The Perfectly Simple God challenges the reading of Aquinas that finds independent treatises of the one God and the Trinity. D. Stephen Long posits that the two are not independent but rather are inextricably related and entail one another. In this, Long provides a constructive rereading of Aquinas, the patristic tradition and the Reformers. Longs constructive interpretation of Aquinas also takes into account challenges to the classical tradition posed by modern and contemporary theology and philosophy to offer a fresh, robust articulation of divine Trinitarian agency for a contemporary age.