THE Celtic Revival of the late 19th century, so often disparaged as nostalgic and backward-looking, was in fact the precursor of the modern movement in Scotland. The Celts: Art and Identity exhibition, currently running at the National Gallery of Scotland in Edinburgh, shows us that the emphasis on skill and design and craftwork, central to the revival, led directly to the Celtic Modernism of the Glasgow Style in the work of Charles Rennie Mackintosh, Frances and Margaret MacDonald and Herbert McNair.

For The Four, as for many Scottish artists of the avant-garde, the stylised forms of Celtic art provided a pathway to Modernism. At the same time in Edinburgh, the Celtic Revival flourished under the inspirational leadership of the biologist and utopian visionary Patrick Geddes who commissioned male and female artist-designers such as Phoebe Traquair to undertake mural schemes, invited artists and scientists to his annual summer schoolsand encouraged Scottish and French artists and writers to contribute to his journal The Evergreen published in four volumes from 1895 to 1896. Geddes himself contributed an essay entitled The Celtic Renascence which had a huge influence on the young Hugh MacDiarmid.

In his book Modern Scottish Painting (1943), JD Fergusson says that the point about the modern movement in painting of around 1903-13, and especially the work of the cubists Picasso and Braque, was to acknowledge “the resemblances the average person finds in modern painting to ancient painting, I mean Stone Age and that sort of ancientness [...] When things are brought down or come down to fundamentals they do resemble each other in spite of many thousands or perhaps hundreds of thousands of years of time.”

Modern painting, or modernism in all the arts, “was an attempt to get back to fundamentals, and it succeeded [...] So there’s nothing out of order about really modern painting resembling really ancient painting, which was in its time of course really modern...” Fergusson’s magnificent Danu, Mother of the Gods uses the symbolism of the Celtic Revival to address a later, distinctly 20th-century world, and in his drawings and embellishments for MacDiarmid’s In Memoriam James Joyce (1955), Fergusson brings art, literature and music together in the ancient Celtic Ogham script, just as the poem sings praises of all forms of human creativity throughout time and across the world. When Fergusson was in Paris before the First World War, the city’s liberation of his imagination was surely partly due to the fact that he found himself among his fellow-Celts.

Revolutionary modernism for Scotland, as for elsewhere, entailed a revitalisation of rural and non-urban forms of language, social order and communal affiliation. Regenerating older traditions in the modern world was revolutionary in Scotland because it opposed the deadening hand of imperial hierarchy and the pretentiousness of cultural “sophistication”.

It returned the artistic elites to contact with the potential of people, generally, as surely and closely as JM Synge heard, internalised, and wrote in the idioms of rural Irish speech through his residences in Wicklow and the Aran islands, or as Jack Yeats saw, sketched and painted the people of Sligo and the west. Their art is no more naive than MacDiarmid’s or MacLean’s, and as advanced as that of Brecht or Munch.

The significance of this for us is that the artistic and political revolutions enacted in modernism in Ireland in the work of Synge, Joyce, Yeats, Sean O’Casey, Flann O’Brien and others, and in Scotland in the work of MacDiarmid, Lewis Grassic Gibbon, Neil Gunn, Nan Shepherd, Catherine Carswell, Willa and Edwin Muir and others, are, along with the political ideals of egalitarianism, self-determination and opposition to imperialism, all related in their attempts to get back to “the fundamentals”. Fergusson, like Picasso, is only as “advanced” as the work in the caves at Lascaux.

The fundamental thing about the Celts might be described as the matter of centralisation and goes back beyond Celtic Christianity. In his book, Scotland’s Music, John Purser observes that “it has never been in the nature of Celtic society to centralise” and that the Celtic church may be characterised by its distinctive “philosophy, organisation, language use, literary style” and other aspects of ecclesiastical practice that had adapted older, pre-Christian belief systems but were overtaken by the centralisation of the church in Rome.

To juxtapose that contentious episode with another equally contentious: the exhibition describes (with admirable and unusual clarity) the popularity of James Macpherson’s “Ossian” books and the hostility shown to them by Samuel Johnson. Johnson, compiling his English dictionary and establishing an authoritative language of cultural power that confirmed imperial superiority, was faced with an upstart Scot propounding a different tradition in the Celtic world going back before Latin.

In the wake of Culloden, Macpherson was stating in an immediately popular Enlightenment English that Gaelic Scotland was the cradle of an ancient civilisation as valid and deep as any and more so than most, certainly more so than that being ruled by the Hanoverian, only recently united, kingdom of Britain. No wonder Johnson hated him.

At one end of the spectrum of national identity we can find vanity (nothing could be better than us); at the other end, self-confidence. This self-confidence might be a fragile, vulnerable thing: we have to be able to take criticism. The anxieties that underlie vanity can be superseded by mature and sensitive self-confidence, an openness, opposed to the closed. Confidence doesn’t have to be arrogance. In other words, you neither cringe (we’re just not good enough), nor do you vaunt your ego (we’re incomparable, always right): rather, you think about it, seriously.

Maybe the lesson is that the best nation state would be one in which people were at ease with their own plurality, and open to revision, able to choose for themselves their own “elective affinities”. Arguably, this was made possible for us in the turn from the 19th to the 20th centuries, when readership, audience, public sensibility, began to fragment and diversify.

The work of Robert Louis Stevenson addresses local and international readers, children, travellers, colonials, imperialists, tribes of many kinds, just as printed work is becoming more widely available and commercialised interests are exploiting new readerships eagerly. The Celtic Revival contemporary with Stevenson is not really opposed to the rise of modernism: it runs into it, as Declan Kiberd reminds us in Ulysses and Us: The Art of Everyday Life in Joyce’s Masterpiece (2009).

And it resumes with new vigour after the Second World War: bloody revolutionary modernism led to political disasters but the arts show other ways. And in specific works by a range of writers, artists and composers, as the Celts exhibition shows brilliantly, this is evident through the engagement with Celtic myths and identities, from the old gods, through Cuchulain and the warrior cycle, to Ossian and tales of the Fianna.

The legacy evokes heroism, noble ideals, but pomp calls for satire and circumstance for subversion. Oliver Sheppard’s magnificent sculpture “The Dying Cuchulain” was moved to the General Post Office in Dublin in 1935 in preparation for the twentieth commemoration of the Easter rising, a solemn emblem. In 1938, in his poem “The Statues”, Yeats asks: “When Pearse summoned Cuchulain to his side, / What stalked through the Post Office?” He calls upon “We Irish”, born of “an ancient sect” but “thrown upon” a “filthy modern tide” to climb “to our proper dark” so that the beauty of “a plummet-measured face”, a (perhaps terrible) beauty arising from the depths of history, may be seen in full understanding.

The mysteries or ambiguities in these lines are multiple but there is surely commitment to both heroic aspiration and genuine humility. If there is nobility here, it is vulnerable. Samuel Beckett also invokes Cuchulain in Murphy (1957): the hero is now embodied in the statue in the Post Office, and the icon of self-sacrifice is the focus for the novel’s suicidal Neary, in a scene that could be described as radically iconoclastic comedy or hideous farce.

Old stories tell of Cuchulain learning the arts of war from Skathach, at Dunskaith, just off the Isle of Skye. This generates a different, fiercely feminist reading of not his but her story, centred in Scotland, in Janet Paisley’s novel Warrior Daughter (2009). The novel is a self-conscious validation of feminist priorities.

The point about all this is that the Celtic myths are durable because they can be used in so many ways.

From pre-Christian oral traditions, to the plantation of Ulster, to Irish immigration into early 20th-century Scotland, national identities are reciprocal, never wholly cut-off and defined. Thus the Scots language of Burns is shared and branches out among a whole school of Ulster poets. Joyce, preferring Finn and the outlaws (last minstrels, outsiders) rather than warrior-heroes like Yeats’s Cuchulain, prefigures MacDiarmid’s preference for the “Hjok-Finnie body” which he describes in the chapter “A Ride on a Neugle” in his magnificent “autobiography” Lucky Poet (1943).

Ossian the bard is most vivid to us today not only from Macpherson but in the visual arts, from the astonishing drawings and sketches of Alexander Runciman (1736-83) to the montage photographs of Calum Colvin, especially his “Blind Ossian” (2001). Celtic gods and warriors inhabit the symbolist, figurative art of John Duncan (1866-1945), with “The Fomors” and “The Riders of the Sidhe”. The recuperation of the Celtic myths in modernist work was, and is, triggered by the conjunction of abstraction and reality signalled across a century since Easter 1916.

As for connections in specific instances, think of these. In the visual arts in Scotland, the proto-impressionist Gaelic-speaking William McTaggart (1835-1910), in the 1890s, painted a series of major canvases on two major themes: the coming of Columba to Scotland from Ireland, and the leaving of Scotland by emigrants.

One theme portends regeneration, in spiritual, social, political reality, most evident in the greatest work ever to rise from what we might call a school of art: Iona’s Book of Kells. The other depicts immediate and recent catastrophe, and portends the politics of resistance the 20th century would bring, and this points forward to, for example, the outdoor sculptures of Will Maclean, commemorating the Clearances in Lewis and the western isles.

The exhibition begins with the eye-skinning wonder of Henry and Hornel’s gold-framed painting “The Druids: Bringing in the Mistletoe” (1890). If they ever saw this, Diaghelev and Stravinsky would have been delighted, if not envious. The fact that its portraits may owe something to the native Americans the artists may have seen in Buffalo Bill’s Wild West Show (1889) only adds to the contemporaneity of the vision. What history or science would describe as inauthentic, in the work of art becomes valid and speaks about things that are true.

In music, the ancient “Deirdre’s Farewell”, sung as she prepares to leave Scotland to return to Ireland, might contrast with “Fingal’s Cave” (1830) by Mendelssohn, celebrating his exhilarating arrival in a Scotland made new by international Romanticism. But then come forward to the American Amy Beach’s “Gaelic Symphony” (1894-96).

There’s no doubt about the British nationalism embodied by Boadicea on the Embankment, but Edward Elgar’s cantata “Caractacus” (1898) might suggest resistance to imperial domination rather than oppressions of imperial rule. Check it out.

And consider Arnold Bax’s Harp Quintet (1919) and Third Symphony (1928-29), written overlooking the white sands of Morar. And Granville Bantock’s “Celtic Symphony” (1940), scored for full orchestra and six harps, the most lavish and haunting of his numerous Celtic, Gaelic or Hebridean musical works.

Then come further forward to modernist Scottish composer Erik Chisholm (1904-65), and his “Ossian” Symphony No.2 (1939; recording 2007) (CDLX 7196), where the Celtic stories evoke opposing forces gathering in the rise of fascism in that decade; or his “Ossianic Lay” from “Preludes from the True Edge of the Great World” (1943, recording 2004) (DRD0223); or the dense and complex masterpiece, “Night Song of the Bards: Six Nocturnes for Piano” (1944-51; recording 1998) (OCD639). These are examples from classical music drawing on the shared Celtic myths with immense conviction and intensity, and infused with modern, contemporary political purpose.

One of the most breathtaking artefacts in the exhibition is the Carnyx, a horn instrument in the form of a long tube culminating in a boar’s head. Contemporary composers have allowed us to hear it in newly imagined ways n “The Voice of the Carnyx” CD (BML016) and John Purser’s “Bannockburn” (JWP030). There’s plenty more to track down but start with these.

In the closing lines of “On a Raised Beach” (from Stony Limits, 1934), MacDiarmid wrote this: “It is not more difficult in death than here / – Though slow as the stones the powers develop / To rise from the grave – to get a life worth having; / And in death – unlike life – we lose nothing that is truly ours.”

In other words, the struggle continues as perennially in humanity as the stony beaches move across geological time, and acknowledging mortality, we still try to achieve an independent, self-determined “life worth having” in defiance of all those forces trying to compel us to believe it could never be done.

“To rise from the grave – to get a life worth having” may be the imperative that gives preference to the connotations of a “rising” (as opposed to a “rebellion”) that applies in Scotland, or anywhere, as much as in Ireland. And it applies across Europe, in every national provenance, and cannot be relegated to history.

Go and study the Celts exhibition. Read widely. What is to be done?