Bernard of Clairvaux's engagement in the struggle against heresy in the 12th century has so far been understood as a logical result of his ecclesiology. In his effort to defend the unity of Christianity, the abbot fought against heresy, as, for him, it represented a major threat to the Church. However, the reverse question of what Bernard's anti-heretical writing brings to the understanding of his ecclesiology has remained almost entirely unexplored, despite the importance of these polemical writings for the "discovery" of Bernard. This article seeks to fill this gap by placing Bernard's anti-heretical discourse at the centre of inquiry in order to understand a crucial aspect of his ecclesiology and to follow how this ecclesiology was realized through specific means against heresy, these functioning as disciplinary practices. Using the theoretical works of Michel Foucault and Talal Asad and insights of modern sociology, the goal is to examine both the way in which the means against heresy operated and the logic behind them. In this way, the article demonstrates the process through which a discourse is articulated and imposed on society and, at the same time, through which a specific subjectivity is shaped and regulated.