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
In our use of digital and analogue filing tools, we classify information through folders. An article about railway construction gets filed under ‘infrastructure’ or ‘transport’. In Evernote we tag it with ‘rail’ or ‘construction’. This is thinking like a librarian and not like a writer. We are classifying the information as an input. The reason you take notes as a writer is to produce content. It makes sense, then, to take notes in line with this goal.
Traditional filing like this tends to fail when you attempt to write your content. You are stuck trying to figure out which categories will be relevant for your proposal, paper or blog post. Interesting writing often comes from connecting separate fields through a common idea. By revealing the common denominator. By unifying two seemingly-contradictory ideas. How can you possibly achieve this if you’re looking in the same category for your information? The categories simply do not fulfil the function required by the writer.
The notes you take and indeed, the way you process information, should be with a specific project or idea in mind. You must classify information in terms of its outputs. When you take notes on a book, think about how this could apply to a specific idea you had or how it argues against a paper you read last week. The premise is that you should be organising by context and always trying to connect the dots between the content you're consuming.