Agreements about reciprocal recognition of patent rights between nations were at the heart of discussions at the International Union for the Protection of Industrial Property held in Paris in 1883. Yet while some treat the so-called “Paris Union” as a starting point for the subsequent globalization in patent rights, the context of early attempts at patent law harmonization was international tension and disagreements. Divergences in patent laws have their roots in the strong heterogeneity manifest among national patent systems developing before 1883. The sheer diversity of patent systems available was indeed highlighted by those critics who sought the abolition of patents rights. The project of harmonization should thus be seen as a defensive response to critics of patenting per se, rather than as the advent of a natural process of legislative convergence. In looking at the 1883 Convention in this light, we see that negotiations there can only be understood in terms of a strong rivalry between the French and German models. Such rivalries continued to characterize the membership of the Paris Union even into the interwar period, raising major doubts about whether the project of harmonization could ever be completed.