 In the eighteenth century, Charles Castel, Abbé de Saint-Pierre (1658–1743), in his Project for Making Peace Perpetual in Europe (1713), extended Hobbes’s argument that a rational interest in self-preservation necessitated the creation a domestic leviathan to the international realm, asserting that reason should lead the princes of Europe to form a federation of states by social contract. The contracting sovereigns would form a perpetual and irrevocable alliance, establishing a permanent Diet or Congress that would adjudicate all conflicts between the contracting parties. The federation would also proscribe as “a public enemy” (Rousseau 1756 [1917: 63]) any member who breaks the Treaty or disregards the decisions of the congress; in such a situation, all members would “arm and take the offensive, conjointly and at the common expense, against any State put to the ban of Europe” in order to enforce the decisions of the federation (1756 [1917: 61–4]). In other words, perpetual peace can be achieved if the princes of Europe would agree to relinquish their sovereign rights to make war or peace to a superior, federal body that guaranteed protection of their basic interests.