The article derives from Theodore of Mopsuestia’s Commentary on the Gospel of John, wherein Theodore describes how he understood Christ’s two natures being united in “one common proso¯ pon.” He regards proso¯ pon not as a synonym for hypostasis, as the Second Council of Constantinople did, but as the functional union of Christ’s two natures acting as one “ego.” Theodore finds this understanding in the diverse ways John portrays Christ acting at times as one reality and at other times in clearly divine and human ways, with each presumed in the other.