Despite its numerous critics, the notion of « Judeo-Christian tradition » is still commonly used in the public debate accross Europe and the United States. This study challenges a commonplace narrative in the Anglo-American world that sees this expression as a mere slogan born in reaction to fascism during the interwar period, and then to communism in the context of the Cold War and the aftermath of the Holocaust, or to the « Muslim world » for the advocates of a so-called « clash of civilizations » over the last decades. In Europe, the genesis of the « Judeo-Christian tradition » is instead entangled with the specific process of secularization of Postrevolutionary France.