“Nothing about the opening this month of the (Philadelphia Museum of Art’s) Ruth and Raymond G. Perelman Building – the first public addition since the opening of the neoclassical temple in the 1920s – makes the (institution’s) mission less serious. But the 173,000-square-foot expansion represents the museum’s only suggestion in decades that its art is not necessarily tied to a building, and that it is ready to come down off its pedestal, literally and figuratively, to become part of a city neighborhood.”