His early work tended towards romantic lushness best described by the title of his 1893 collection The Celtic Twilight, but in his 40s, inspired by his relationships with modernist poets such as Ezra Pound and his involvement in Irish nationalist politics, he moved towards a harder, more modern style. Yeats also served as an Irish Senator.

He was awarded the Nobel Prize for literature in 1923 for what the Nobel Committee described as "his always inspired poetry, which in a highly artistic form gives expression to the spirit of a whole nation".

When Yeats was young, his family moved first from Sandymount, County Dublin, to County Sligo, and then to London to enable his father John to further his career as an artist. At first, the Yeats children were educated at home. Their mother, who was homesick for Sligo, entertained them with stories and folktales from her native county.

In 1877, William entered the Godolphin school, which he attended for four years. He did not distinguish himself academically. For financial reasons, the family returned to Dublin towards the end of 1880, living at first in the city centre and later in the suburb of Howth.

In October, 1881, Yeats resumed his education at the Erasmus Smith High School in Dublin. His father's studio was located nearby and he spent a great deal of time there, meeting many of the city's artists and writers. He remained at the high school until December 1883.

It was during this period that he started writing poetry and in 1885, Yeats' first poems, as well as an essay called "The Poetry of Sir Samuel Ferguson", were published in the Dublin University Review. From 1884 to 1886, he attended the Metropolitan School of Art (now the National College of Art and Design) in Kildare Street.

Even before he began to write poetry, Yeats had come to associate poetry with religious ideas and thoughts of sentimental elements. Describing his childhood in later years, he described his "one unshakable belief" as "whatever of philosophy has been made poetry is alone... I thought... that if a powerful and benevolent spirit has shaped the destiny of this world, we can better discover that destiny from the words that have gathered up the heart's desire of the world."

Yeats' early poetry drew heavily on Irish myth and folklore and drew on the diction and coloring of pre-Raphaelite verse. His major influence in these years - and probably throughout the rest of his career as well - was Percy Bysshe Shelley. In a late essay on Shelley he wrote, "I have re-read Prometheus Unbound... and it seems to me to have an even more certain place than I had thought among the sacred books of the world."

Yeats' first significant poem was The Isle of Statues, a fantasy work that took Edmund Spenser for its poetic model. It appeared in Dublin University Review and was never republished. His first book publication was the pamphlet Mosada: A Dramatic Poem (1886), which had already appeared in the same journal, and this printing of 100 copies was paid for by his father. Following this was The Wanderings of Oisin and Other Poems (1889).

The long title poem, the first that he would not disown in his maturity, was based on the poems of the Fenian Cycle of Irish mythology. This poem, which took two years to complete, shows the influence of Ferguson and the Pre-Raphaelites. It introduced what was to become one of his most important themes: the appeal of the life of contemplation vs. the appeal of the life of action. After The Wanderings of Oisin, he never attempted another long poem. His other early poems are lyrics on the themes of love or mystical and esoteric subjects.

The Yeats family had returned to London in 1887, and in 1890 Yeats co-founded the Rhymer's Club with Ernest Rhys. This was a group of like-minded poets who met regularly and published anthologies in 1892 and 1894. Other early collections include Poems (1895), The Secret Rose (1897) and The Wind Among the Reeds (1899).

Maud Gonne, the Irish Literary Revival and the Abbey Theatre
In 1889, Yeats met Maud Gonne, a young heiress who was beginning to devote herself to the Irish nationalist movement. Gonne admired Yeats' early poem The Isle of Statues and sought out his acquaintance. Yeats developed an obsession with Gonne, and she was to have a significant effect on his poetry and his life ever after.

Two years after their initial meeting, Yeats proposed to her, but was rejected. He was to propose to Gonne a total of three more times: in 1899, 1900 and 1901. With each proposal, she rejected Yeats and finally, in 1903, married the Roman Catholic Irish nationalist John MacBride. This same year Yeats left for an extended stay in America on a lecture tour. His only other affair during this period was with an Olivia Shakespear, whom he met in 1896 and parted with one year later.

Also in 1896, he was introduced to Lady Gregory by their mutual friend Edward Martyn, and she encouraged Yeats' nationalism and convinced him to continue focusing on writing drama. Although he was influenced by French Symbolism, Yeats consciously focused on an identifiably Irish content and this inclination was reinforced by his involvement with a new generation of younger and emerging Irish authors.

Together with Lady Gregory and Martyn and other writers including J M Synge, Sean O'Casey, and Padraic Colum, Yeats was one of those responsible for the establishment of the literary movement known as the Irish Literary Revival (otherwise known as the Celtic Revival).

Apart from these creative writers, much of the impetus for the Revival came from the work of scholarly translators who were aiding in the discovery of both the ancient sagas and Ossianic poetry and the more recent folk song tradition in Irish. One of the most significant of these was Douglas Hyde, later the first President of Ireland, whose Love Songs of Connacht was widely admired.

One of the enduring achievements of the Revival was the setting up of the Abbey Theatre. In 1899 Yeats, Lady Gregory, Martyn and George Moore founded the Irish Literary Theatre. This survived for about two years but was not successful. However, working together with two Irish brothers with theatrical experience named William and Frank Fay and Yeats' unpaid-yet-independently wealthy secretary Annie Elizabeth Fredericka Horniman (a wealthy Englishwoman who had previously been involved in the presentation of George Bernard Shaw's Arms and the Man in London in 1894) the group established the Irish National Theatre Society.

This group of founders was also able, along with J M Synge, to acquire property in Dublin and open the Abbey Theatre on 27 December 1904. Yeats' play Cathleen Ni Houlihan and Lady Gregory's Spreading the News were featured on the opening night. Yeats continued to be involved with the Abbey up to his death, both as a member of the board and a prolific playwright.

In 1902, Yeats helped set up the Dun Emer Press to publish work by writers associated with the Revival. This became the Cuala Press in 1904. From then until its closure in 1946, the press, which was run by the poet's sisters, produced over 70 titles, 48 of them books by Yeats himself. Yeats spent the summer of 1917 with Maud Gonne, and proposed to Gonne's daughter, Iseult, but was rejected.

In September, he proposed to Georgie Hyde-Lees, was accepted, and the two were married on 20 October. Their marriage was successful, though she was twenty-six and he was fifty-two at the time. Around this time he also bought Ballylee Castle, near Coole Park, and promptly renamed it Thoor Ballylee. It was his summer home for much of the rest of his life.

Mysticism
Yeats had a life-long interest in mysticism, spiritualism, and astrology. In 1885, he and friends formed the Dublin Hermetic Order. This society held its first meeting on June 16, with Yeats in the chair. The same year, the Dublin Theosophical lodge was opened with the involvement of Brahmin Mohini Chatterjee.

Yeats attended his first séance the following year. Later, Yeats became heavily involved with hermeticist and theosophical beliefs, and in 1900 he became head of the Hermetic Order of the Golden Dawn, which he had joined in 1889. After his marriage, he and his wife dabbled with a form of automatic writing, Mrs. Yeats contacting a spirit guide she called "Leo Africanus."

Yeats' mystical inclinations, informed by Hindu religion (Yeats translated The Ten Principal Upanishads (1938) with Shri Purohit Swami), theosophical beliefs and the occult, formed much of the basis of his late poetry, which some critics attacked as lacking intellectual or philosophical insights.

Modernism
In 1913, Yeats met American poet Ezra Pound. Pound traveled to London to meet the older man, whom he considered "the only poet worthy of serious study". From that year until 1916, the two men wintered in the Stone Cottage at Ashdown Forest, with Pound nominally acting as Yeats' secretary. The relationship got off to a rocky start when Pound arranged for the publication in the magazine Poetry of some of Yeats' verse with Pound's own unauthorized alterations.

These changes reflected Pound's distaste for Victorian prosody. In particular, the scholarship on Japanese Noh plays that Pound had obtained from Ernest Fenollosa's widow provided Yeats with a model for the aristocratic drama he intended to write. The first of his plays modeled on Noh was At the Hawk's Well, the first draft of which he dictated to Pound in January 1916.

Yeats is generally considered to be one of the twentieth century's key English-language poets. Yet, unlike most modernists who experimented with free verse, Yeats was a master of the traditional verse forms. The impact of modernism on Yeats' work can be seen in the increasing abandonment of the more conventionally poetic diction of his early work in favour of the more austere language and more direct approach to his themes that increasingly characterises the poetry and plays of his middle period, comprising the volumes In the Seven Woods, Responsibilities, and The Green Helmet.

Politics
The poetry of W.B. Yeats' middle period moved away from the Celtic Twilight mood of the earlier work. His political concerns moved away from cultural politics. In his early work, Yeats' aristocratic pose led to an idealisation of the Irish peasant and a willingness to ignore poverty and suffering. However, the emergence of a revolutionary movement from the ranks of the urban Catholic lower-middle class made him reassess his attitudes.

Yeats' new direct engagement with politics can be seen in the poem September 1913, with its well-known refrain "Romantic Ireland's dead and gone,/It's with O'Leary in the grave." This poem is an attack on the Dublin employers who were involved in the famous 1913 lockout of workers who supported James Larkin's attempts to organise the Irish labour movement. In Easter 1916, with its equally famous refrain "All changed, changed utterly:/A terrible beauty is born", Yeats faces his own failure to recognise the merits of the leaders of the Easter Rising because of their humble backgrounds and lives.

Yeats was appointed to the Irish Senate (Seanad Éireann) in 1922 and one of his main achievements as a Senator was to chair the coinage committee that was charged with selecting a set of designs for the first coinage for the Irish Free State (and the costumes of Irish judges!). He also spoke against proposed anti-divorce legislation in 1925. His own characterisation of himself as a public figure is captured in the line "A sixty-year-old smiling public man" in the 1927 poem "Among School Children". He retired from the Seanad in 1928 because of ill health.

During his time as a senator Yeats warned his colleagues "If you show that this country, southern Ireland, is going to be governed by Roman Catholic ideas and by Catholic ideas alone, you will never get the North … You will put a wedge in the midst of this nation". As they were virtually all Catholics, they were offended by these comments.

Yeats' essentially aristocratic attitudes and his association with Pound tended to draw him towards Mussolini, for whom he expressed admiration on a number of occasions. He also wrote some 'marching songs' (which were never used) for General Eoin O'Duffy's 'Blueshirts', a quasi-fascist political movement. However, when Pablo Neruda invited him to visit Madrid in 1937, Yeats responded with a letter supporting the Republic against Fascism. Yeats' politics are ambiguous: no friend of the Left (or democracy), he distanced himself from Nazism and Fascism in the last few years of his life. He was involved in the eugenics movement.

Later life and work
In his later poetry and plays, Yeats wrote in a more personal vein. His subjects included his son and daughter and the experience of growing old. Yeats himself, in the poem "The Circus Animals' Desertion", published in his final collection, describes the inspiration for these late works in the lines "Now that my ladder's gone,/I must lie down where all the ladders start/In the foul rag and bone shop of the heart".

In 1929, he stayed at Thoor Ballylee for the last time. Much of the remainder of his life was outside Ireland, but he did lease a house, Riversdale in the Dublin suburb of Rathfarnham from 1932. He wrote prolifically through the final years of his life, publishing poetry, plays and prose. In 1938, he attended the Abbey for the last time to see the premier of his play Purgatory. The Autobiographies of William Butler Yeats was published that same year.

After suffering from a variety of illnesses for a number of years, Yeats died at the Hôtel Idéal Séjour, in Menton, France on 28 January 1939, aged 73. The last poem he wrote was the Arthurian-themed The Black Tower.

Soon afterward, Yeats was first buried at Roquebrune, until, in accordance with his final wish, his body was moved to Drumecliff, County Sligo in September, 1948, on the corvette Irish Macha. His grave is a famous attraction in Sligo. His epitaph, which is the final line from one of his last poems, Under Ben Bulben is "Cast a cold eye on life, on death; horseman, pass by!" Of this location, Yeats said, "the place that has really influenced my life most is Sligo." The town is also home to a statue and memorial building in Yeats' honor.