There’s a proposition that if you’re rational, the future evolution of your beliefs is unpredictable to you.
This is relevant to everything, including, importantly, politics.
It’s easy to explain why it’s true:
Suppose you’re rational. Then anything that is predictable based on your current information, you have predicted. (Presumably you weren’t shocked when the sun rose this morning.) In other words, predictable events are already incorporated into your beliefs.
It follows that the only thing left to change your beliefs over time is new data that wasn’t predictable.
That immediately implies that if you’re rational, the future evolution of your beliefs over time is unpredictable to you.
(Thus the title of this post, a quote from economist and political philosopher Friedrich Hayek.)
Contrapositive: If you can predict the future evolution of your beliefs, you’re not rational.
The implications are kind of astounding.
For one thing, there’s an old notion that “social advancement” is objectively assessable, and we can predict how society’s views will evolve as society becomes more advanced. We do this by looking at the recent direction of changes in our beliefs, and inferring that in the future, they will continue to change in the same direction.
WROOOOOONG! (Insert grating buzzer sound here.)
If you’re thinking this way, you haven’t really understood your own notion of what it means to be advanced, if your notion of “advanced” involves rationality.
E.g., suppose in 1933 everyone had said, “Hey, we just repealed Prohibition! So obviously what a more advanced society than us would do, would be to go further in the same direction and FORCE everyone to drink alcohol!”
Ah, not so much, no.
While that example is fanciful, try this one:
In the past, it was illegal in some areas to wear the clothes of the opposite sex. Now we’ve gotten rid of those laws, and some seem to think a straight-line extrapolation of that change implies that the next, more advanced step is to fine businesses for calling a woman a woman. Apart from the question of whether this is really a straight-line extrapolation of anything, that’s not the way to forecast society’s more advanced beliefs anyway.
Actually, if you’re rational, the path of your beliefs through belief space will be what’s called a random walk, or, more poetically, a drunken walk. That means that for your beliefs to change in any direction is equally likely, in an expected value sense. It won’t be a continuation of their past direction (except by coincidence).
See the link above for what a random walk looks like.
It looks like chaos.
This isn’t saying reality won’t be like the past – you can expect that Earth’s gravity will be tomorrow what it is today – it’s saying your beliefs’ future trend won’t necessarily be like their recent trend. In other words, if you revised your estimate of Earth’s gravity upward today, you can’t conclude that you’re probably going to revise it upward again tomorrow.
It’s easy to see why this has to be the case. Otherwise you’d say something like this:
“I currently believe Earth’s surface gravity is 9.81 meters per second per second, but I expect to receive new information tomorrow which will make me believe that it’s 9.82 meters per second per second.” That would be fucktarded, in technical terms. Obviously if you really anticipated that, then your current belief is that it’s 9.82!
An implication: If you’re not perpetually surprised by the changes in your own beliefs over time, you’re doing something wrong intellectually.
If you’re rational, every now and then the change to your beliefs will be very large. Some propositions that seem outrageous to you today will seem indisputable to you some number of years from now.