This chapter illustrates the way in which –particularly over the last three hundred years or so –the fault lines do not simply run between philosophy and theology but often across them. A theology of God's aseity is an indication of the one who is and acts thus, who is the object of the church's knowledge, love and fear, and whose praise is the church's chief employment. In Christian dogmatics, such a materially rich notion of aseity cannot be articulated apart from the doctrine of the Trinity, for it is that piece of teaching which offers a conceptual paraphrase of the life of God, both in his inner depth and in his gracious turn to that which is not God. Both the pathology and the material exposition sketched here suggest that an account of aseity goes wrong when it is alienated from its proper Trinitarian setting and deployed to perform different functions.