W B Yeats was a tough prophet for our times

W B Yeats at 150 somehow seems more alive than any other English-speaking poet of the last two centuries. He is no member of the Dead Poets' Society; his pulse is stronger than that of many poets whose hearts are still beating.

A part of this can be attributed to Yeats's Irish identity – to his role in laying the cultural foundations for a new nation. Not many poets have helped to found what are in effect national theatres (the Abbey Theatre in Dublin) or served as senators (here Pablo Neruda comes to mind). Yeats is certainly one of the most important figures in Irish cultural history – and a member of one of Ireland's most distinguished artistic families: his brother Jack Yeats holds a comparable position in Irish painting. But he is much more than that.

Yeats is alive mainly because so many of his lines seem extraordinarily prescient and as pertinent to our times as to his. The prophetic verses of The Second Coming – "Things fall apart, the centre cannot hold/ Mere anarchy is loosed upon the world" – have been invoked time and again but do not lose their power. Trying to frame a response to the imminent destruction by Islamic State of the ancient city of Palmyra in Syria, I recalled the opening lines of one of Yeats's darkest meditations, 1919, written as Ireland was tearing itself apart: "Many ingenious lovely things are gone/That seemed sheer miracle to the multitude."

Yeats died just before the catastrophe of the Second World War but his poetry seems able to encompass and face up to the most destructive century in human memory. Its way of doing so is idiosyncratic in the extreme, relying more on Irish and Greek myth, mystical and antinomian texts by Plotinus, Blake, Swedenborg, Nietzsche and Madame Blavatsky than on the approved masters of 19th- and 20th-century scientific, political and economic thought. Yeats turned himself from a wistful romantic into a tough-minded prophet – a unique metamorphosis at least in poetic history that makes him the bridge between two centuries or between late romanticism and modernism.

This shift was partly achieved at the purely poetic levels of rhetoric, prosody and imagery: Yeats made his language harder-edged and his rhythms and sound-effects more abrupt, less dreamy. But it also involved a deep personal transformation. He moved from a private introverted world of unrequited love expressed in Celtic Twilight imagery into full engagement with the public and political world of civil war, nation-building and international convulsion. But in Yeats the personal and political always intertwine at the most visceral levels.

One of his most profound and pertinent themes is his attempt to understand and go beyond fanaticism. He had to understand fanaticism because he fell hopelessly in love with a fanatic, the militant Republican zealot Maud Gonne, who later married one of the leaders of the 1916 Easter Uprising. He even recognised his own "fanatic heart". In his great poem Easter 1916 Yeats pays ambivalent tribute to those who took part in the armed Republican insurrection (15 of the leaders were executed by the British): he wrote that "a terrible beauty is born" but at the same time he questioned their intransigence: "Too long a sacrifice/Can make a stone of the heart."

Yeats worried about effects of ideology and theory on the human heart, its capacity for empathy and joy. He saw this danger in Ireland – "Great hatred, little room/Maimed us at the start" – but his insight is equally relevant to the conflicts of the 20th and 21st centuries.

Above all Yeats asked these questions: How do we cope with the end of civilisation – or at least with the destruction that accompanies the end of one epoch and the start of another? At the same time how do we confront our own inevitable ageing, decline and death? Yeats's response in his unbuttoned, sometimes shocking late poems has thrilling, defiant energy. "You think it horrible that lust and rage/Should dance attendance upon my old age?... What else have I to spur me into song?" That is why he is still so alive so long after he died, still seeking rejuvenation, in the south of France in that fateful summer of 1939.