In his second exposition on Psalm 29 Augustine reflects on the role of Christ as mediator between God and humanity. 

“What does it mean to be a mediator between God and humankind?  Notice that scripture does not say, ‘between the Father and humankind,’ but between God and humankind.  What is God?  Father, and Son, and Holy Spirit.  What are human beings?  Sinners, godless creatures, mortals.  Between the Trinity and the weakness and sinfulness of men and women came the Mediator, made human, not sinful but nonetheless weak, so that he might unite you to God by virtue of his sinlessness, and might draw near to you by being weak.  In this way, then, the ‘Word was made flesh,’ that is, the Word became a human being, so that a Mediator might arise between humanity and God.”

In describing Jesus Christ, the Mediator, Augustine writes that he was “not sinful but nonetheless weak.”  This is an important description.  In order to help mine the richness of what Augustine is proposing we need to go to the famous hymn found in the second chapter of the Letter to the Philippians: 

“Have among yourselves the same attitude that is also yours in Christ Jesus. 

Who, though he was in the form of God,
did not regard equality with God
  something to be grasped.
Rather, he emptied himself,
taking the form of a slave,
coming in human likeness;
and found human in appearance,
  he humbled himself,
becoming obedient to death,
  even death on a cross. 
Because of this, God greatly exalted him
and bestowed on him the name
that is above every name…”  (Philippians 2:5-9)

Both this passage from scripture and Augustine’s assertion raise an important point for reflection – does the salvific event in Christ come through his independent action and strength as Son – the second person of the Trinity – or through the eternally lived communion of Trinity?  I think it is through the latter.  Christ, “emptied himself, taking the form of a slave”.  The Mediator between God and sinful humanity was himself, “not sinful but nonetheless weak”.  These assertions negate any thought of a triumph achieved solely through an exercise of independent action and strength.   

The salvific event in Christ is achieved exactly through the weak humanity of Christ (emptied freely of any claim to the authority of divinity) clinging in obedience to the will of the Father and the grace of the Spirit.  Throughout scripture wherever one person of the Trinity is present there are the other two to be found.  For an example we can look to Matthew’s depiction of the baptism of Jesus:

“After Jesus was baptized, he came up from the water and behold, the heavens were opened for him, and he saw the Spirit of God descending like a dove and coming upon him.  And a voice came from the heavens, saying, ‘This is my beloved Son, with whom I am well pleased.”  (Mt. 3:17)

The proclamations, powers, signs and healings found throughout the ministry of Jesus – from the wedding at Cana all the way to the foot of the cross – are not signs of the Son as second person of the Trinity exercising his “own” power but rather the Son emptying himself of all authority in love and through his weak humanity clinging to the will of the Father and the movement of the Spirit. 

And this is indeed good news for us!  We cannot make a claim on the Mediator in terms of his divinity but we can make a claim in virtue of his weakness!  Augustine points this out for us when he says that the Mediator came, “so that he might unite you to God by virtue of his sinlessness, and might draw near to you by being weak.”  Through the grace of baptism in Christ we now have the claim of brothers and sisters to the Mediator and we have the promise of divinity and kingship not by an exaltation of strength and independent action but by participation in a weakness that clings to God.  In Christ, we also can now cling to the Father’s will and the movement of the Spirit in our lives.  We can do this and we must do this. 

The salvific event is rooted in the grace of weakness and communion.