London

'Multiculturalism has failed," said British Prime Minister David Cameron last weekend in Munich. If anybody thought they had read those words before, it is because they have. Many times. Last October German Chancellor Angela Merkel (sitting onstage with Mr. Cameron when he gave his speech on Saturday) said the same. Finally, Europe's mainstream party leaders seem to be realizing what others have long noticed: Multiculturalism has been the most pernicious and divisive policy pursued by Western...