“Oportet igitur ut Creatorem, per ea quae facta sunt, intellectum conspicientes (Rom. 1:20), Trinitatem intelligamus, cuius in creatura, quomodo dignum est, apparet vestigium. In illa enim Trinitate summa origo est rerum omnium, et perfectissima pulchritudo, et beatissima delectatio.”
“Thus it is necessary, as we behold the Creator intellectually through those things which were made (Rom. 1:20), that we should understand him as Trinity, of whom in creatures, as it fitting, there appears a trace. For in this Trinity is the highest origin of all things, and the most perfect beauty, and the most blessed delight.”
—De Trin. VI.10.12
This is a programmatic statement for the second half of De Trinitate: because we can find traces of God in creation, we should expect those traces to be Trinitarian in form.