This is probably the edgiest post I will ever write, because I want to talk today about edge cases. Like some of the concepts I described in my post on narrative physics, this is another instance of me taking an idea from a “hard” field (science, engineering, math) and applying it to a “soft” field (political science, philosophy, literature), and this time that concept is edge cases. If you’re not familiar, an edge case is an engineering term used in testing to express failure modes. For a product to be deemed effective/safe/useful, it has to be rigorously tested, and not just under “normal” conditions; it has to be exposed to the most extreme and unusual conditions that the engineers can possibly imagine it might ever conceivably experience, and tested in that environment, too. Those extreme and unusual conditions are known as edge cases, and it is very common for a product to require redesign after it has met its nominal operating conditions because it fails to account for edge cases. If only that concept were applied outside of engineering.

Take a satellite. Although we can predict with some accuracy that, under nominal conditions, exactly what conditions a satellite will experience, we still test it far beyond those expected conditions to account for the worst conditions we expect the spacecraft could encounter. We write the software to have fail-safe mechanisms, like watchdog timers, so that even if something goes terribly wrong that we never expected, the satellite will still be able to recover. While we can’t account for every extreme, we do account for many of them, and that’s why many of our satellites last far beyond their intended lifespans. The Spirit and Opportunity Mars rovers, for instance, had a 90 day expected mission. How long did they last? Spirit lasted for six years. Opportunity lasted for fifteen years. This after being launched atop a barely controlled explosion into space, traveling about 165 million miles through space, then dropping to the surface of an alien world in a giant beach ball to bounce to a stop (see picture below if you don’t believe me – we really landed rovers on Mars by wrapping them in a giant beach ball and bouncing them down to the surface). That’s the power of accounting for edge cases.

Knowing the power of edge cases, I was rather surprised to find that very few non-technical fields leveraged such a useful concept. Philosophy, for instance, has a tendency to disregard them. Kant accounted for them with his idea that something is right only insofar as you should desire that it should become universal law, but most other philosophers barely even tried. Utilitarianism would say that they’re unnecessary, because edge cases don’t constitute the majority and therefore are unimportant, by which logic we should stop crash-testing cars, because they spend the majority of their time driving, not crashing. But where I really think edge cases would be a powerful tool is in policy. Don’t worry, I’m not going to talk about specific policies or get into politics. I will observe merely that it often seems that policies (at any level – national, corporate, local, even the local crossword society) forget to account for the edge cases. They’ll cover a majority, and they’ll address some of the outliers, but they will inevitably neglect to account for all of the edge cases. And I’ll leave it at that, because this isn’t a website about politics.

Edge cases feature in literature, too, but a little differently. In a lot of ways, telling a story is about finding the edge cases in a given scenario, because the edge cases are the interesting stories to tell. When someone like Brandon Sanderson talks about making a magic system and then looking for ways to break it, he’s essentially talking about edge cases. When you sit down and do your world-building, the most interesting features of the world might come from the edge cases. For instance, maybe you decide to make your planet tidally locked, or even make a toroidal planet, or a contact binary. The best stories feature the extremes of environment and of the human experience, and it is about those that edge cases are intended to help you think.

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