Doggerel #6: “Impossible”

Welcome back to “Doggerel,” where I discuss words and phrases that are misused, abused, or just plain meaningless.

To me, “impossible” isn’t really a word for skeptics, despite what you may have heard. It’s only really supposed to be used for some relatively narrow circumstances. Even when it’s used, there’s typically an understanding that it’s conditional or just very unlikely. Let’s look at those extremes:

  • Logically impossible: This version of the word refers to things that involve a contradiction in their definition, like “five-sided square.” Squares have four sides by definition, which contradicts the part about being five-sided.
  • Mathematically impossible: Some things just can’t be done in pure mathematics. For example, you can’t “square the circle” in a finite number of steps. Mathematicians can say it’s impossible because they know the rules they’re working under. If a process asks for you to use only a straight edge and collapsing compass, you can’t “discover” that you can use a ruler.

These are the only things that come to mind when I think about what’s genuinely impossible. When you leave the comparatively ethereal realms of semantics and pure mathematics, things get messy. In the real world, we don’t know the rules in advance. We don’t know what all the entities are. We can be mistaken about rules that once seemed iron-clad. We can incorrectly define entities, forcing us to change the definition to conform with newly discovered properties. We live in an uncertain world. Even if we did figure it all out, I doubt we’d really know if we figured it all out. Because of that uncertainty, there’s good reason to avoid absolute statements.

When a skeptic says a perpetual motion machine is impossible, it’s generally understood by other skeptics that he means it’s impossible if the laws of thermodynamics are true. It’s a conditional, not an absolute. Thermodynamics is one of the best established theories in science. It’s one of the foundations behind nearly everything we engineer. But in science, all theories are tentative. Someone might just find a loophole someday, invent a free energy machine, and we might have to eat humble pie. (It’ll be delicious.) The uncertainty of the universe is the reason why ideas generally can’t be dismissed as impossible, just very unlikely.

Quite the opposite of familiar tropes, I tend to see “impossible” inserted between the lines of various extraordinary claims. People who believe in supernatural phenomena are often quick to dismiss more mundane explanations out of hand. They often seem to assume that if they can’t imagine a mundane explanation, then all mundane explanations are impossible before they even bother discussing the topic. They may not use the actual word, favoring subtext, but it stands out quite a lot to people like me. They may not even realize they’re saying it.

Advice to my opponents: “Impossible,” taken literally, is usually a very bold claim. Don’t use it lightly, and interpret other people’s use of it charitably. “Highly unlikely” is generally preferable. If you’re asserting something is literally impossible, let everyone know that you mean it.


One response to “Doggerel #6: “Impossible”

  1. Pingback: The Doggerel Index | The Bronze Blog

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