It was around 1935 or 1936 that I first had the idea of compiling a history of art – not in the usual way, but considering only the fads that have succeeded one another down through the ages. For example, the infatuation in Roman times with broken pleats and heads turned in profile.... or during the epoch of Pérugin and Raphael, a certain blue that appears everywhere. I wanted to draw up an inventory of these vogues. To this end I visited museums, took notes in little notebooks, and made demonstrative sketches of paintings. For this purpose I preferred bad paintings, by which I mean those held to be mediocre by aesthetes, but in which these fads that interested me were clearly in evidence.