Population change is hard to glimpse over days, weeks or even years. As such, immigration and differences in group birth rates often exert a muted effect on policy. Yet perceptions of demographic change shift much more quickly and readily break the political surface. Since 2002, immigration has consistently ranked among the British public’s leading concerns. Why? Mainly, both David Goodhart and Paul Collier argue, because immigration introduces cultural shifts that challenge the symbolic continuity of nations. Though both books criticise multiculturalism, one would expect a quieter tone from Collier than Goodhart. The latter, a former editor of Prospect and head of the think-tank Demos, is a well-known centre-left commentator on questions of immigration and national identity. His essay ‘Too Diverse?’ caused a storm of controversy in 2004 by arguing that increased diversity undercuts the cooperation needed for a strong welfare state. Collier, an impeccably liberal Oxford professor known for work on the political economy of development, has proposed, among other ideas, that material greed rather than ethnic attachments drives apparently ethnic civil wars. Given their backgrounds, it is astounding that the two arrive at the same terminus. In relation to his past work, Goodhart’s book comes across as conciliatory and academic, while Collier’s represents a radical break, stepping more brusquely onto sensitive ground.