This article offers a novel interpretation of Karl Popper’s influential yet controversial book, The Open Society and Its Enemies (1945). Popper, it argues, sheds light on a pivotal social and political question: How can we value genuine human plurality without succumbing to the illusion that enmity can be removed from the socio-political realm? What we find in Popper, I argue, is an “anti-utopian agonism,” that is, his conception of an open society harbors significant agonistic elements—a commitment to human plurality, an (...) endorsement of (some) social and political struggles, and an acute awareness of the tragic dimensions of political life. Simultaneously, Popper’s distinctive anti-utopianism makes an important contribution to agonistic theory on two fronts. First, his concept of “the strain of civilization” reveals a deeper notion of tragedy, which gives him the edge over the rather shallow notion of tragedy we find in the agonistic tradition. Secondly, he develops a tripartite notion of enmity, which is theoretically interesting and practically relevant. The aim of this article is not only to contribute to the scholarship on Popper and agonism but, first and foremost, to demonstrate how The Open Society still matters as an inspiring work that illuminates the practically relevant question of how to value diversity without illusions. (shrink)