Through the keyhole tells the story of public decency in France, using original analysis that blends architecture, literature and psychiatry. We discover how the law has long exerted control over sexuality by distributing the visible world between illegal and legal domains with regard to certain behaviours, transforming real spaces into institutional and political spaces. In 1857, a group of young people who had participated in an orgy in a private mansion were sentenced for contempt of public decency (outrage public à la pudeur), because a voyeur was able to watch them through a keyhole. In 1893, students who organised the Quat'z'Arts ball declared a 'war of the nude' against the courts by demanding that certain forms of public nudity be considered chaste. In the 1960s, a passionate public debate ensued on whether women bathing topless on French beaches constituted indecent exposure. The crux of each of these debates hinges on where the public ends and the private begins; what one can reveal and what one ought to hide. Today, the term pudeur has disappeared from the French penal code to be replaced by Sex. But, far from being an epic story of hard-won freedom, this book demonstrates that the transformation techniques used by the French State in the last two centuries have rendered sexuality into a spectacle and have conditioned our spaces, clothes, comportment and even some of our mental illnesses. This politico-legal history will appeal to students and scholars of gender and sexuality studies, legal history, French studies and sociology.