THE Dream of the Rood is an old poem that represents Christ’s human sacrifice through words delivered as if spoken by the cross itself. It’s an extraordinary act of sympathetic imagination, telling us what it was like to bear the weight of the body of the man who died to save humankind, the pain and shame as the nails tear through his body and into its own. Whatever religion you espouse or refuse, whatever humanism you prioritise, should never cut you off from such a work of insight, imagination and sympathy.

Around the year 700, someone who had a particular love for this old poem had words and phrases from it etched into a tall stone sculptured cross, and if you travel to Ruthwell, near Dumfries in the south of Scotland, you can still see the Ruthwell Cross. The fragments of the poem are in Anglian, which has been confusingly described as “North-West Northumbrian Old English” or “South-Eastern Dumfriesshire Old English”. The language relates to modern Scots as Saxon does to modern English. Edwin Morgan described the Ruthwell Cross as solid Dumfriesshire red sandstone, weathered but preserved, and the crucifix it is modelled on is a tree of victory: “Christ conquers death, but poetry conquers silence and gives a voice to dead wood [or in this case, to stone], and the book (made from wood) gives a voice to forgotten traditions.” The poem is a memorable evocation of the human sacrifice crystallised in the image of Christ’s crucifixion. And understanding the meaning of that doesn’t require your commitment to Christianity.

A century on, a major figure in the tradition of Christian philosophy is Johannes Scotus Eriugena (c815-77), whose great work, De Divisione Naturae, appeared c867 AD. Eriugena worked out his own understanding of the divisions of nature and attempted to define the constitution of the universe in four categories, beginning with God as origin and concluding with God as the end to which all things return. The orthodox considered this pantheistic. At the heart of the whole thing is a problem later millennia returned to in the question of predestination and free will. God is perfect, by definition, but to create the universe and everything in it, including people, He must have moved, because you can’t create without moving. This is admitted. But God, being perfect, can’t move because perfection can’t change. This is also admitted. So there’s a problem.

The answer, maybe, is that perfection can change, be different in different parts of the world, for different peoples, and at different times – but that would allow a human dimension to the word. But this is not allowed. Then there really is a problem.

The problem had been considered in multiple permutations by the early 6th-century Roman philosopher Boethius, in The Consolation of Philosophy (523-34 AD), which asks hard questions about free will and predestination: How can people be happy in an unreliable world? What is the value of the work of the mind? In 2015, a manuscript copy of the book dating from 1130-50 AD in Glasgow University Library was identified by researcher Kylie Murray, not as English, as had been believed, but rather closely resembling work from Kelso Abbey in the Scottish Borders, from the era of the Scots Kings David I (1124-53) and Malcolm IV (1153-65). This manuscript was a product of the Scottish kingdom. Boethius was being read in Scotland 300 years earlier than previously thought, proof of a flourishing intellectual and literary culture in a Scotland many would like to caricature as backward and impoverished. Boethius wrote the original in prison, awaiting execution (in Pavia, in what would become northern Italy): the problems he addressed were close, pressing and real. They are political and human as much as theological, and are always with us.

Another major figure in the philosophical-religious tradition is Duns Scotus (c1266-1308), born as his name indicates in Duns, Berwickshire, in the Borders (there’s a statue of him in the public park there, dating from 1966). Contemporaries knew him as Johannes Duns. Educated at Oxford and possibly at Cambridge too, he lectured at the University of Paris then went to Cologne around 1307, where he died quite suddenly the following year. The central tenet of his philosophy has exerted enormous influence in the 20th century: “haecceity” or the “thinginess” of things, otherwise called “thisness”. This underlies the dictum of the American poet William Carlos Williams (1883-1963), “No ideas but in things” – in other words, abstractions are useless unless they’re earthed in reality, arise from or come out of material objects, facts, things. Scotus’s theological argument about “univocity of being” connects with this in that it endorsed the idea that words used with reference to God must have meaning with reference to human understanding, so that when you say, “God is good” the word “good” means the same as it would if you said: “That man over there is good.” Others, including Thomas Aquinas, argued that such words when applied to God could only be analogies for anything that applied to human beings. Words applied to God are different, their meaning is different, because God is different. Scotus rejected this and held that such notions as goodness, power, reason, were “univocally” applicable. When the philosopher Gilles Deleuze developed the idea in the 1990s, he emphasised that far from endorsing conformity in this “univocity”, what the term actually signified was that the one characteristic of all being is difference. Things are different from other things. Or as the poet Charles Olson put it, paraphrasing Heraclitus, “What does not change / is the will to change.”

Scotus gave his last name to Scotism, essentially a method of learning which emphasises dialectical reason (thesis, antithesis, synthesis), inference and the acceptance and resolution of contradictions. His first name was used by his opponents to label people they deemed incapable of learning much at all: the “dunce’s cap” (an inverted cone) was used within living memory in schools where the practice was to stigmatise and shame less able scholars publicly. Without going deep into the details of religious philosophy in arguments that continued over centuries, or the ideas associated with what the philosopher Martin Heidegger called “onto-theology”, it’s enough to note here that modern thought from the 1960s on saw Scotus as moving away from the beliefs of Aquinas, and that the heart of this shift, in some complex respects, foreshadowed the division defined in Scotland in 1560 by the Reformation. The American Edward Dorn has a pertinent short poem called “The Protestant View” whose meaning is every bit as political as it is religious: That eternal dissent and the ravages of faction are preferable to the voluntary servitude of blind obedience.

You don’t have to agree with that preference to see what he means.

Then there were the Norse. The ravages of faction were most violent when the Norsemen came south, round the northern coast of Scotland and into the western islands. Iona was terrorised in 795, again in 802 and 806, and the following years most of the community left for Kells in Ireland (hence the name given to their most beautiful book).

A god who walked on water without getting his feet wet was no match for gods devoted to war, seafaring and cunning. Yet the stories and images that come down to us from both worlds are equally haunting. The crane, exhausted by flying through storms and violent winds, is nursed back to health by Columba. The ravens, blood-gorged in the Norse fields of slaughter, embody a different portent. One mythic world speaks of the creation and sustaining of peace and healing, the other of the necessity of sacrifice and the natural inevitability of violence. Both are contemporary, in their time and in ours.

The sagas tell stories of people who inhabited various places and moved around, from the Norse countries, through the northern seas, to island archipelagos, Orkney, Shetland, Faroe, north to Iceland and Greenland, west to America and south to the Hebrides and the Scottish mainland, west again to Dublin. One of the greatest of all, Njal’s Saga, written in Iceland around 1280, tells of its characters holding parts of Ross, Moray, Sutherland and Caithness (Njal is the Gaelic name Neil). Njal’s Saga is one of the great works of literature, with its evocation of a world where wrongs and grievances cross generations and no matter what efforts good people make to prevent the worst from happening, bad things befall people anyway. The burning of the house which Njal and his family are defending is one of the most horrific episodes. No one describes the darkness of the northern night as powerfully as the author of this saga.

The Norse presence in Scotland is extensive. The Orkneyinga Saga refers to Norse connections with Galloway, in south-west Scotland. The historian Alfred P. Smyth in his book War Lords and Holy Men (1989) wrote: “this Scottish tradition in Icelandic oral history is of far greater antiquity than the thirteenth-century saga age, and it was so strong that it survived for centuries”. Both Laxdaela Saga and Eyrbryggja Saga begin with accounts of the Hebridean origins in Scotland of the great families of the western fjords of Iceland: “a group of stubborn Vikings settled in the Hebrides” in the 860s and 870s. This genealogy was as important to its Icelandic audience “as the Book of Genesis was to the Hebrews”.

Certainly, for George Mackay Brown (1921-1996) in Orkney in the late 20th century, the significance of The Orkneyinga Saga (written in Iceland c1200) was undisputed. According to Mackay Brown, the two great undertakings of the “most intriguing character” in the saga, Rognvald Kolson, Earl of Orkney, were a crusade with fifteen ships to Jerusalem in 1151-54 and the building of Kirkwall Cathedral in honour of his uncle, St Magnus (begun in 1147). Magnus’s story haunted Kolson all his life. It also haunted Mackay Brown. He returns to the theme in numerous poems and most powerfully in his novel Magnus (1973), where the events of Magnus’s martyrdom are related to the violence of the Nazis during World War Two. The paradox of a good man, Magnus, being killed by his own brother, knowingly sacrificing himself to allow peace to reign free of rivalry and social contention is one of the most violent yet also Christian stories. In his earlier novel, Greenvoe (1972), Mackay Brown gets to the heart of this matter: And I would not have you think either that love is all sweet desire and gratification, and thereafter peace. The essence of love is pain; deep in the heart of love is a terrible wound. Yes, and though a man should grow wise and quiet at last, yet if he hath trafficked in love but once, he shall be borne to his grave with the stigma of suffering on him. His monument shall bleed.

There are unforgettably gruesome images from The Orkneyinga Saga, like the severed head of an enemy exacting its revenge upon the victorious warrior who was carrying it on horseback, tied to his saddle, by opening its mouth with the movements of the horse and gnawing with its teeth the warrior’s leg, giving him a wound which, seeming negligible, festers, suppurates and causes his death.

Before George Mackay Brown, another modern Orkney writer had been profoundly influenced by the sagas: Eric Linklater (1899-1974). In its very title, his first novel, White-Maa’s Saga (1929), makes the connection and in The Men of Ness (1932) and elsewhere, the mythic dimensions of the narratives and the personal qualities of characters, of courage, tenderness and an understanding of violence are important components of his work. This is vivid in the autobiographical episodes from World War One in the early chapters of Magnus Merriman (1934) and in the World War Two novel Private Angelo (1946). The struggle to find a way to build a life worth having in the 20th century, after bloody conflict and psychological trauma, is an epic effort in which Linklater’s writing draws as much valuable knowledge from his readings of the sagas and the Celtic myths, as from his own personal experience.

For a long time, the northern islands, Orkney and Shetland, and the Outer and Inner Hebrides in the western sea, were all identified with Scandinavian centres of authority rather than with the kingdom of Scotland. But the sea is an open road. In the second half of the first millennium it was as open as the skies have been in the second half of the second and beginning of the third: murderers, pirates, colonists and settlers arrive and go as they will with their different purposes.

Some things don’t change. Matter and mortality are our condition, however we might value the spirit. The Christian, pre-eminently Latin tradition, and the Norse sagas are both ancient forms of understanding the world. Both made deep contributions to the development of the literary and cultural vision to be found distinctively in Scotland.