The objection
If only the Son can become human, he possesses an ability the Father lacks. If, by contrast, the Father could also become human, the Son's mission seems arbitrary.
1. Not having happened does not mean inability
Scripture reports that the Son became human. It does not follow without further justification that the Father or Spirit lacks divine power. A historical and personal determination must not automatically be translated into a hierarchy of abilities.
Nor does shared power entail that all persons occupy the same personal position. The Father is not the Son. This distinction is no defect needing to be remedied by additional omnipotence.
2. Thomas distinguishes possibility and fittingness
Thomas answers affirmatively whether another person's incarnation is possible because divine power is shared. In such a thought experiment, human birth would make the Father the son of a human mother, but not the Father's eternal Son.[1]
This is a metaphysical judgment within his model, not an explicitly revealed account of another salvation history. It does show, however: Classical theology need posit no particular creative power of the Son lacking in the Father to confess his actual incarnation.
3. A free action can nevertheless be deeply grounded
The alternative “necessary or arbitrary” is false. An action can be free and simultaneously perfectly fitting to its intention. John connects the Logos through whom everything was created with the Logos who becomes flesh. Colossians 1 connects creation and reconciliation in Christ.
Galatians 4 leads from the sending of the Son to the redeemed's sonship and the Son's Spirit. These connections are no accidental embellishment. The eternal Son brings people into fellowship with his Father. Thomas develops precisely such reasons of fittingness without deriving an additional divine ability from them.[1]
4. Certainty concerns God's actual action first
We need not be able to describe every conceivable alternative world completely to know who became human for us. Revelation directs our gaze to the Son whom the Father actually sent.
The objection therefore misses its target in both directions. It proves neither inferior power of the Father nor meaninglessness of sonship. It confuses shared divine perfection with salvation's personal form. Shared power permits different personal relationships; the revealed mission determines which relationship manifests itself in incarnation.
5. What makes the Father precisely the Father?
The persons are distinguished neither by different bodies, different degrees of deity nor arbitrary names. The classical explanation names their relationships of origin: The Father is Father of the Son; the Son is from the Father; the Spirit proceeds. These relationships are no interchangeable labels on three previously similar divine individuals.[2]
A different possible task toward the world must therefore not be confused with exchanging eternal identity. Even if one considers the Father's incarnation possible with Thomas, the Father would not thereby become the Father's eternal Son. Assumed human nature designates what a person additionally assumes; their eternal relationship designates who this person is. The question of possible missions thus does not replace the question of personal identity.
Biblical texts in context
Sources and further study
- Thomas Aquinas, Summa theologiaeIII, q. 3, a. 5 and a. 8: possibility of assuming human nature and particular fittingness of the Son's incarnation.
- Thomas Aquinas, Summa theologiaeI, q. 40, a. 2: the personal relationships of origin distinguish the persons.