Gerhard Richter (b. 1932) is one of the most influential artists at work today. His painting September, a response to the attacks on the World Trade Center on September 11, 2001, was made some four years after the event. The eminent American critic and curator Robert Storr, who has had a long working relationship with Richter, explores both the painting and the event itself, through a very personal account of his experience in New York on...