THE "spiritual but not religious" are the largest group of individuals in the UK, the think tank Theos says in a recent report on "belief in post-religious Britain". Its recent poll, which shaped the inaugural discussion on the new Things Unseen podcast (www.thingsunseen.co.uk), found that only 13 per cent of those questioned agreed that human beings are purely material, with no spiritual element ( News, 25 October). That much may be unsurprising to members of the Church of England who routinely work at the interface of regular and irregular churchgoers.

What does seem to be a new phenomenon, however, is that avowedly secular groups are seeking to explore a spiritual dimension - and not just privately, but through meetings and action. One example of this is the Sunday Assembly, also called the "atheist church", although its founders are keen to emphasise that Dawkins-like rallies are not its raison d'être. In only a few months, it has drawn hundreds of people and led to several "church plants" (News, 25 January).

Some people will be sceptical about this new spiritual questing, much of their unease focusing on the word "spiritual". In much the same way as "sin" now spontaneously throws up associations of chocolate and lingerie, so "spirituality" can mean little more than warm feelings and a fondness for scented candles. They might ask where the ethical engagement is in this touchy-feely piety; where is the embrace of suffering, or the intellectual weight?

THE whole question is being tackled head-on by another self-consciously secular organisation, the Royal Society of Arts (RSA) in London. Founded in 1754 at the height of the English Enlightenment, and usually associated with practical policy development, the society became interested in recent studies on human well-being.

The "S"-word kept coming up, particularly in the domain of positive psychology, the academic movement that lies behind many of the current political attempts to think about mental health as well as economic wealth. It identifies spirituality as a "signature strength".

Now, one of the directors at the RSA, Jonathan Rowson, is leading a year-long project, which will include workshops and public events, to help make spirituality "more tangible and tractable".

He believes that the evidence shows that personal growth and social engagement are nurtured when people have a spiritual perspective, are informed by spiritual experience, and shape their lives by spiritual practices. He argues that the world's main policy challenges, from climate change to rising levels of obesity, may ultimately be spiritual in nature, because they are about our struggle to align our behaviour with our values.

Spirituality addresses such inner conflicts. That so many people seem unable to resolve them may be, in part, a product of a culture that is starved of that which can motivate us at the deepest levels.

The first of the public events was held in October (the discussion can be found as a podcast on the RSA's website), and it was striking how apologetic the contributors were for even talking about the subject. Mr Rowson thanked the head of the RSA, Matthew Taylor, for the "reputational risk" involved in sponsoring the project.

Other participants talked of feeling nervous and unsure, even while confessing that religion was central to their lives. Spirituality has become a kind of taboo. Intellectuals, politicians, the media, and even members of the clergy can be as embarrassed by it, as Victorians supposedly were by exposed piano legs. 

THIS must be because we live in a world that has been profoundly shaped by a rejection of the spiritual dimension. The theologian David Bentley Hart makes this case in The Experience of God (Yale University Press, 2013), arguing that the philosophical and scientific paradigms that shape the contemporary imagination have put off-limits subjects such as faith, the soul, and the implicit.

"The philosophical tendencies and presuppositions of any age are, to a very great degree, determined by the prevailing cultural mood or by the ideological premises generally approved of by the educated classes," he writes.

I think that this is true. Listen to BBC Radio 2 or 4 any day of the week, and you will be drawn into a world-view that finds evolutionary speculations about the origins of love or of music, for example, engaging and acceptable, whereas wondering about truth or transcendence gets kid-glove treat- ment.

That spiritual sensibilities, the sources of human purpose and meaning, are ring-fenced is surely part of the reason why we find ourselves so frequently to be ethically and personally at sea. 

PERHAPS the nascent secular interest in spirituality marks a change. The task of redressing the imbalance is about nothing less than shifting mindsets, but when unexpected parties - such as the RSA or self-conscious atheists - come out about spirituality, new connections become possible.

Conversely, those who needed no persuading, but find the "S"-word difficult, must swallow their disdain, and be prepared to treat the word as a placeholder for a society striving to revive these half-forgotten insights about what it is to be human.

I suspect that some steps will be easy to make. As the philosopher Robert Rowland Smith put it during the RSA discussion, many well-meaning people can agree on a notion of spirituality that is essentially a form of ethical humanism: the intuition that community, wonder, and helping others adds value to life.

But this does not get to the heart of what is meant by spirituality. It is, rather, engaging with the possibility that the source of human vitality and purpose ultimately lies beyond human capacities and understanding; that life is sustained by what theists call God.

The difficult moment for the new spirituality will arrive when those who have put their faith in secular enlightenment are confronted with the possibility that it is not enough.

Mark Vernon's latest books are Love: All That Matters (Hodder) and Carl Jung (Guardian Shorts).