I. THEY ARE, in their very different ways, monuments of American civilization. The first is a building: a grand, beautiful Beaux-Arts structure of marble and stone occupying two blocks’ worth of Fifth Avenue in midtown Manhattan. The second is a delicate concoction of metal, plastic, and glass, just four and a half inches long, barely a third of an inch thick, and weighing five ounces. The first is the Stephen A. Schwarzman Building, the main branch of the New York Public Library (NYPL). The second is an iPhone.