Difference exists only with reference to another; in the case of the social sciences, this may be patriarchy, ‘whiteness’, ‘colour’, feminism, colonialism, or post-colonialism, all of which may be defined by what they are not. ‘The differentiation of an owning (capitalist) class from…the working class is foundational for capitalism in ways that gender, racial or sexual differences, however violent and life-destroying, are not’ (Malden (2008) PHG 31, 1, paraphrasing N. Castree and D. Gregory 2006). ‘Civil wars in Sri Lanka and sectarian fighting in Iraq are violent expressions of the difficulties of incorporating difference in the nation state’ (Staeheli (2008) PHG 32, 4). ‘Walls to limit the movement of people between two territories—whether between Israel and the Palestinian territories or between Mexico and the United States—suggest that difference may no longer be accommodated within the liberal state’ (Staeheli, op. cit.). I. Rivera-Bonilla (2000) analyses the way gating residential areas recreates spatial markers of class and racial differentiation. See also Valentine (2008) PPG 32, 3, 323.