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
It is a concept based not on the classification of various physical features of architecture and urban design but on the problem-solving process itself. We have seen that the final outcome of a design process is strongly determined by at least three aspects of that process:
the subject matter of the organizing principles which are adopted,
the manner in which these principles are interpreted and reinterpreted in the context of the problem at hand, and
the sequent of applying such organizing principles.
Consistency in style among the output of designers can thus be understood as a habitual way of doing things, of solving problems.