This article investigates the way the notion of constraint could be extended to theater studies and theater history, focusing on the case of French classical tragedy in the seventeenth century. Can classical poetics be regarded as a set of constraints? Rather than viewing the constraint as a literary technique, the authors argue that it is also relevant to other, nonliterary phenomena, for example, to the theater. There the idea of constraint can be put to use as a tool for theoretical reflection on and critical or historical analysis of performance practice. The article pays special attention to (1) the way Aristotelian poetics developed throughout the seventeenth century from a flexible set of tips to a hegemonic theoretical practice; (2) the increasing use of textual and performative constraints to resolve the disorder and friction typical of French (early) modern theater practice; (3) the divergence between theory and practice, between the intended and the actual performance; and (4) the relationship between the notion of constraint, on the one hand, and that of discipline, on the other.