After a hiatus of several years, in which high teaching loads permitted him to write only little, Kant turned to what would be the culmination of his systematic cosmology. As the New Elucidation had already shown, the analysis of the interactive natural community points to an absolute and transcendent ground. The contemplation of nature inexorably leads to a reflection over the absolute. Kant examined the perfection of dynamic interactivity and its sustaining divine unit in the Essay on Optimism (1759), arguing that relative natural perfection amounts to the harmony of a manifold with a rule, and that absolute divine perfection is such that its manifold contains within itself the ground of reality (2:30–31note). Their difference, in terms of reality or perfection, is just a matter of degree (2:31.16)—the thrust and limit of the cosmic vector. In 1762, now pushing forty, Kant resumed this line of inquiry and wrote what would be his third book, Only Possible Ground of a Demonstration of God’s Existence (1763). Kant explores there the divine limit of the natural vector. “God” is defined as the necessary, unified, and constant being.