SummaryGrotius has a rudimentary theory of sociability. Only with hindsight has a remark about appetitus societatis been promoted to the starting point of a theory that flourished in the writings of later natural jurists. In this article, I address the issue of the appearance in Grotius's natural law of sociability [as the 1715/38 English translation of John Morrice renders appetitus societatis, following Barbeyrac's sociabilité]. Writing in the just war tradition, Grotius is first of all interested in finding out the conditions (...) for peace, and although injustice is a condition of war, it is not per se true that injustice is a perversion of society. Apparently, not all societies are perfect and the violence of war and the legal actions of peace are both instruments for achieving a greater modicum of justice in this world. Yet appetitus et custodia societatis is called the foundation of justice. Grotius achieved this context for sociability in phases, through a series of writings from c. 1600 until De iure belli ac pacis of 1625, and its revision of 1631. In this development the notion of fides plays an intriguing role, through which we can obtain a better understanding of the meaning of appetitus societatis in the later work. The present article is a sequel to a previous publication, on fides in De iure praedae. Analysing the genesis of appetitus societatis in De iure belli ac pacis, I argue that Grotius was changing his strategy over the years, without however arriving at a definitive solution to the question of what commits men to the pursuit of justice. (shrink)