The Very Heart of Faith in Christ

But he said to me, “My grace is sufficient for you, for my power is made perfect in weakness.” Therefore I will boast all the more gladly of my weaknesses, so that the power of Christ may rest upon me.  For the sake of Christ, then, I am content with weaknesses, insults, hardships, persecutions, and calamities. For when I am weak, then I am strong.
2 Corinthians 12:9–10

It should now be clear that when Paul speaks in this way he is not merely making a virtue out of the necessity of his bodily and spiritual sufferings, nor is he simply attempting an ad hoc defence against the attacks aimed at his person.  What he says is to be understood in terms of the very heart of his faith in Christ, which is faith in the Crucified; and it is on this basis that his words define the fundamental meaning of his existence as Christian and apostle.  Life in Christ is life in hope, and can be comprehended only as the very antithesis of all earthly satisfaction, just as the Cross is the sign of divine life only in antithesis of all the glamour and glory of the world.  Christ's glory and the glory of this age, the wisdom of God and the wisdom of men, boasting of one's natural powers and boasting of one's weakness, are things that can never co-exist nor be made, so to speak, compatible with one another.  Paul consciously holds fast to this truth not only as a man but also in his role as an apostle; it characterises his mode of operation. 'If I were still pleasing men, I should not be a servant of Christ' (Galatians 1:10).  Paul carries out his work 'in weakness and in much fear and trembling' (1 Corinthians 2:3, 1 Thessalonians 2:2), and explicitly refuses to commend his testimony by means of the glamour of bewitching rhetoric or of supposedly higher wisdom (1 Corinthians 2:1, 4, 13).  It is by suffering for his congregations that he brings about their salvation (2 Corinthians 1:6).  Only so can he remain truly the apostle of his Lord, the crucified Christ, who is to the Jews a scandal and to the Greeks foolishness, but who in this human nothingness at the same time reveals to both of them the power of God and the wisdom of God (1 Corinthians 1:22-24).

--Hans von Campenhausen, Ecclesiastical Authority and Spiritual Power, p. 41