Recently, the idea of a world order which would guarantee universal peace, obeying the rule of law not the rule of force, has frequently been evoked, though not without second thoughts. This ideas originates in the eighteenth century, and particularly in Kant. Hence it is first of all to understand where our own ideas come from that we should reread the pages he devotes to this theme. At the same time, rediscovering the sense and the function of cosmopolitan law in Kant avoids letting it simply be confiscated by those who adopt it.