A theology of creation requires clarity about trinitarian doctrine, especially the relation of the one divine essence to the three persons, the distinction between immanent and transitive acts, and the indivisibility of God's outer works. The triune God is one undivided essence in an irreducible threefold personal modification. The persons of the godhead are distinguished from each other by mutual relations and by each person's proper characteristics; these relations constitute God's immanent perfection anterior to creation. The work of creation is a non-necessary, novel and voluntary work of the Trinity. As an outer work it demonstrates God's unity: the work of creation is not divisible into three distinct actions. But distinct and eminent appropriation of specific acts to specific persons is permissible if each person is understood as a mode of the one divine essence. Creation is thus a common work of the undivided three-in-one; there are not three creators, but three who create.