Such ideas have become powerful in the West, partly because of arithmetic: we now have a great many Muslims in our midst – far more here, proportionately, than in Mr Trump’s country, and more in France than here. The risk of violence rises with the total. Even if it is true that 99 per cent of Muslims would not hurt a fly, when you increase the numbers you inevitably get more of those who would. People are, therefore, right to worry more about mass immigration from, say, Syria, than from, say, Poland.