The frontier, increasingly decried in Western countries over the past sixty decades, is now making a comeback. Talk of a world without borders is no longer so appealing, for a number of reasons. Russia's invasion of Ukraine is a powerful demonstration of the absurdity of talking about independence without territory. What's more, it's clear that the idea of a united Europe in the face of the many challenges of our times (war, terrorism, immigration...) requires recognition of its external borders, which are extensions of the internal borders of the countries that make it up. Borders are the markers of a country's history: they define its contours, not only geographically, but also culturally. At least, that's the idea behind Régis Debray's Eloge des frontières.