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
I worked for several years as a leader of birding tours, and I have met a few sad individuals who were so focused on adding to their life lists that they would refuse to look at a bird species that they had seen before, no matter how spectacular the view or how fascinating its behavior of the moment might be. “I don’t need that bird” was their standard reply.
For a person just getting started in some area of natural history, and unabashed focus on list-chasing is a good thing, at least for a while. The trick is knowing when to stop.
Keith Brown described how he got the idea “that the maximization of daily species lists of butterflies, a seemingly unscientific goal (though much employed in a sister area, ornithology), could give a large scientific fallout."
For example, he described how six weeks’ effort in the Brazilian central plateau had turned up twenty-five species previously unknown for the area—but then he had adopted the “maximization” method, and in another six weeks, he had found nearly three hundred more species.