In his epistle to Serapion, Athanasius gives his most extensive consideration to pneumatology. As in his debates with Arians, Athanasius consistently focuses attention back to the pattern of biblical language, what Anatolios calls the “intertextual scriptural characterizations of Father, Son and Spirit.”

For instance: We are made “sons” when we receive the Spirit, and therefore the Spirit is the “one who actualizes our adoption into Christ.” The Father is light, and the Son is the radiance of His glory; the Spirit “is the one in whom we are enlightened.” The Father is fountain, the Son is the outpouring, and we drink the Spirit. The Father is wise, the Son His Wisdom, the Spirit makes us wise.

As Anatolios notes, “the Spirit [is] the one in whom the outward manifestation and activity of the Father and Son is actualized in relation to us. In each case, the Spirit is thus characterized as the point of contact between God and creation.” The Father is “source,” the Son “outgoing manifestation and imaged content of the source,” and the Spirit “the outward actualization of that content in and toward creation.” One of the key points is that “the actualization is precisely actualization of the content that is in Christ” and nothing else. In creation and in redemption the Spirit has “nothing else” to do than to actualize the Word who is the manifestation and speech of the Father.