Against the negative effects of urban segregation, many countries promote social mix within their urban policies. Yet much research question both the legitimacy and the benefits of these policies. This chapter presents a review of this research and the debates that accompany it. Two points are also considered to explain the discrepancy between academic critics and political discourses. First, while social mix policies may not always be appropriate to alleviate the negative effects of urban segregation, social mix may nevertheless be desirable from a philosophical perspective. Yet, normative considerations aside, this chapter reminds the reader how unevenly distributed the ability to make the most of social mix is. Second, the relative consensus around social mix helps to build support for social housing policies. The production of low-income housing raises many oppositions and contestations, and the relative consensus on social mix helps to overcome them.