This thesis examines the major stages in the political career of Oswald Mosley and argues that a continuity existed in his diagnosis of contemporary history from the moment he entered political life at the end of the First World War as a zealous parliamentarian till his last days as an unrepentant fascist. An ideal type of the 'esoteric' core of Mosley's ideology is used to identify a consistent thread which resolves the contradictions in Mosley's political agitations into paradoxes. Drawing on a theory of ideology which distinguishes between its fundamental and operative dimensions, Mosley's core (fundamental) ideology is depicted ideal typically as the ambition to realize Bntain's potential for national greatness conceived in a future oriented, modernizing rather than a nostalgic or conservative perspective. The structure of the biography follows the chronological narrative of Mosley's life, episodically, illuminating it through pivotal moments in his career. Through a textual and contextual analysis of these moments it identifies the performance of the operative dimension of Mosley's fundamental ideology in order to bring out its internal consistency. Each chapter highlights a theme which may have manifested itself at other moments in Nlosley's life but is especially distinct at one stage of Nlosley's career. These themes are the myth of the airman, leadership, economics, unemployment, the New Party, the nation and Greater Britain, anti-Semitism and violence, philosophical idealism and the philosophy of apologia. The thesis draws on the vast published textual output from Mosley along with reports of his speeches, supported by many contemporary writings relating to chapter topic. These resources are used to demonstrate and shed light on the esoteric mainspring of Mosley's politics. In addition the thesis demonstrates and argues in favour of a biographic methodology which does not construct the inner machinations of the subject's psychology or 'mind' as an explanation of behaviour but looks pragmatically to the significant products of the subject and constructs, ideal typically, a consistent ideological matrix the centre of the subjects politics. This thesis contributes to knowledge of the subject by presenting a pragmatic understanding of Mosley's political motivations and identifying a consistent core to his political pronouncements. The thesis also brings to biographical studies a phenomenological methodology which dispenses with the postulation of a knowable core personality or 'real' psychological life in order to demonstrate the inner coherence of the subject's personality for the purpose of historical reconstruction.