POET, POLEMICIST, social conscience, humanitarian, Jonathan Swift is Ireland's Goethe. When considering the legacy of Yeats, one must look to Swift; Yeats certainly did.

Born in Dublin in 1667 to English parents, Swift, a cousin of the poet Dryden, was a most reluctant Irishman. The ironies are manifold; his political ambitions were focussed on England and he was to see Ireland as a place of exile. Yet he remains a defining and essential presence in Irish literature.

If there is a central element to his genius it could be his own cultural insecurity. There is also his aggression which made his writing so urgent, so alive. And of course, there is his famous indignation and his flair for the grotesque, the fantastic. If may seem far-fetched, but if one examines the work of another Irish comic genius, Dave Allen, that inspired use of comic exasperation is traceable to Swift. The manic eloquence that fuels Dylan Moran and Graham Linehan's ingenious Channel 4 series, Black Books, is in fact Swiftian.

As a young man, Swift had been well placed for a political career in London. Educated at Kilkenny College, and later at Trinity, he then joined the household of Sir William Temple, who sent him to William III's court on business. While waiting for his political break, he was ordained. At Temple's home, Moor Park, he met Esther Johnson, "Stella".

He wrote The Battle of the Books (published later, in 1704), in which modern works decide it is time for the classics to withdraw. Meanwhile, a spider and a bee also, Aesop-like, begin their own dispute which reflects the literary clash of the old and the new.

Temple died in 1699 and Swift returned to Ireland and began his connection with St Patrick's. Travelling between Dublin and London, he became part of the London literary scene and nursed his political ambitions which would die with the death of Queen Anne in 1714 when the Tory ministry also collapsed. Some years earlier, however, a second Esther, Esther Vanhomrigh, "Vanessa", entered his life. She loved him so intensely that she followed him to Ireland. Though suffering from TB, her death in 1723 may have been caused by his breaking off their friendship. She was always jealous of "Stella" to whom he wrote his Journal to Stella, and who may have been his muse. She died in 1728.

His body of writing is both immense and varied: from major political publications on British politics to his important pamphlets such as A Modest Proposal and Drapier's Letters in 1724 which foiled a plan to impose a copper currency, "Wood's Halfpence" on the Irish.

Gulliver's Travels dominates his reputation but he was a prolific classical poet and moved easily between the polemic, satirical and poetic. The life is big, the man a giant and for a while, he was also an important political figure, but the literary legacy is astonishing and often underplayed.

A complex final illness, possibly the advanced stages of Ménière's Disease from which he suffered throughout his life, affected his balance and created the myth that the dean of St Patrick's had succumbed to madness. Swift was never insane, just consistently outraged.