On the Trinity

Augustine spent two decades on this work, and the effort shows. On the Trinity is the most sustained exploration of the triune God in Western theology. The first seven books expound the scriptural and doctrinal foundations; the later books turn inward, searching for analogies of the Trinity in the human mind itself — in memory, understanding, and will. Augustine is the first Christian thinker to systematically explore the mind as an image of the Trinity, and his conclusions shaped every subsequent Western treatment of the doctrine. The work is difficult, honest about its own difficulties, and occasionally luminous. Augustine himself was unsatisfied with it — it was published against his wishes after a draft was circulated prematurely — but its influence has been incalculable.

On the Trinity is a central text in the Christian mystical tradition, offering insight into the spiritual life, the nature of divine union, and the transformation of the soul.