Near the beginning of his Divine Simplicity (xviii-xix), Paul Hinlickey briefly explains the differences between his “weak” account of simplicity and the “strong” accounts of Thomas and others. In many classic treatments, simplicity is “a rationally evident ontological implication that comes about by analysis of the ground of a stable and manifest cosmos.”
Taking his cues from Deleuze, Hinlickey wants to work out simplicity on the “plan of immanence,” which, theologically, means the plane of the history of Israel and Jesus. Thus, simplicity is “something posited and achieved in a fraught and contested world and thus finally demonstrated in the historical life of a particular claimant to deity by the coming, in Jesus’s language, of the reign of God.” The fact that God “could achieve and demonstrate God’s deity for us in a historical life also bears ontological implications.” The gospel cannot be true unless God is “antecedently powerful enough, wise enough, and good enough to make and keep the promise of the coming of the Beloved Community, thereby demonstrating His deity in a world of His creating.” Thus, there is a “certain immanent or ontological doctrine of divine unity or simplicity, namely, a rule of faith reminding us in all our speech about god we are referring to a singularity – the Creator of all that is not God – the One who is, strictly speaking, incomparable with the quotidian realities familiar to human beings in the world as we know it, who are not sufficiently powerful, wise, or good to give life to themselves, let along to others.”
From this angle, then, divine simplicity isn’t a metaphysical claim or assumption but a “henotheistic or monolatrous rule of faith for believers in a contested world.” It amounts to a statement of the first commandment “to have no other gods before the God of exodus and Easter, the Father of His Son, Jesus Christ, who in the power of their Spirit lays a controversial and controverted claim upon them for exclusive fidelity, one that elicits faith as a disciplined way of life that can be validated only by God’s demonstrated fidelity in turn to His promise at the eschaton of judgment.”
That is a mouthful, and itself a controversial and controverted claim, and whatever one’s final assessment of it, it has some things going for it: It is explicitly Trinitarian; it puts the emphasis on God’s actions in the rough terrain of actual history; it forges an integral link between theology proper and Christian worship of the one God; it has an eschatological trajectory – theology proper is about the God who will be faithful to the end, who will fulfill all He has promised.