Proceeding from the notion of borders as productive of difference and identity, this chapter explores two alternative ontologies of thinking the productiveness of borders. The focus is, on the one hand, on the tradition of thought based on certain Hegelian reflections taking place in Jacques Derrida’s work, and on the other on the Spinozian tradition reflected in the work of Gilles Deleuze. In the discussion the chapter takes as its point of reference two very different concrete historical cases of the activity of drawing borders, one being a drawing of a political border on the map of Europe in 1809 between Sweden and Russia, and the other being an epistemic border drawn in the discourses on sexualities in the late nineteenth century; both had multiple subsequent effects of terms of identities and differences.