In Australian Aboriginal affairs, the acculturative strand of assimilation developed in large part from Elkin’s religious and Idealist commitment, for which in the years 1928 to 1933 he won social-scientific authority. In competition with both an eliminationist politics of race and a segregationist politics of territory, Elkin drew upon religious experience, apologetics, sociology, and networks to establish a ‘positive policy’ as an enduring ideal in Aboriginal affairs. His leadership of the 1930s reform movement began within the Anglican Church, became national through civic-religious organs of publicity, and gained scientific authority as Elkin made religious themes a central concern in Australian anthropology. But from the 1960s until recently, most scholars have lost sight of the centrality of Idealism and religion in our protagonist’s seminal project of acculturative assimilation. This thesis aims to show how Elkin dealt with problems fundamental to twentieth century Aboriginal affairs and indeed to Australian modernity more generally – problems of faith and science, morality and expediency – in developing his positive policy towards Aborigines.