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 true that [the artist], like everybody else, derives remuneration from his work (though not, strictly speaking, profit in the financial sense, of the word, since what he invests in his work is not money but time and skill, whose returns cannot be calculated in percentages). The remuneration is frequently beyond the amount necessary to enable him to go on working. What is remarkable about him is the way in which he commonly employs the escape-from-work which the extra remuneration allows him. If he is genuinely an artist, you will find him using his escape-from-work in order to do what he calls “my own work”, and nine times out of ten, this means the same work (i.e. the exercise of his art) that he does for money. The peculiar charm of his escape is that he is relieved, not from the work but from the money.
What distinguishes him here from the man who works to live is, I think, his desire to see the fulfilment of the work.