This thesis is a study on the ‘public intellectual’ in mid-twentieth century Ireland, where the figure of the intellectual in politics was routinely maligned or altogether rejected by a broad cross-section of civil society for being insufficiently deferential to societal norms and out of touch with the ‘real world’. It focuses on a major case study, Conor Cruise O’Brien (1917-2008), who, at the peak of his powers, achieved and maintained a remarkably high public profile. His books had a wide readership, his lectures drew sizeable audiences, and his public performances were widely covered in the Irish and international media. Based on the empirical analysis provided by a wide range of printed and manuscript sources, and by employing concepts and methods drawn from sociology and literary criticism, this thesis analyses Cruise O’Brien’s self-making as an intellectual, the construction of his public persona, what he had to say about society, and the media through which he intervened in public debate. The main argument is that his ‘positioning’ as a ‘courageous’ figure helped to provide him with opportunities to intervene in public affairs and establish a significant reputation not only in Ireland, but also in Great Britain and the United States. In Ireland, Cruise O’Brien turned himself into the standard bearer of liberalism at a time when the country was on the cusp of deep social and cultural changes. This thesis revises existing accounts of his life and work, substituting a more historically grounded interpretation of his rise to public intellectual status, his ideas about historical objectivity and politics, his thinking about the role of intellectuals in public debate, the relationship between aesthetics and political action, and his use of the rhetoric of disease to construct an image of public intellectuals as doctors to the body politic. The pattern of his activity showed his determination to perform the role of the public intellectual. By opting for passionate engagement with contemporary political events, such as the Cold War and the Northern Irish Troubles, as opposed to the safety of the so-called ‘ivory tower’, Cruise O’Brien consistently earned the label ‘courageous’, feeding into his own self-positioning and supplementing his ‘brand’.