“I am very much afraid of definitions, and yet one is almostforced to make them. One must take care, too, not to be inhibited by them.” Sowrote painter Robert Delaunay to his fellow artist August Macke in 1912, a timewhen the art world was having something of an identity crisis, hovering betweencolorful, cubist figuration and the pure abstraction of later painters such as PietMondrian and his De Stijl cohorts. The period—as most of the 20^thcentury’s important art movements—is amply represented in the collection ofPeggy and Solomon Guggenheim, which will be plain to see at a new exhibition ofearly abstract works from the collection, opening February 20 at the imposingByzantine church of San Marco, Vincelli, Italy.