To build a folly is essentially to do something a second time, something at an inopportune moment. That something is always the memory of something forgotten, about which we can paradoxically say "There it is again."
Follies were misunderstood, purposeless constructions. They were often only small, extravagant gestures in a garden, easily whisking off the imagination to distant lands, a sort of time capsule built to awaken the memory and induce surprise in passers-by. They marked locations, organized secondary paths in a park, or simply predicted the arrival of better times—a demarcation, a sacred spot, a mysterious trail, a hill whose tragic rocky nature begged for a tower, a party, or the arrival of summer.
“It is demonstrably true that things cannot be other than as they are. For, everything having been made for a purpose, everything is necessarily for the best purpose.” — Professor Pangloss
The details are fascinating, but the central argument — that the birth of modernity can be traced to a meta-crisis spawned by the 0.1s problem — is worth understanding and appreciating whether or not you’re a time nerd like me.
There is no convenient leitmotif, comparable to the 0.1s problem, for our contemporary version of the rhyming conditions, but something very similar to the “tenth of a second crisis” is going on today. I suspect our Great Weirding too involves some sort of limiting factor on human cognition that we haven’t yet properly wrapped our minds around. It isn’t reaction time, but something analogous.