This article contributes to a recent shift in the study of early modern political thought, moving away from a state-centric view of the period towards an interest in the political significance of a range of other communities. More specifically, I argue that debates about the scope of one key concept, that of societas, resulted in different visions of the relationships between a variety of human associations. To demonstrate this, I reconstruct Johannes Althusius’s theory of societas and compare it to those of several contemporaries, ranging from Renaissance Ciceronianism to Jean Bodin and Hugo Grotius. I show that Althusius provided an innovative juridical interpretation of societas, which he used to ground a conception of politics according to which all human associations, from the family to the corporation to the state, are political. This complements traditional theological interpretations of his thought, which alone cannot fully account for its distinctiveness. Althusius’s conception of politics enabled him to chart an original middle way between two options available at the time: on the one hand, the isolation of politics from social and religious life; on the other, its subordination to or full identification with other kinds of community.