YOGA has been in the news a lot recently. As colleagues have written, the establishment of International Yoga Day, celebrated for the first time last Sunday was a significant milestone for India's "soft power" and on balance, a personal success for Narendra Modi, the prime minister who led 37,000 people in a display of the spiritual exercise. Yoga also generates headlines in countries far from India, both because of its widespread appeal and the mixed feelings (to put it mildly) that it engenders among followers of the world's monotheistic faiths.

Malaysia and Iran stand out as Muslim countries where yoga is both quite popular and controversial. In 2008, when Malaysia's supreme Islamic authority told Muslims to eschew the practice, this was widely greeted with dismay as a symptom of a hardening theological line in a country where many faiths have to rub along. Abdullah Ahmad Badawi, the (devoutly Muslim) prime minister at the time, later specified that it was permissible to do the exercises as long as people held off from Hindu chanting.

In Western nations which are historically Christian but increasingly diverse in their approach to things spiritual, the very ambivalence of yoga (call it flexibility if you like) is one of its selling points. Depending on which school of yoga you follow and how far you go, it can be a way of limbering up the body and easing tensions, or it can involve the pursuit of extra-ordinary spiritual experiences, culminating in samadhi, variously described as union with, or absorption into, ultimate reality. It is agreed that yoga has its roots in the Hindu tradition, and that it constitutes one of the main schools of Hinduism; but it can of course be practised as a physical and even mental discipline by people who are ignorant of, or even mildly resistant to the teachings of Hinduism. That point is made defensively by many Western yoga teachers, and with dismay by purist advocates of the Hindu path.

Traditional Christian clerics still see dangers in the practice. In the Northern Irish city of Derry-Londonderry, a Catholic priest caused a local furore in February by telling his parishioners that yoga, and even Indian head massage, could open people to demonic influences. Around the same time, a Church of England priest in Bristol told a yoga teacher who had been instructing hundreds of people on church premises to find other quarters. The teacher, Naomi Hayama, complained bitterly, on grounds that her kind of yoga, at least, was certainly not an alternative faith. "They are trying to say that is a spiritual practice but my classes are not. I respect people who are religious but I am not," she said.

Even in North America's culturally liberal West, yoga attracts controversy. albeit for different reasons. In Vancouver last weekend a plan by the provincial government to have a yoga event on a central city thoroughfare was cancelled at the last moment: some people thought it would distract attention from National Aboriginal Day, and others resented the fact that two of the event's corporate sponsors were also big donors to the Liberal party which runs British Columbia.

Across the United States, there are plenty of advocates of "Christian yoga"; but an evangelist and physical education instructor, Laurette Willis, has also had some success with a a system of body postures called PraiseMoves which is explicitly linked to Christianity; she says she dabbled in Eastern religions for a long time before coming to the conclusion that yoga postures were prostrations before Hinduism's multiple deities and therefore incompatible with belief in Jesus of Nazareth.

At a more senior level, some Christian leaders have held back from attacking yoga as such but urged followers not to treat it as an easy alternative to their own spiritual calling. The former Pope Benedict, in his earlier days as Cardinal Joseph Ratzinger, observed that "some physical exercises automatically produce a feeling of quiet and relaxation" and warned people not to "take such feelings for the authentic consolations of the Holy Spirit." Pope Francis, in a homily earlier this year, was more tactful, but still edgy: he included formal Catholic instruction or catechism, along with yoga, on his list of things which should not be seen as a proxy for the mysterious power of the Holy Spirit to stir human hearts.

You can take a million catechetical courses, a million courses in spirituality, a million courses in yoga, Zen and all these things. But all this power will never be able to give you the freedom of being children of God.

And if you are looking for more categorical denunciations of yoga from top Christians, you can certainly find them. Albert Mohler, an influential leader of America's evangelical camp, has told Christians to stay away from stretches, and the Orthodox church of Greece issued a similarly clear-cut prohibition last week. On the other hand if you are a Christian or Muslim who loves the lotus, you can find plenty of well-rehearsed arguments for the compatibility of the Indian practice with Abrahamic monotheism. A Christian web-site, for example, argued that evicting yoga-lovers from the premises in Bristol would do more harm than good. "Doing yoga doesn't make you a Hindu or a Buddhist any more than singing along to George Harrison does."

In his attack on yoga, Mr Mohler described India as "almost manically syncretistic" in other words, prone to the mixing of religious ideas. But the fact is that most Western societies, insofar as they think about religion at all, are pretty syncretistic too. That puts traditional Christian or Muslim leaders on the back foot when they try to argue against the asanas.