This paper argues that practice, not science, decides the performativity of science. The argument is inspired by Austin's question of what it is that gives language its performative force. What are the conditions which connect sentences to certain effects? Advancing this question from the level of sentences to a societal level, and taking inspiration from the failure of Marxist notions of the relation between theory and practice, the paper suggests thinking critical performativity under the

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... itions of differentiation. This idea is qualified by means of Niklas Luhmann and his theory of a functionally differentiated -or polycontextural -society. Functional differentiation and polycontexturality mean that systems cannot communicate with each other; there is no real transfer of scientific knowledge into practice. Unhappy performativity is the rule. Based on this insight the paper discusses elements of a critical research strategy -under polycontextural conditions -and four guidelines for a critical science are suggested.