Sapientis est ordinare. Ordering is the work of the wise. This interpretation of Bernard Lonergan's systematic theology of God pursues throughout the Pars systematica of his De Deo trino (1964) an idea he does not advert to as constitutive of his method as such, namely the idea of order.The idea of order, I argue, does function methodically in the Pars systematica. As he moves systematically from the nature of God, from God to us, and back to God, Lonergan variously specifies the idea of order in ways integral to both the form and content of his theology, a trinitarian theology of comprehensive scope. These specific instances of order---relating to fundamentals of trinitarian theory, soteriology, subjectivity, intersubjectivity, the natural world, history, and culture---can be related intelligibly to one another. Thus the idea of order informs an emergent viewpoint that facilitates synthetic understanding of Lonergan's complex, sometimes very difficult, systematics of the Trinity. Furthermore, I argue, the explanatory process of interpreting the Pars systematica from the single viewpoint of order can give students means, not too difficult to grasp, whereby they too might gain a synthetic understanding of Lonergan's theology of God sufficient to affirm its comprehensiveness, unity, value, and openness to organic development.The centerpiece of the Augustine-Aquinas-Lonergan tradition of trinitarian theology is the psychological analogy. Drawing from the integral relationship between the intentional operations of the enquiring subject and theological method, I seek to demonstrate that in the Pars systematica and other writings to 1964, especially Insight, Lonergan provides a way to express from the viewpoint of order the intelligible unity among God quoad se (the immanent Trinity), God quoad nos (the economic Trinity), and the "everything else" comprised by the category Creation. My argument also emphasizes the relevance of Lonergan's theology of God to Christian living, especially to the subjectivity and work of the theologian.My interpretation also aims to provide the student of Lonergan's thought with data sufficient to answer adequately the question of meaning posed by this text from the Pars systematica: Although all other goods of order imitate ad extra [external to God] that supreme good of order to be perceived in the Holy Trinity itself, it is nonetheless fitting that the economy of salvation, which is ordered to participation in the very beatitude of divinity, not only imitate the order of the Holy Trinity but also in some manner participate in that same order.