The Chinese have a pious habit of copying their old masters' paintings and signing the masters' names to their copies out of respect. That practice makes a muddle of most Chinese art collections.
Last week, for perhaps the first time in history, Manhattan gallerygoers saw a private collection of Chinese masters they could be sure of. The paintings dated from the 8th to the 18th Centuries; each of them had been traced all the way back and authenticated by one of the few living connoisseurs who really can: a Shanghai collector named Chang Ts'ung-yu.
Among the best pictures in the show was a...