William Grimes in the NYT:
Mr. O’Brien, once described by Christopher Hitchens as “an internationalist, a wit, a polymath and a provocateur,” was a rare combination of scholar and public servant who applied his erudition and stylish pen to a long list of causes, some hopeless, others made less so by his combative reasoning. When called upon, he would put down his pen and enter the fray, more often than not emerging bruised and bloodied.
As a diplomat, he helped chart Ireland’s course as an independent, anticolonialist voice in the United Nations and played a critical role in the UN’s intervention in the Congo in 1961. As vice-chancellor of the University of Ghana he fell out with the dictator Kwame Nkrumah over the question of academic freedom, and while teaching at New York University, he took part in an antiwar demonstration that resulted in his arrest.