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
Thus the first and most important stratagem adopted to cheapen construction was the squaring and turning of components in order to eliminate offering up and individual fitting. The flatness, straightness, and squareness which more than any other characteristic distinguish man's construction from the works of God, derive from economy. We see the mark of economy in every building of squared masonry however magnificent it may be. Only the few remnants of ancient polygonal masonry remind us that the pattern of stone work where each stone is individually fitted can be very different from the cheap squared pattern to which we are accustomed."