HUGH MacDiarmid (the pseudonym of Chris Grieve) was the contentious colossus who towered over creative and cultural Scotland for much of the 20th century.

“Mac the great” was brought up in a rich Christian context, with a Presbyterian father and a very talented (and poetic) minister as key early influences, and in his teens he was an enthusiastic and formidable Sunday School teacher; but his religious zeal soon evaporated, and he became instead a determined, if erratic, foe of all organised religion in Scotland. Even so, he could never shake off the legacy of the Christianity in which he was steeped as a boy and as an adolescent. Christian references abound in his poetry.

MacDiarmid was a considerable Scottish patriot, a relentlessly cerebral, combative, heroic writer and altogether a literary titan. He certainly thought so himself; as he said, he was vain but had much to be vain about. He could sneer spitefully at other Scottish writers, past and present – yet, in just about everything he wrote, there is something that is life-enhancing and worthy of deep reflection. The word genius is much overused; but he was, without doubt, a writer of compelling, glorious genius. He was lucky in that he had a formidable disciple, the poet and journalist Alan Bold, who was 50 years younger but served, in the evening years of MacDiarmid’s long and fecund life, in the roles of minder, propagandist, apologist and indefatigable champion.

MacDiarmid was brought up in the final years of the 19th century in Langholm, near the border with England, which possibly accounts for his intense and sometimes showy awareness of his Scottishness throughout his long creative life. His father, like George Mackay Brown’s, was a postman, and was an elder in the United Free Church. The young MacDiarmid was greatly influenced by the local Free Church minister, the Reverend Thomas Cairncross, who was a distinguished poet as well as a preacher of very long and stirring sermons. Cairncross wrote many lyric poems and a book of popular Christianity called The Making of a Minister. He wrote thus of the Langholm in which he ministered: “It lies by the heather slopes/Where God spilt the wine of the moorland/Brimming the beaker of hills.”

This kind of invocation of Langholm in its own holy land probably influenced the young MacDiarmid more than he cared to admit in later life, although – never the most charitable of men – he was eventually to condemn Cairncross as a hypocrite and a careerist. Had the poet been born a little further north, perhaps in the coalfields of Ayrshire or the industrial badlands of Lanarkshire, it is quite possible that he might not have experienced Christianity at all in his youth. In that case, he could of course not have rejected it as a young man; he might even have embraced it, with that persistent ardent contrariness that was his defining characteristic.

As it was, from his late teens, MacDiarmid was a consistent (and consistency was not usually one of his virtues) atheist: His son Michael Grieve assured me of this more than once in conversations I had with him much later.

But that does not mean that MacDiarmid should not have a place in this esoteric survey. He never wholly shook off the shadow of the Reverend Thomas Cairncross, despite appearing to resent it bitterly. In his maturity, he could praise what he called the “tremendous” message of the Sermon on the Mount, and at the time of his nervous and physical crisis in the mid-1930s he referred to the “certainty” of the Resurrection.

I think his avowed atheism should be seen as of a piece with his intermittent communism and consistent socialism; he saw it as an organised and effective way of dealing with the “interdependencies of life”. Although a lot of his writing was self-consciously cerebral and political, much of it was also infused with mystical and spiritual depth.

Despite this, he was an engaged, practical citizen, rooted in everyday matters; he did not eschew civic life. For a time, he was an industrious if somewhat wayward newspaper reporter, he served as a town councillor in Montrose, and he was also a Justice of the Peace. He was a committed, if again somewhat erratic, Scottish nationalist. (He managed to get expelled from both the Communist Party of Great Britain and the Scottish National Party, though not at the same time.) He had periods of retreat, especially in Shetland, but for most of his life he was committed to intensive public activity. He was on an eccentric and often vituperative mission to revitalise, and even to reinvent, not just Scots literature and the Scots language, but the nation itself.

IN THE First World War, he served as a sergeant in the RAMC in Salonika and France; in the Second World War, he contributed resolutely to the national effort by working – hard, for a man who was almost 50 – daily ten-hour shifts as a fitter at Mechan’s Engineering Yard at Scotstoun on Clydeside. The work was physically exhausting, and he was transferred to the copper shell shop. Here he suffered a serious industrial accident when a heavy pile of copper plate collapsed on him, injuring both his legs and one of his arms, and almost killing him. (This is not the kind of thing that happens to many middle-aged poets in the workplace.)

At this time, he was staying with his brother, Andrew. Their relations were hardly fraternal; indeed, they loathed each other. MacDiarmid was very good at making, and keeping, enemies, and he treated his long-suffering brother as an enemy rather than a host. As soon as he recovered from the accident in the copper shop he worked briefly as a postal worker further down the Clyde at Greenock, which, at this time of war, was the busiest naval port in Britain.

Through contacts he made there he became a deckhand on a Norwegian vessel that was supporting larger vessels of the US and British navies in the Clyde estuary. (Significantly, these wartime roles he had in the 1940s lacked rank, and were humbler than his service as a senior non-commissioned officer in the First World War.)

A small and not particularly strong man, he drove himself on with an almost crazy zeal for life, for controversy and disputation, for literature and for hard work. And, above all, for Scotland. He packed an enormous amount of varied experiences into his long life which even, for a short time, encompassed being the headmaster of a tiny school in Easter Ross. Those who criticise or debunk him should always remember how hard he worked and how engaged he was.

Unremittingly combative and ferociously intelligent, he was a much more intellectual poet than Burns, though he does not seem to touch human beings in their millions as Burns does. But he was constantly reaching for his own soul, and for the soul of Scotland at the same time; many of his poems are charged with an undoubted, and moving, spiritual questing. His rejection of Christianity does not mean that he was without spiritual ardour; far from it.

To paraphrase from his best, longest and most difficult poem, A Drunk Man Looks at the Thistle, he could hear eternity dripping drop by drop; and he heard God passing with a policeman’s feet, in the long coffin of the street. His drunk man refused to be crushed by “the echoes of that thundering boot” as he saw a monstrous thistle (an awkward and prickly symbol of Scotland’s soul).

So, the thistle in this extraordinary, long and ambitious poem – quite possibly the most ambitious poem of the 20th century – is an ambivalent (and, of course, Scottish) sign pointing, in a rather confused but powerful way, to what Scotland is searching for. The eponymous drunk man is a splendid creation. He comes to realise that he can’t see Scotland if he can’t see what is infinite. His boozed-up contemplation of the complexities of Scotland reaches unlikely if ironic heights as he gradually becomes “a greater Christ, a greater Burns”. (In today’s Scotland, the latter is probably regarded by many as more provocative than the former.)

The poem, which is cerebral and satirical rather than emotive, is at first a paean to inebriation, then a gloriously idiosyncratic celebration of Scotland, and ultimately a complex statement, replete with many literary references, of ethereal and spiritual – if only obscurely Christian – inquiry.

The drunk man starts off as a typically tiresome inebriated Scotsman but slowly progresses beyond mere drunkenness into a profoundly spiritual state where he not only identifies with the destiny of Scotland – whatever that might be – but also achieves an unlikely oneness with the entire created universe.

From the petty and pathetic worry of having to crawl home to face the wrath of his girning wife (a Burnsian concern), he soars away from this dreary reality and finds a transforming resurrection. The thistle, which had been “grisly” and “Presbyterian”, has become, as if by magic, the key to the entire universe – and beyond. The drunk man does not so much look at the thistle, and all that it represents, as grapple with it.

MacDiarmid was determined to write in Scots for literary and political purposes; A Drunk Man is in Scots, sometimes difficult and recondite Scots. He tried, and failed, to reinvent Scots as a living language, used routinely in everyday life. But he succeeded in reinventing it as a literary language. He also, later in his career, wrote sublimely in English. Some of his early Scots lyrics are particularly beautiful. They were published in the Glasgow Herald, which supported him when he was making his way in the literary world. To the paper’s great credit, it also published extracts from A Drunk Man, a difficult and very controversial poem; this showed real editorial confidence and vision.

MacDiarmid was an enormously complicated man; he often contradicted himself. Well aware of this, he suggested that his “job” was to erupt like a volcano, emitting not only flame but also a lot of rubbish. Even at the various times when his body was weak and ill, he remained truculent and fierce.

With considerable self-knowledge, he once said that he would fight hard for a communist state, and, once that was achieved, fight hard to get rid of it. He strove relentlessly, without any concern for his mental or physical condition. His literary output was huge, especially if his prolific journalism is also taken into account.

It’s not surprising that he suffered a serious mental and physical crisis in 1935. But he recovered fully, and continued on his contrary and disputatious way until he died in 1978, aged 86, a brave and feisty battler for so many causes, lost and won. For me, he was by far the greatest Scot of the 20th century. A case could be made for him being the greatest Scottish writer of all, bar none. If his political diversions and polemical ramblings could sometimes be tedious, there is no denying his literary integrity.

Few, if any, other Scottish writers have been so devoted to their art.