Measured Against Reality

Friday, August 17, 2007

The Scale of Certainty

To me, certainty is relative. For example, I'm pretty damn certain that the theory of evolution explains how life has come to its present form (but not how it started, that's beyond its scope), and that information can't move faster than light (along with a host of others). Even though I think it's highly unlikely that either of those things will be shown to be false, it's still possible. The reason is that they're scientific theories, and scientific theories are always open to revision. No matter how well-established they are, no matter how much of our understanding of the world would have to be overhauled, they can still be wrong.

However, it's unlikely. The more predictions have been satisfied, the more precisely the theory works, the more confirming evidence, the less likely it is that they will be overthrown. For example, evolution has been spectacularly confirmed in thousands of cases, and there is no scientific reason to doubt its correctness. The same is true of the speed of light; it has been verified over and over to such precision and is so firmly ingrained in all of modern physics that it's not likely to be overthrown.

If I were to have a scale of certainty, things that I'm pretty sure are false on end and things that I'm pretty sure are true on the other, evolution and the unbreakability speed of light would be really close to the true end.

But what about other things? Let's take another contentious example: global warming. Right now the fact that the earth is getting warmer is close to the true end, and not far behind it is the hypothesis that it's largely anthropogenic. Other things, like that catastrophes that are predicted if we don't do anything, are a bit further back (my rationale for that is that I'm always skeptical of predictions for the future, especially ones with such poor confidence ratings (the ones I've seen are ~50-80%)).

For another fun example, the god hypothesis (by which I mean any god) is far to the false side. Other things over there are bigfoot, alien abduction, ghosts, homeopathy, and other woo.

What about the middle? What are things that I don't declare certainty about? Slightly to the truth side of the middle are my own memories. If all my readers take nothing else away from this post, take this: your memories aren't certain in any meaningful way. To take a simple (but telling) example, one of my good friends from high school is still convinced that I was in his Freshman Social Studies class. We had the same teacher but different periods, and this has been confirmed by everyone we knew in the class, including the teacher. Yet he still thinks that we were in the class together.

Memories are one of the things that people are most certain about. But they shouldn't be. It's been shown time and time again that they're malleable, and that the mere act of remember changes the memory. The more you access it, the more you change it. And memories can be falsely planted then totally internalized. It's practically a guarantee that some of your most cherished memories are either partially or totally false.

Don't believe me? Check out Mistakes Were Made (But Not by Me): Why We Justify Foolish Beliefs, Bad Decisions, and Hurtful Acts by Carol Tavris and Elliot Aronson. Besides being an all-around fantastic book, it contains an enlightening overview of the empirical support for the assertion that memory isn't trustworthy. So please, don't place more merit in your memories than they deserve.

I think that the idea of a scale of certainty is a useful one. All too often we hear people say that they're certain about things that belong in the middle of the scale, things that deserve at most a close review with verifiable evidence before a decision is made on their merit. I'm not advocating Solipsism or some kind of "we can't trust anything!" philosophy, just more careful scrutiny of how certain we are of the things in our lives. Misplaced certainty can be a disaster, and a healthy skepticism about the world (including your own memories) can never hurt.

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