This book is a detailed study of how, according to Thomas Aquinas, God’s Holy Spirit is continuously at work in and through humanity’s moral activity. Jack Mahoney, SJ, documents from Aquinas’s interpretation of scripture his portrait of the Holy Spirit in action, showing that for Aquinas, the grace of the Holy Spirit was a matter of the prompting or instigation (instinctus) of the Holy Spirit, who drives God’s children in their decisions (Romans 8:14) and enlightens their minds through the law of the Spirit of life (Romans 8:2).

Mahoney examines Aquinas’s descriptions of various biblical characters responded in the Spirit to personal moral choices and dilemmas, sometimes in unexpected ways, and how the same can happen today, especially in the light of biblical and Aristotelian teaching on the flexible application of general moral rules in varying circumstances. He elaborates the three constants that serve for Aquinas as criteria for authenticating the Spirit’s dynamic presence in people’s moral activity. Finally, Mahoney shows that the overarching structure of Aquinas’s thought on the Holy Spirit’s role is the deployment in history of God’s all-embracing wisdom, ordering all things well (Wisdom 8:1).