Description: In Ernesto Laclau's political philosophy, identities (political subjects) are formed through the use of "empty signifiers". They are semiotic structures whose power to organise collective interests relies on their vagueness, or "undecidability". It makes it possible for various groups and subjects to invest their heterogeneous demands, and represent them by a common signifier. The paper intends to follow this idea in an analysis of educational theories and their role in political control. Laclau and Mouffe concentrate on the role of empty signifiers in mobilizing emancipatory (and - recently - also populist) political movements. My intention is to look at these rhetoric devices also as means of hegemonic political control. I will try to show that educational theorization may play a role in "emptying" certain common-language metaphors and concepts of their descriptive meaning, and - by way of utopian or "technological" concentration on the future - displacing them into the sphere of the unreal. So prepared, such concepts may then be used as tools of political control. An example here may be the displacement of the concept "life-long learning" - from the descriptive concept denoting a common phenomenon (we DO learn throughout all our lives) towards a utopian postulate of a new social order. Thus a certain discourse colonisation takes place, and educational thinking becomes an element of hegemonic practice. At the same time, however, educational theorising forms a horizon of radical critique and utopian hope. The paper will investigate this ambivalence on the basis of several historical and contemporary examples of educational theorizing. Methodology: Theoretical analysis, discourse analysis Conclusions: Critical reflection on the role of theoretical knowledge in education