Try to describe the route from your home to somewhere you’ve driven fifty times, turn by turn, without help. Most people under about forty find they can’t, and find it mildly embarrassing, and then decide it doesn’t matter. They’re right that it doesn’t matter. That’s what makes navigation the perfect place to start.

Here’s what happened. Route-finding used to be a skill you maintained: you built a rough map in your head, noticed landmarks, kept a sense of which way north was. Then a device did it better, instantly, and everyone stopped maintaining the skill, because maintaining a skill you never use is not a thing humans do. Within about a decade the ability quietly degraded across an entire population, and nobody misses it, and the trade was excellent. You got reliable arrival, live traffic, and the end of a genuinely stupid category of argument in the car.

We’ve made this trade many times and it’s usually been good. Nobody remembers phone numbers now. Mental arithmetic has softened since calculators. Spelling has softened since autocorrect, and if you want the oldest example, writing itself was attacked when it arrived on the grounds that it would destroy people’s memories. It did destroy people’s memories. Ancient audiences could hold poems that would take us months, and we gave that up, and in exchange we got libraries and got to keep the poems anyway. Almost every offloading trade in history has come out in our favor, and anyone who tells you otherwise is selling nostalgia.

So why is this round different? Three properties, and it’s worth being precise instead of gloomy.

The first is breadth. Every previous offload was narrow. A calculator takes arithmetic and touches nothing else. What’s being offloaded now isn’t a skill, it’s a stage: the part where you sit with something ambiguous, hold the pieces in your head, and work out what you think. That stage is upstream of everything else you do, so the atrophy doesn’t stay in one place.

The second is that the fallback disappears. When your phone dies you can still get home, badly, by asking someone and reading signs, because the world is still full of the redundant information navigation used to run on. The equivalent fallback for judgment is other people’s judgment, which is exactly what’s degrading at the same time, in the same way, for the same reason.

The third is the one this stretch of the series keeps arriving at. You can’t supervise a skill you no longer have. Being lost is cheap: the machine is wrong about the road, you notice within ten minutes, and the cost is ten minutes. The machine being wrong about a diagnosis, a contract, or a design decision is caught by a person who could have done the work themselves, and only by that person. Yesterday’s post was about a man clicking approve at 1.7 seconds. The version of that problem in this post is worse, because his problem was time and this one is capacity.

I should be honest that the evidence here is thinner than the argument. Navigation atrophy is reasonably well established. Whether the same happens to reasoning, at what rate, and whether it reverses when people go back to unaided work, nobody knows, because the experiment started five minutes ago and there’s no control group. It’s also possible the offloading frees people to think at a higher level, the way nobody laments that engineers don’t compute logarithms by hand, and it might turn out that the general skill of directing and checking machine work is the real skill and we’re all clumsily learning it. I hold that possibility genuinely. What I notice is that it’s the same optimistic sentence from yesterday’s post about apprenticeship, which means both hopes are leaning on one plank.

There’s also a difference between the trades worth making and the ones worth refusing, and I don’t think the answer is to do everything the hard way. Nobody should be proud of doing arithmetic by hand. The distinction I’d draw is between offloading a step and offloading the whole judgment: use the machine to gather, draft, and check, keep for yourself the part where you decide what you actually think. That line is easy to state and slippery to hold, especially at eleven at night when the draft is good enough.

Tonight’s exercise. Take one thing you now routinely hand to a machine and do it unaided, once, this week. Write the difficult message yourself. Work out the number yourself. Plan the route in your head before you look. Notice two things: how much harder it is than you expected, and how much of that difficulty is the skill being rusty rather than the task being hard. That gap is the measurement. It’s the only one you’ll get, and it’s only available while you can still remember what the skill felt like.