Spiritus sanctus; Jn 6:27; Heb 1:8). Why is the sum of three “is-es” still one? During the patristic period, the Latin/Western and Greek/Eastern churches used substantia/ousia (“essence/nature”) to speak of the oneness of God, and persona/prosōpon/hypostasis (“person”) to speak of the threeness of God. In our modern English usage, person means an individualized being with their own personality (thus Karl Barth refused to speak of God as three persons).11 In antiquity, however (e.g., Tertullian),
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