This paper has a local, a general and a methodological ambition. We deal with a specific story, that of Geneva, the «Calvinist Rome», which was obliged in the first half of the nineteenth century to open its doors to the others, especially to the secular enemies who took the form of Catholic immigrants. Using implicative graphs we discover that the protestant religion remained the dominant structuring principle. While relatively stable protestant socioeconomic groups competed for power, Catholics did not take part in these struggles but grew demographically, remaining as invisible as possible.