IT may be the silliest, most chauvinistic question ever. But the temptation to ask it cannot be resisted. Was the most important book ever born in Scotland?

The inquiry may be crass, the answer cannot be definitive, but the influence of The Varieties of Religious Experience cannot be questioned. Simply, but unequivocally, it can be said to have saved lives. Thousands? Hundreds of thousands? Who knows?

Yet it remains relatively unknown and largely unread. It may even demand an introduction. Here it is.

The author of The Varieties was William James, born of Scottish/Irish family in New York in 1842. His brother Henry scribbled a bit, too. The Varieties consists of the Gifford Lectures William James gave at the University of Edinburgh in 1901/1902. A philosopher, psychologist, writer and spiritual seeker, the work of James might, after more than a century, be expected to have been rendered outdated or even irrelevant.

Yet it lives on daily in church halls, community centres and rehab centres all over the world, with many who are influenced by his ideas, perhaps even transformed by them, having no idea of his name or reputation.

The explanation for this phenomenon is simple. William James has been described as a co-founder of Alcoholics Anonymous (AA) by Bill Wilson, a fellow co-founder, who never met his fellow countryman. The Varieties of Religious Experience is the only book cited in Alcoholics Anonymous, the textbook on how to recover from addiction.

More than a century on from James delivering those lectures in Edinburgh, his work and belief have gained greater authority through the decades. So what did James say in those 20 lectures and why have they been so influential and enduring?

To be almost crudely brief, James argued that reality should be confined to what we experience and that a spiritual experience could be either dramatic or educational. Thus human beings could be transformed by sudden religious experiences such as that which subsequently befell Wilson, recovering from an alcoholic binge in hospital, or, for example Eckhart Tolle, the spiritual teacher and writer of The Power of Now. They were both changed by extraordinary events. Wilson wrote of being “caught up in an ecstasy which there are no words to describe”. Tolle, decades later, endured a heavily anxious night, then had a moment of revelation followed by a feeling that “everything was miraculous, deeply peaceful’’.

These type of experiences, of course, have been recounted by religious figures down the ages from the Buddha to St Theresa, but how do they impact on the mass of humanity, particularly those who were anxious, addicted or depressed? Or all three.

James argued that change could be brought about by personal actions. He found solace from his depression in his philosophical writings. Wilson grabbed the theory that spiritual experience could be of the “educational variety”. He, and the other writers of the book Alcoholics Anonymous, distilled this approach to the mechanism of the 12 Steps. They are not far removed from the Six Steps of the Oxford Group, a Christian organisation most influential in the 1930. They hold, too, to the tenet of the Spiritual Exercises of Ignatius of Loyola that transformation is not restricted to a sudden, inexplicable gift from the divine but is also something that can be sought and achieved. Seek and ye shall find, as it were.

The crucial importance of the Wilson approach, though, was he not only directed it at alcoholics but firmly believed, with support from Carl Jung, that the suffering alcoholic could only recover through a spiritual experience. The AA model has been adopted by those suffering from other addictions, such as narcotics, gambling, sex and eating. The very term addiction has been questioned, the methods of AA and fellow groups criticised, but many – who knows how many – have recovered.

Yet as the world heads towards the third decade of the 21 century, the experiences of James and Wilson have become even more intriguing. James investigated mystical experience by experimenting at times with drugs such as chloral hydrate, amyl nitrate and peyote.

In 1956, Wilson followed James down the path of taking a drug to see if it could induce a spiritual transformation. He took first “acid trip” using LSD, then a legal drug, at the Veterans Administration Hospital in Los Angeles. Wilson felt LSD “helped him eliminate many barriers erected by the self, or ego, that stand in the way of one’s direct experiences of the cosmos and of god”. His official biography also reported that he “thought he might have found something that could make a big difference to the lives of many who still suffered”.

This personal belief never found favour among the mass of AA members and the book of Alcoholics Anonymous remains largely unchanged, with only minor edits and added footnotes, since its publication in 1939.

However, a new book adds substance to the belief that psychedelics can have transformative, beneficial effects. Michael Pollan’s How to Change Your Mind offers evidence of the extraordinary ability of psychedelic drugs to treat depression, addiction and existential anxiety, the latter most particularly in patients with terminal diseases. The figures can be mind-numbing: 80% of cancer patients reported reduction in anxiety and depression for at least six months following a session with psilocybin (magic mushrooms, crudely).

There is, of course, the health warning from Pollan that “no-one with a family history or predisposition towards mental illness” should take psychedelics, but the medical world is waking to the potential uses of such drugs.

It illustrates that there may be many ways to cosmic consciousness, a glimpse of the divine or the transformative effect of the diminution of the ego.

James, of course, investigated many, both through personal experience and by professional observation. In a world that rapidly moves on, quickly dismisses or disproves the past, he remains valid and wise. It is why he and The Varieties of Religious Experience remain important, perhaps so long as mankind both suffers and searches.