A FRIEND told me a story about a woman he knew who moved to the Isle of Lewis. On her first Sunday she hung her washing on the line and went for a stroll. When she returned home her clothes had been taken down, neatly folded and placed on her front door step with a note: “We do not do washing on Sundays”.

These seven words are testament to the unique culture of Lewis and Harris, the determined nature of the inhabitants, their Presbyterian strictures, and their forthright notion of community. The author, activist, and scholar Alastair McIntosh knows all about this island life. He grew up in Leurbost, on the east coast of Lewis. His most famous book, Soil and Soul: People Versus Corporate Power, gives an account of his childhood and outlines his philosophy of human ecology and liberation theology. It also documents his involvement in the struggle for land reform on the Isle of Eigg and the campaign against a proposed super quarry on Harris.

In 2009 McIntosh felt the “winnowing call” of the island of his youth. He returned for a south-north walking tour to explore the spirituality of the place, from its relatively modern Calvinist tradition back to its Celtic roots and faerie culture. Lewis and Harris are chock-full of spiritual landmarks, from the many bothans, or “‘beehive’ dwellings of corbelled stone”, to the Neolithic standing stones at Callanish. McIntosh starts his trek at the southern tip of Harris, at Saint Clement’s Church of Rodel, one of two restored pre-Reformation chapels on the island. He then winds through the mountains of Harris. After crossing the Grimersta, a river that “bellows from the island’s heaving heart and surges to the sea”, he moves through flat moorlands to the island’s northernmost point, the Butt of Lewis.

This spiritual and physical homecoming is a way for McIntosh to reflect on his work on war and peace. As he points out, you will not find many people who have been “put on trial for protesting against Trident nuclear submarines” and been a lecturer for the UK Defence Academy, the educational college for the British armed forces. McIntosh has had this latter role since the late 1990s. Unlike juniors, senior army personnel are encouraged to “think independently”. McIntosh, a lifelong peace activist, provides them with the “alternative point of view”. In 2009, while Iraq and Afghanistan were “smouldering”, he attended a Nato peace conference on God, War and the State. He watched a rich Arabic man strike match after match and let them burn down. “It felt like witnessing a countdown … the final stage, before ignition, of my pilgrim journey’s launch.”

McIntosh’s own religion is idiosyncratic. He believes a deep spirituality binds life together, but he is not in thrall to any one God or religion. He describes his own writing as “too Christian for the Pagans and too Pagan for the Christians”. A free spirit, he has no problem showing the damage religion has inflicted on the world.

It is telling that Trijicon, an American arms manufacturer owned by a devout Christian from South Africa, supplies sights for British infantry firearms. The sights currently on issue to the British infantry have Psalm 27:1 coded into each model number: “The Lord is my light and my salvation. Whom shall I fear?”

IF this sounds more serious than a Presbyterian church service, there is great fun to be found in A Poacher’s Pilgrimage. McIntosh is an entertaining subversive. For many islanders, pilgrimage is a form of papist superstition. So, whilst keeping that side of his journey quiet, he tells suspicious locals he is there to undermine the game protection laws the landed classes created to give themselves exclusive access to the lochs and rivers bursting with fish. Suffice to say, McIntosh takes his rod. This playfulness matches his writing style, which is jovial and extravagant. He is prone to hyperbole, which can be satisfyingly odd – “God is the primal atom of delight” – but, at times, queasily emotional.

What makes A Poacher’s Pilgrimage enjoyable is not so much the outward journey, moving as it does from bog to chapel to bothan to holy well and back to bog again, but McIntosh himself. If he were not real, he would have to be a character straight out of Dickens. He can become fascinated over an empty jam pot or his walking boots, then embark on a serious theological examination of the links between Calvinist theology and American exceptionalism. His knowledge is astonishingly varied and far-reaching. He can talk theology, science and myth with scholarly aplomb.

One of the most memorable aspects of the book is the diverse cast of characters. McIntosh is a consummate conversationalist, at home with British soldiers, church elders and atheists alike. He does not shy away from difficult questions. In his search to understand how violence affects the mind, McIntosh asks a British soldier how killing someone has changed him. “I feel the cold more easily than I used to,” comes the reply.

Near his journey’s end, McIntosh visits the notorious atheist Doctor Finlay McLeod, who, according to one islander, is “less of an atheist than he’s pretending not to be”. Upon meeting, the pair do a pagan jig on the front lawn, just to impress the villagers. They might well scowl, but one thing is for certain, none of them will be going near Doctor Finlay’s washing line anytime soon.

Poacher’s Pilgrimage: An Island Journey by Alastair McIntosh is published by Birlinn, priced £20