If two or more substances, distinct in essence not merely in number, can form a union, it is little wonder that collections of such composites can also form unions. The difference between the union of mind and body and social and political unions, however, is that the latter depend not upon God (directly) but upon the wills of individual humans who create them. The force behind the creation of communities is a passion, love, which Descartes defines as a willing to join oneself in union with others. As a passion, love is dependent upon the body, and as an act of will, upon the divine element within the soul. It is argued in this chapter that such unions rely on organizational and mereological principles similar to those which account for the integrity of organic bodies. It is from here that the idea of a “body politic” emerges, demonstrating the continuity of Descartes’ thinking in natural philosophy, politics, and ethics.