This article considers the ways in which White South African holidaymakers justify racial segregation and criticize social transformation by explaining segregation as the natural and hence inevitable outcome of the ‘fact’ that humans are cultural beings. By investigating the ontological features of the racial discourse, we draw attention to the way in which ordinary people use universal theories about humans – as cultural beings – to naturalize racist practices. The rhetorical force of the arguments was derived from a scientific way of thinking. They were universalising and objectifying, and were arranged to disconfirm plausible rival hypotheses. The arguments functioned ideologically to defend segregation and criticize social transformation in South Africa, which they did by placing ontological limits on ‘what is’ and ‘what is possible’ regarding cultural contact. The paper concludes by suggesting that cultural and biological discourse of ‘race’ share common rhetorical and ideological strategies and functions.