LONDON — The number of people proclaiming their faith worldwide is growing. This is clearly so in the Islamic world. Whereas Europe's birthrate is stagnant, the Arab population is set to double in the coming decades, and the population will rise in many Asian Muslim-majority countries.

Christianity is also growing — in odd ways and in surprising places.

Religion's largest growth is in China. Indeed, the religiosity of China is worth reflecting on. There are more Muslims in China than in Europe, more practicing Protestants than in England, and more practicing Catholics than in Italy. In addition, according to the latest surveys, around 100 million Chinese identify themselves as Buddhist. And, of course, Confucianism — a philosophy rather than a religion — is deeply revered.