Christianity is growing faster in the Islamic Republic of Iran than in any other country in the world. That is the extraordinary claim recently made by the Christian Broadcasting Network (CBN), founded by televangelist Pat Robertson. An accompanying report suggested that roughly 20 per cent of the country’s 80 million population have viewed Christian programmes via satellite or mobile phones.

The CBN does, of course, have an incentive to exaggerate evidence of a shift towards Christianity in Iran. Yet there is no doubt that the faith is winning converts in a country where belief in Jesus can result in imprisonment. A 2015 study by Duane Alexander Miller of St Mary’s University in San Antonio and Patrick Johnstone of WEC International, an Evangelical organisation in Singapore, suggested there were 100,000 Iranian converts to Christianity between 1960 and 2010. But given the regime’s strong disapproval of conversions, it is impossible to know if this figure is accurate.

Miller and Johnstone calculated that, in 2010, there were between five million and 16 million Islamic converts to Christianity worldwide. The United States is a particular hotspot. Dudley Woodbury, a Fulbright scholar of Islam, estimates that some 20,000 Muslims in the US become Christians every year.

There are reports of mass conversions in Europe, too. In 2016 more than 80 Muslim refugees from Iran and Afghanistan were baptised at a single ceremony in Hamburg. That same year, Cardinal Christoph Schönborn reported that the number of converts from Islam in his Archdiocese of Vienna had “increased considerably”. More than half of recent adult converts, he said, came from Islamic background and “I myself have baptised many Muslims”. This was striking given the Church’s reticence about pursuing conversions in the Islamic world after Vatican II insisted on dialogue rather than proselytism.

Lest we get carried away, we must set this phenomenon within its wider context. According a Pew Research Center study last year, Islam is projected to be the world’s fastest-growing major religious group in the coming decades. Babies born to Muslims will begin to outnumber Christian births by 2035. Although there are no reliable statistics, we also know that, anecdotally, there are a significant number of Christian converts to Islam.

But some Muslim intellectuals worry that this demographic strength masks the fragility of Islamic culture. In a recent New York Times article, the Turkish writer Mustafa Akyol argued that “if Islamic authoritarianism persists, it is likely to produce mass secularisation in Muslim societies. Islam may still count as the fastest-growing religion in the world, thanks to high birthrates, but it will lose some of its best and brightest.” According to Akyol, a minority of these ex-Muslims will become Christians. Most will be classified as religious “nones”, who, according to Pew, are the third-largest group in the world after Christians and Muslims. Both Christianity and Islam are contributing generously to the proportion of “nones”, which is 16 per cent of the world’s population and rising.

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