This article takes issue with Chantal Mouffe’s concept of "agonistic pluralism." With this concept, Mouffe brings political theory to the field of "real politics." In planning theory, the concept of agonism has recently been used as an alternative to the consensual communicative deliberative approach: The notion of agonism seems to be fit for replacing communicative theory as the theoretical framework of planning theory. My point is that Mouffe’s proposed "agonistic pluralism" has an internal and fundamental flaw and that the advocated "taming of antagonism into agonism" is neither possible nor necessary. To clarify my hypothesis, I consider in a first step the roots of Mouffe’s theory: Carl Schmitt’s notion of the political and his (in)famous friend/enemy concept. Schmitt’s model is not only a main reference of Mouffe’s work but the very reason of her calling for pluralistic agonism. In a second step, I turn to Ernesto Laclau’s political theory where another version of antagonism model appears: the conceptualization of the "constitutive outside" as irreducible reason of an endless hegemonic play of antagonistic forces. I show the difference between Schmitt’s and Laclau’s models and argue that the rationale for a conceptualization of agonism disappears with the latter. In my conclusion, I discuss whether and how antagonism theory can be linked with planning theory without importing Mouffe’s short circuit.