Early in the twentieth century, American philosopher and educator Horace M. Kallen (1882–1974) constructed a cultural philosophy under the headline Cultural Pluralism. This philosophy was intended to have cosmopolitan effects in the sense that it had global ecumenical concerns for the social hope for all. Nevertheless, Kallen avoided the concept of cosmopolitanism because of the deep controversy over Jews and Jewishness entangled in the history of cosmopolitan thought since the Enlightenment. As an alternative, Kallen re-invented a new Jewish past to suit a future when Jewishness could be a model attitude for living in cosmopolis. This article shows how and why cosmopolitanism has been a problematic idea for Jewish thinkers such as Kallen, and it demonstrates how Kallen’s early-twentieth-century ideas of Cultural Pluralism in many ways constitute a postcolonial cosmopolitanism avant la lettre.