Abstract: In 1888, the colonial governments of Australia came together to agree on a policy of racial exclusion — aimed at preventing Chinese immigration. This article argues that key figures in the colonial ruling class feared the development of a racially divided population and shows them drawing on the mainstream liberal theory of anti-slavery, and John Stuart Mill’s theory that representative government required social homogeneity, to construct and legitimise their position. While anti-slavery has long passed as a major element in public policy, Mill’s argument for homogeneity shaped Australian justifications for White Australia through much of the twentieth century and, arguably, still informs elements of contemporary immigration policy.