Book excerpt: The Holy Spirit and Moral Action in Thomas Aquinas is a detailed study of how, according to one of Christianity’s greatest visionary thinkers, God’s Holy Spirit is continuously at work in and through humanity’s moral activity. Jack Mahoney, SJ, documents, notably from Aquinas’s commentaries on scripture, how “the grace of the Holy Spirit” prompts and influences people’s minds, as well as their decisions to act, occasionally in unexpected ways. Through the gift of connatural wisdom, the Spirit empowers humans to appreciate God’s own wise and loving design for the whole of creation, and enables them to cooperate freely in fulfilling their unique part in it.