Years ago, I was at my aunt and uncle’s house, and my little cousins were playing with the hose in the back yard, digging up some grass and making the water pool up. I was supposed to keep an eye on them, but I didn’t stop them from inflicting minor damage on the lawn.

I remembered doing the same thing with the hose and the yard when I was a little kid. I imagined I was making a river, and I would have this mental image—daydream, enchantment, whatever you want to call it—that somehow enlivened the actual thing I was doing. To them they’re making a river, I though; I don’t want to stop them. (My aunt and uncle saw it differently. It was their yard, after all.)...