken Ham and Evidence

A couple weeks ago Bill Nye and Ken Ham had a debate about creationism. Of course, nearly every point Ham made was factually inaccurate. But beyond having the simple facts wrong, Ham also had a fundamental misunderstanding about the nature of evidence.

This was highlighted most clearly in Ham's answer to the question "What could change your mind?". His answer was, summarized, "Nothing". Now, this answer in and of itself is a serious strike against Ham's rationality. The point of changing your mind is to make your beliefs more accurate. If you don't even admit the possibility of changing your mind, you're saying that your beliefs cannot possibly be wrong, which is, well, arrogant to say the least.

But it's worse than just that. Ham also said that the Bible makes testable predictions. Alone, that's not a bad thing, quite the opposite. But when combined with his statement that nothing could change his mind, it shows that he doesn't understand the point of predictions. The point of predictions is to provide evidence, but the thing is, that evidence can go either way.

If you make a prediction and perform a test, and the results of the test match the prediction, then that is evidence that supports your beliefs. On the other hand, if you make a prediction, and perform a test, and the results don't match the prediction, then that is evidence that opposes your beliefs. If there is no such outcome that would go against your prediction, then it's not a prediction at all.

For example, suppose I held a rock, and based on my beliefs about the material it's made of, and the laws of physics, I predicted that when I let it go, it would fall down. Then, if I dropped it, and it fell down, that would be evidence in support of my beliefs. But, if I dropped it, and it didn't fall down, either falling up, or hovering in place, or anything else, that would be evidence opposing my beliefs. If I had predicted that when I let it go, either it would fall down, or it wouldn't, then I haven't actually made a prediction. I haven't, in any way, specified what the result of a test would be, which means no outcome can oppose my beliefs, but no outcome can support them either.

If Ham thinks the Bible really does make predictions, then those predictions failing to come true should change his mind. If nothing could change his mind, then his predictions can't actually provide evidence.

Inferential Distance

Suppose you're trying to teach someone calculus. Before they can learn calculus, they have to learn algebra. Before they can learn algebra, they have to learn arithmetic. This is the basic idea of inferential distance - background knowledge needed the understand the matter at hand.

Put this way, it looks simple, maybe not even worth talking about. But it's more subtle than that. To start with, arithmetic, algebra and calculus aren't single subjects. They're a whole bunch of related but still different subjects, which need to be learned independently. The learn integration, you have to learn differentiation, before that you have to learn limits, before that functions, variables, division, mulitplication, subtraction, addition... And don't forget the really fundamental things like what a number is.

And that's the really tricky part of inferential distance. There are a lot of things you know that you don't know you know. That is to say, you know them so well, it doesn't even occur to you to that someone else might not know it. Things that are so fundamental to your point of view that they're invisible to it. And so when you try to explain something to someone, you accidentally skip over a bunch of inferential steps, resulting in misunderstanding and each party will walk away thinking the other is stupid or crazy.

Consider a biologist talking to a creationist. They might try to explain the evidence for evolution, but before the creationist can understand that, they have to understand what evidence means, how science works, maybe even something as simple as why truth is important...

Tautologies and Rhetoric

Today, I read PZ Myers's response to this argument against evolution. PZ does a fine job of taking it down, but there is one point I'd like to make, and this is something that shows up in many places. Egnor says that evolution is a tautology and is therefore false or fallacious. The problem is that a tautology is not a fallacy. In fact, by definition, a tautology is always true.

That's what a tautology is. Something that's always true, no matter what. For example, if x is true, then x is true. That statement is always true whether or not x is. It's just not interesting. There's no real claim or anything there. A tautology is only interesting when it gets combined with something else, which is what Darwin did with evolution by combining the tautology of "survivors survive" with variation and heritability.

And of course that doesn't mean that tautologies can't be used fallaciously. They're frequently used to sneak in a fallacy such as begging the question. But pointing out a tautology doesn't in and of itself show an argument to be fallacious.