In 1939, and in response to the massive Mostra Giottesca of 1938, Roberto Longhi wrote a sour, intentionally provocative piece that he curtly called his Guidizio sul Duecento, or judgment regarding the thirteenth century. In the essay, Longhi fretted that writers on medieval art had become so absorbed in establishing the authorship and origins of images that they had largely forgotten to act as responsible critics. They had thus also begun to forget that the...