“You obviously want the viewer to participate in the act of seeing, and they can do this by trying to understand how the work is made,” Ai Weiwei tells me as we examine his colorful and colossal LEGO brick works on view in “Child’s Play,” an exhibition spanning two Vito Schnabel Gallery locations in Manhattan. “Everybody has some toy-building and digital gaming experience, so that attempt to understand becomes interesting when looking at the work. But it’s not just about construction, it’s about...