This article examines the possibility of communication between human groups, including academic scientists addressing non-academics about topics they feel are important for all. This is a study of the effects of boundaries between human groups, and of potential resistance strategies to them. I show that the concrete knowledge anyone has of geographical borders applies to the boundaries created by the categorisations across human groups. Any power relationship leading to categorisation among humans leads to the creation of social frontiers: rich vs poor, heterosexuals vs non-heterosexuals, professors vs students, able-bodied vs disabled, men vs women, whites vs non-whites, centres vs peripheries, young vs old. These frontiers can be apprehended fundamentally like geopolitical borders. Approaching human categorisations from the angle of geopolitical borders has several advantages. First, it is an undeniably well-grounded parallel because geopolitical borders indeed create a categorisation among humans: maps are their most famously visualized manifestation. Second, the analogy is useful, because the spatial dimension of geopolitical borders makes them easier to grasp, compared to other types of human categorisations. Finally, this metaphor proves efficient for thinking change, by building a dynamic vision of power relationships and categorisations. The paper is organized into three parts. In the first part, I argue for the hypothesis that geopolitical boundaries are basically of the same nature as other boundaries between humans in social groups. I show that the organized knowledge humans have about geopolitical boundaries applies to hierarchical boundaries between human groups by reviewing the paradigmatic field of borders: renegociation of border outlines, passports and identity documents, work visas, immigration, tourism, signposts, customs and tariffs, smugglers, stateless persons, border populations. In the second part, I propose the following three qualitative parameters to distinguish between these borders: (i) visibility of categorization criteria, (ii) opportunities for individuals to elude the border paradigm, and (iii) spatial and temporal dimensions and their effects on spaces of intersection. I demonstrate how multiple frontiers interact. In the third part, I show how an analysis in terms of borders captures reality by offering a case study, that of smuggling and smugglers.A French version is available at hal-01249718Read less <