In 1955, Paris Police Commissioner Guy Isnard curated the exhibition Le Faux dans l'art et dans l'histoire at the Grand Palais in Paris. Featuring a wide variety of forgeries, most notably counterfeit sculptures and paintings, the exhibition was an occasion to showcase the anti-counterfeiting efforts of the National Police. But in the broader context of the politically and economically weakened Fourth Republic, more was at stake. In the immediate postwar period, French society was steeped in uncertainty and a growing fear of inauthenticity, fueled by rumors of currency manipulation by foreign powers, the perceived corruption of the French language by an increasingly influential English, and anti-Americanism in intellectual and political circles. In this environment, the organizers of the exhibition called upon culture, and art in particular, to reaffirm a strict distinction between truth and falsity while also establishing France as the uncontested guardian of truth. This essay shows that Le Faux dans l'art et dans l'histoire constituted a crucial threshold moment in twentieth-century French history, both as an attempt to preserve a rapidly fading vision of truth and originality and as a prefiguration of aesthetic and philosophical debates to come.