For a long time, in so-called “developed” societies, “magico-traditional” practices such as shamanism, divination, and magnetism have been discredited, or even repressed, because of their supposed irreconcilability with the “modern” definition of science. In recent decades, however, these same practices have become increasingly tolerated. In some cases, they have even been promoted and protected by institutional actors. To explain this change of attitude, many authors have suggested a general cultural change. But this proposal does not take into account the transformations experienced by magico-traditional practices themselves in order to be “modernized.” It is precisely this modernization work that this article proposes to study on the basis of two empirical cases: magnetism in France and shamanism in Lambayeque (Peru). Using Ulrich Beck’s concepts of simple modernization and reflexive modernization and giving them an operational character within the framework of the field investigation, this article seeks to describe the effects, at times paradoxical, of the processes of legitimization of magico-traditional practices that their modernization makes possible. Often seen—according to the concept typical of simple modernity—as a “step backward,” these effects, from a sociological point of view, are shown to be linked to the deepening of the modern project.