Beginning in chapter one of his book Incarnation: The Person and Life of Christ (pages 1-2) it reads:
Our task in christology is to yield the obedience of our mind to what is given, which is God’s self revelation in its objective reality, Jesus Christ. A primary and basic fact which we discover here is this: that the object of our knowledge gives itself to us to be apprehended. It does that within our mundane exisitence, within our worldly history and all its contingency, but it does that also beyond the limits of previous expereince and ordinary thought, beyond the range of what is regarded by human standards as empirically possible. Thus, when we encounter God in Jesus Christ, the truth comes to us in its own authority and self sufficiency. It comes into our experience and into the midst of our knowlege as a novum, a new reality which we cannot incorporate into the series of other objects, or simply assimilate to what we already know….
And yet Jesus Christ gives himself to be known as the object of our experience and knowledge, within our history and within our human existence – but when we know him there, we know him in terms of himself. We know him out of pure grace as one who gives himself to us and freely discloses himself to us. We cannot earn knowledge of Christ, we cannot achieve it, or build up to it. We have no capacity or power in ourselves giving us the ability to have mastery over this fact. In the very act of our knowing Christ he is the master, we are the mastered. He manifests himself and gives himself to us by his own power and agency, by his Holy Spirit, and in the very act of knowing him we ascribe all the possiblity of our knowing him to Christ alone, and none of it to ourselves.
But let us note: it is only when we actually know Christ, know him as our personal saviour and Lord, that we know that we have not chosen him but that he has chosen us; that it is not in virtue of our own capacity to give ourselves the power to know him; that it is not in virtue of our own power or our own capacity that he gives us to know him, but in virtue of his power to reveal himself to us and to enable us to know him; that is, faith itself is the gift of God. Or let me put that in another way; when we know God in Christ, we do not congratulate ourselves on our own powers of intuition or discovery, and pat ourselves on the back because we have been able to see that there is more in Jesus than meets the eye, that God is there himself. No, we do the exact opposite: we acknowledge that in knowing God in Christ, we do so not by our own power, but by the power of God.