O'Brien had read Fanon earlier and more closely than most of those who invoke him. States of Ireland (Hutchinson, 1972) includes a biting critique of Fanoniste criteria as inflicted upon the Emerald Isle. His range of literary reference was wide and unpredictable: on another occasion he wrote a mordant open letter in Harper's in 1981 to four prominent US Senators, telling them that if they actually got the reunited Ireland they claimed to desire, they would be in the position of the bereaved parents in the ghost story The Monkey's Paw, who summon up their dead son after a ghastly factory accident, but fail to stipulate that he be alive and whole when he appears. He was a major intellectual by international as well as Irish standards, whose work on a variety of literary and political subjects (Burke, Yeats, Catholic novelists) will endure. But unlike most intellectuals, he possessed a mastery of contemptuous rhetorical style in his journalism akin to H.L. Mencken's.

This, with his huge curiosity about politics worldwide and his penchant for slicing down with Occam's razor, could lead to over-reaction. His endorsement of Israeli policy in The Siege (Simon & Schuster, 1986) owed much to the equivalence he perceived between the PLO and the IRA, and does not look prescient nowadays - though his writings on South Africa pre-Mandela were farsighted and realistic, as is the case with much of his work on Africa, which he knew well. The weight and range of his critical, political and historical essays cannot be addressed here. But his ability to raise awkward questions in criticism as in politics was early demonstrated in his 1965 essay on Yeats's sympathies with fascism, Passion and Cunning. The critic Terence de Vere White remarked that he read it in such a rage that "the print swam before my eyes". It has provoked a large secondary literature, and continues in many respects to hold the field. More obtuse commentators have failed to attend to O'Brien's emphasis on the intermittent nature of all of Yeats's political activity, or to contextualise the poet's position as sensitively as O'Brien. But the essay is at once suavely insinuating and brazenly offensive, in his characteristic mode:

"During Yeats's life, the English Government gave him a Civil List pension, and the Athenaeum Club the signal honour of a special election. Since his death, the British Council has presented him to the world as one of England's glories. There is therefore some irony in the thought that there was something in him that would have taken considerable pleasure - though not without a respectful backward glance at Shakespeare - in seeing England occupied by the Nazis, the Royal Family exiled, and the Mother of Parliaments torn down. Meanwhile in Ireland, one would have expected to see him at least a curious participant, or ornament, in a collaborationist regime."

The print swims a bit, even now. Passion and Cunning was written before the North blew up but rereading it one can trace the lineaments of the saeva indignatio, and the eye for exposing the less attractive side of Irish nationalist commitment and instinctual Anglophobia that would produce States of Ireland seven years later.