Learning to Doubt

Human nature is to reason in certainties. It takes training to rid yourself of that handicap. Nobel-laureate, Richard Feynman, said it best:

“I can live with doubt and uncertainty. I think it’s much more interesting than live with answers which might be wrong. I have approximate answers and different degrees of certainty about various things, but I’m not absolutely certain of anything.”

Thinking in uncertainties is unnatural. Like reading, arithmetic or operating computers, it is a learned skill, not something that comes imbued in our mental hardware. But uncertainties is all there ever is, so it is a useful skill, even if it doesn’t come installed at birth.

Most people intuitively understand that some things are uncertain. You can see the weather forecast predict a 75% chance of rain. Yet, if it doesn’t rain tomorrow, you’ll hear people say that the weather report was wrong.

The weather report wasn’t wrong, your belief was. By rounding up the probability of .75 to 1, you made the error by reasoning in certainties.

Uncertainty is the Only Correct Way to Think

Weather is a trivial example. You’ll see the same fallacious reasoning in the abundant comments on my article on atheism. I get many critical commenters saying that I’m being irrational for rejecting the idea of a god without proof.

The very nature of their comment betrays a more fundamental ignorance—those people can’t reason in uncertainties. I don’t reject anything, I simply declare that with the evidence available to me, the proposition is unlikely. I can’t put an explicit percentage like the weatherman, but I’m making the forecast that there probably isn’t a god.

What if new evidence comes to me in the future, suggesting higher intelligence? I would adjust my relative uncertainty to be more in favor of the possibility. That doesn’t make my original judgement unjustified, since I had always included the possibility of new evidence changing my original position.

Many people have a false notion of reasoning that suggests if something is uncertain, they are free to believe what they want. While you’re always free to believe anything, including falsehoods, that doesn’t mean they are justified. My claim is that uncertainties, which are weighted appropriately, are the only justifiable beliefs to have.

For many things in life, the uncertainty is so small we can ignore it. I don’t regularly consider the possibility that gravity will cease to function and I’ll float into space because the doubt is miniscule. But just because we can ignore uncertainty in practical contexts doesn’t mean we can omit it wholesale.

Texas Hold ‘Em Logic

Poker is a fantastic game to train you in this counter-intuitive way of thinking about uncertainty. Good players quickly learn that there is a difference between winning and making correct decisions. Many novice players bet incorrectly on hands will sometimes win, but that doesn’t make their decisions justified.

Being a good player means being able to reason in uncertainties. Good players also realize that this uncertainty doesn’t afford them the luxury of being able to decide to believe whatever they want to. Ultimately, a 50% chance of winning a particular hand just that—50%. Believing anything other than this uncertainty is wrong.

Realizing that uncertainty exists encourages players to think not just which decisions paid off, but which decisions were valid strategies from the available evidence. Few other activities will train you in the difference between a valid argument with a false conclusion and an invalid argument with a true conclusion than poker.

Degrees of Belief

I like the poker example because it shows why thinking in uncertainties is useful. If you can’t think in uncertainties, you’ll lose a lot of money playing poker. Similarly, failing to think in uncertainties means you’ll almost certainly make bad decisions in your life.

The challenge is that uncertainties are rarely calculable like they are in games of chance. This is why I think in terms of qualitative degrees of certainty, rather than trying to pin down beliefs to 1%, 50% or 99%.

For example, if I get gossip about a friend which has been buffered through many sources, I put hazy certainty on that knowledge. Is it 75%? 60%? 50/50? Who knows? But it’s mentally labelled with an ambiguous quality.

What if I read a single scientific study about a phenomenon in psychology? Again, the exact percentage of uncertainty is probably too difficult to calculate, but I can put it as being more reasonable than speculation, but less certain than a truth confirmed repeatedly.

I try to apply the same metrics of uncertainty to my own pet theories and ideas. Holistic learning is popular here and there have been scientific studies which suggest it may be right. But I’m not under the misconception that a reasonable hypothesis is equivalent to a theory which has been rigorously tested.

Knowing something to the confidence that you can safely ignore uncertainty is extremely difficult, perhaps impossible for many domains of knowledge. It’s the ability to make use of the abundant circumstantial evidence and reasonable hypotheses which allows us to function, but at the same time realize that they don’t amount to unquestionable proof.

What About Healthy Delusions?

Am I contradicting myself from last week, where I suggested that some delusions (believing things which aren’t justified) is useful? It’s a finer point, but because it might confuse, I’ll try to clarify.

Some beliefs are useful but unjustified. Overconfidence with women is a possible example. Even if I have no evidence to show I’m the most desirable candidate, consuming myself in an irrational belief of confidence may improve my success.

There’s two ways these instrumentally rational beliefs fit into the uncertainty scheme I’ve presented. First, if I “irrationally” believe I’m good with women, and that makes me good with women, then the belief was actually justified. Such self-fulfilling prophecies may be cases of apparent irrationality which aren’t.

Perhaps thinking I’m Casanova makes me better with women, but not to the degree I believe it. In this sense, the instrumentally rational belief is useful, but technically unjustified. This is an example of a healthy delusion where it might be beneficial to believe a lie. That doesn’t make the lie true, or that unjustified beliefs suddenly become justified, simply that some degree of self-delusion may be advantageous.

Uncertainties are the only valid way of reasoning, in that they maximize true beliefs. However, there may be exceptions where maximizing true beliefs conflicts with other goals.

The Inescapability of Doubt

Once you accept that certainty is just a useful simplification, and that uncertainties are the only correct way to reason about things, life becomes much easier. Doubts, fears and worries still exist, but they stop being unnatural entities that need to be avoided, but qualities of reality that should be embraced.

Instead of avoiding doubt, learn the skills to work within it. There are many good algorithms for making smart decisions, given uncertain situations. Familiarity defeats fear. If you get in the habits of reasoning with uncertainties, doubt becomes a tool, not just an anxiety.


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