Picture a man in the Montana Territory, in 1885 or so, leaving a saloon in no condition to leave a saloon. Two friends pour him onto his horse. One of them slaps its flank. He gets both hands around the saddle horn, slumps forward, and is asleep before the end of the street.
Four miles later he wakes up at his own barn door. The horse is standing there, patient, waiting to be unsaddled.
He gave it no instructions. He did not steer or watch the road, because he did not watch anything. He was cargo. The horse picked the shallow place to cross the creek. It took the long way around the washout because the short way had gone soft in the spring. It stopped once for something in the road, considered it, and went around. Had the night been younger, it would have carried him from that saloon to the next saloon with the same competence and the same lack of help.
Nobody in that town thought this was remarkable. It was what horses did.
It ran on grass. It repaired itself. The people building its replacement grade their cars on a ladder: hands off, eyes off, mind off. Our man had gone one rung higher, to consciousness off. Call it the saloon test. Can you fall asleep?
A hundred and forty years later, the most valuable car company on earth sells a product called Full Self-Driving. The full name has a word after it in parentheses. Supervised. The quarterly update to shareholders adds a footnote, in case the parentheses were too subtle: “Active driver supervision required; does not make the vehicle autonomous.”
Supervised is you. You keep your eyes on the road and your hands near the wheel, and you attend. The product requires, as a condition of use, the one thing our man in Montana did not provide.
The car will drive itself for as long as you drive it.
Some cities now have cars with nobody in them at all, and you can fall asleep in the back of one. They pass the saloon test, inside a fence, with a human somewhere they can call about the traffic cone they cannot read. The horse had a fence too. It was everywhere the horse had been. It drew the fence by walking it and kept it current by walking it again.
So after all that money and the best engineers alive, a few cities have the horse back. It works where it has been walked, with a human to ask. The car in your driveway is still sorta. Its unsupervised version is coming later. It has been coming later for years.
No one had given the horse a route. It had a barn, with oats and other horses, and the road home was simply how you got there. Wanting is a good navigation system. A rule stops where it runs out. A want improvises. The horse also refused. It balked at the bridge that felt wrong and stepped around the rider who had just fallen off it, and in each of those moments it was overruling you, and you were glad.
None of this is an argument for the horse. The horse lost, and it deserved to lose. It walked. It covered thirty miles on a good day and then wanted a day off. It ate whether or not you went anywhere, which made it a vehicle with a standing idle charge. In 1900 horses and horse-drawn vehicles killed about two hundred people in New York City, about as many as died in traffic there last year, in a city less than half the size.
And its judgment was narrow, and mostly about the horse. It was self-returning more than self-driving. It could take you home. It could not take a stranger anywhere new. Horse people have a word for an animal that wants the barn too much, barn sour, and a barn sour horse will take you home through the gate and under the low branch, because the branch is your problem. The horse shared only what would kill you both. The cliff, yes. The branch, no.
So we traded it for a machine with no opinions about the bridge, and the trade was correct. But a thing that cannot refuse you cannot cover for you, and we built a civilization of vigilance to make up the difference: licenses, lane markings, rumble strips, and the designated driver, a job the horse used to do without being asked. For most of a century the thing that carried you had nothing going on upstairs.
Now we are building the judgment back, and that century is starting to look like the interlude. The horse’s judgment was small, and it covered us only where it covered the horse. What we are building is a far larger judgment with no stake at all.
The horse refused the cliff because the horse was also going over it. Nothing we are building goes over the cliff with us. An agent that books the wrong flight is not on the plane. Software that moves the wrong money does not miss it.
I work with software agents most days, and the parentheses follow me to my desk.
Our man, back at his barn door, does not thank the horse. It would not occur to him that there was anything to thank. He fell asleep drunk on a dark road, and something that could have walked him into a ditch carried him home instead, then stood in the cold and waited.
He gets down. Drunk, he pulls the saddle. He finds the brush, and the oats, and the blanket, and he does all of it before he does anything for himself, because that is the deal. You take care of the thing that takes care of you.
The things we are building to carry us will want no oats and no blanket, and whatever waits at the bottom of the cliff does not wait for them. Someday the parentheses will come off, and we will sleep the whole way home on something that wants nothing from us at the door. I suspect I will get down anyway, in the cold, and look around for something to brush.