In the last post I offered the first two of five arguments against the "two-natures" interpretation of Romans 1:4. The first was my observation that for many commentators any other interpretation of Romans 1:4 might open the door to Adoptionist or Arian theological sympathizers. The second argument was that translating 'orizo as "declare" or "manifest," although possible, does not get at the root meaning of the word. Translating this as "appoint" should not be abandoned by orthodox commentators and theologians simply because it threatens to be theologically suspect or troublesome.
Third, I will discuss in later posts the rich web of associations and images connected with the concept of sonship in the Old and New Testaments, but for now it ought to be enough to recognize that the meaning of the designation “Son” even when applied to Jesus cannot be determined before the immediate context is consulted. Even in the space of two verses Paul uses "son" in two different, but not unrelated ways. "Son" occurs twice in verses 3-4: once at the head of the peri clause in verse 3, and then again in verse 4. The gospel is “from” and “about God” but it is further marked off as the "gospel of/concerning his son" (v. 3).
As Douglas Moo observes, this assertion in verse 3—that God’s son “has come” or “was born”—assumes the pre-existence of the Son. There are other passages from Romans (8:2, 32) and in the New Testament that also refer to the mystery of Jesus’ pre-incarnate life as the Son of the Father (Heb. 1:2; 1 Cor. 8:6; Gal. 4:4; Phil. 2:6ff.; Col. 1:13, 16-17; John 3:17; 1 John 4:10). It was fitting for him to become the incarnate Son because he was (or is) the eternal Son/Image of the Father (see Philip Edgcumbe Hughes, The True Image: The Origin and Destiny of Man in Christ [Grand Rapids, MI: Wm. B. Eerdmans, 1989], pp. 213-223). John chapter 1 describes the coming of the Word into the world as the manifestation of the glory of eternal Son of the Father (John 1:14), the “only begotten” or “unique” God who is in the bosom of the Father. John evidently understands Jesus’ Sonship to imply a state of existence that refers beyond temporality (John 8:58; 12:41).
Fourthly, in Romans 1:2-4, there is evidence of an historical or linear movement: the eternal Son becomes a descendent of David according to the flesh and then subsequently, upon his resurrection, is appointed as the Son of God with power. Apparently, then, he was ontologically the Son of God even before he became man in the economy of salvation. The “sending” spoken of in John 3:17 and Gal. 4:4 and implied in Rom. 1:3 cannot merely refer to a “prophetic sending” as some have argued, but presuppose pre-existence as the starting point of Jesus’ mission. So let's just clear the air right now: I'm not denying the eternal sonship of Jesus.
If, as I will argue, “Son of God” has a “theocratic” meaning in verse 4, then Paul adds something to his earlier use of "son." Just as the assertion that the Son “became of the seed of David” implies that the Son came into a new mode of existence, so to speak, kata sarx, so also with the resurrection, the eternal Son as man has been appointed the “Son of God with power” according to the Spirit of holiness. This comparison between the Son’s existence kata sarx and kata pnuema does not contrast his outward or external physical life with his internal, Spirit-perfected vitality, which then qualifies him to be the Son of God in power. Nor, as we have seen, does the contrast distinguish between the human and divine natures of Jesus.
Rather, the contrast between sarx and pneuma “is part of Paul’s larger salvation-historical framework, in which two “aeon’s” or eras are set over against one another: the old era dominated by sin, death, and the flesh, and the new era, characterized by righteousness, life, and the eschatological gift of the Holy Spirit” (Douglas Moo, The Epistle to the Romans [Grand Rapids, MI: Wm. B. Eerdmans, 1996], p. 50). This essay is not the place for an extended discussion of Paul’s eschatological use of the sarx-pneuma contrast. Nevertheless, as a redemptive-historical contrast it supports the interpretation that we have been arguing for here—that Jesus was appointed by the Father as the Son of God with power upon his resurrection from the dead.
Fifth, Paul says that the incarnate Son has been “appointed Son-of-God-with-power” or possibly “Son-of-God-in-power.” I understand "in power" to modify "son of God" (RSV) and not the verb "to appoint" (NASB; NIV). What we have here, then, is a clear distinction between the eternal Son’s assumption of human nature ("who was descended from David according to the flesh", v. 3), indeed his entrance into the “old age” of dominated by sin and death, and his post-resurrection appointment as “Son of God with power” Douglas Moo explains:
What Paul is claiming, then, is that the preexistent Son, who entered into human experience as the promised Messiah, was appointed on the basis of (or, perhaps, at the time of) the resurrection to a new and more powerful position in relation to the world. By virtue of his obedience to the will of the Father (cf. Phi. 2:6-11) and because of the eschatological revelation of God’s saving power in the gospel (1:1, 16), the Son attains a new, exalted status as “Lord” (cf. V. 4b). Son of God from eternity, he becomes Son of God “in power” . . . . the transition from v. 3 to v. 4, then, is not a transition from a human messiah to a divine Son of God (adoptionism) but from the Son as Messiah to the Son as both Messiah and powerful, reigning Lord (Moo, The Epistle to the Romans, pp. 48-49).