Even when you think you’ve proved something, there’s a small chance that your proof was incorrect. Even if you remember proving it beyond all shadow of a doubt, there’s a chance that your memories are wrong. There’s a tiny chance that your logic was flawed. There’s a teeny tiny but nonzero chance that you’re literally insane, and you believe arguments that are actually invalid. There’s an even smaller chance that the universe has been lying to us to the whole time, and the very foundations of logic are about to shift.

There are simple proofs that $2 + 2 = 4$, and it looks logically intuitive. The visual proof that $••$ near $••$ is $••••$ seems irrefutable. You don’t even need visual dots on a screen: you can visualize it in your mind. You can check on a piece of paper. $2 + 2 = 4$, that feels certain.

And yet, you may wake up tomorrow and find that two plus two is three.

It’s possible that the sun will turn into a large chocolate cake tomorrow.

Don’t misunderstand me. There’s not a “quantum chance” that the sun could turn into a cake tomorrow. The sun cannot turn into a cake tomorrow according to the known laws of physics. But there’s a chance that the laws of physics are an elaborate hoax and reality’s been lying to us since the beginning.

In other words, we’ve found out a bunch of rules for how things work, and as far as we can tell they’re invariant. But that doesn’t mean that they will remain invariant.

Now, I’m not saying that you should panic. We understand the universe very well, and we’re nearly certain that the laws of physics will continue to hold tomorrow.

But we can’t prove it. Nobody can prove anything. Ever.

In fact, certainty is a very dangerous thing for a mind. It means you’re not allowed to change your mind ever, no matter what happens. Even if the skies open up and Zeus himself steps down to set you straight, you can’t become un-certain. If you’re certain of something, then you think everybody mass-hallucinating is more likely than you being wrong.

It is a common saying that science can never prove a thing true, it can only prove things false. This is mostly true. It is much easier to rule out bad ideas than it is to single out good ones: but nothing can be proved absolutely false any more than it can be proved absolutely true. Certainty is simply not attainable.

There is a tiny chance that your mind is being manipulated, and there’s a tiny chance that the universe is not how it seems. There’s a tiny chance that the lords of the cosmos are playing an intricate joke. Even though those probabilities are vanishingly small, you can never be more confident in anything than you are confident that your brain is trustworthy.

One possible reaction to this fact is to never use definitives in speech. This is a pretty silly solution, and hobbles our ability to communicate. We wouldn’t be able to say “Sally is going to the movies” any more. We’d have to say things like “Sally wants to go to the movies”, or “Sally has stated her intent to attend the movies”, and even then we run into trouble. By the time we utter “I am reasonably certain that I heard Sally state her intent to attend the movies”, we’re missing the point.

It is stupid to throw out definitives in our language. Rather, since the word “is” or the phrase “will be” cannot be certainties, we use them to express things that we, the speaker believe are true with a reasonable degree of certainty.

With that in mind, know this: Simplifience will not qualify near-certainties. I will not say “we are fairly certain that you cannot remove an axe from its handle and its blade”. I will not say “it seems very likely that gravity holds”. I will tell you how things are, to the best of humanity’s scientific knowledge.

You should already be skeptical of my claims, regardless of the confidence whith which I state them. Truth is only what reality enforces, and you must always be ready to drop any beleif at a moment’s notice, as soon as reality starts contradicting your claims.

Everything is uncertain. Nothing can be shown to be absolutely true. But some things are well established and strongly supported. Some knowledge is beautiful and simple and gives you power to steer the future. I will discuss them as facts – because facts is what they are.

But always remember that anything can be overturned, given enough evidence to the contrary.