The mystery of Christ is presented to us within history --- that historical involvement is not an accidental characteristic of the mystery but essential to it. That is the problem.
Let us first put it this way, recalling the bi-polarity of our theological knowledge. If God has become man in the historical Jesus, that is an historical event that comes under our historical examination so far as the humanity of Jesus is concerned, but the fact that God became man is an event that cannot be appreciated by ordinary historical science, for here we are concerned with more than simply an historical event, namely, with the act of the eternal God. So far as this event is a fact of nature it can be observed, and so far as it is historical in the sense that other natural events are historical, it can be appreciated as such; but the essential becoming behind it cannot be directly perceived except by an act of perception appropriate to the eternal event. That act of perception appropriate to an eternal act, or divine act, would surely be the pure vision of God, which we do not have in history. Here on earth and in time we do not see directly, face to face, but see only in part, as through a glass enigmatically, in a mystery. We see the eternal or divine act within history, within our fallen world where historical observation is essential. Faith would be better described then as the kind of perception appropriate to perceiving a divine act in history, an eternal act in time. So that faith is appropriate both to the true perception of historical facts, and also to the true perception of God's action in history. Nor is it the way we are given within history to perceive God's acts in history, and that means that faith is the obedience of our minds to the mystery of Christ, who is God and man in the historical Jesus. What is clearly of paramount importance here is the holding together of the historical and the theological in our relation to Christ.
If the two are not held together, we have broken up the given unity in Christ into the historical on the one hand, and the theological on the other, refracting it into elements which we can no longer put together again. We then find that we cannot start from the historical and move to the theological, or from the theological and move to the historical without distortion, and nor can we rediscover the original unity. We can only start from the given, where the historical and the theological are in indissoluble union in Christ. [Thomas F. Torrance, Incarnation, 6-7]
This means that we cannot start with an abstracted history (like a naked evidentialism) and seek to attach this to the history of Jesus, but the history we have, in itself, of Christ's revelation is the given reality itself; there is nothing else that can be determinate of that, other than the truly and self-determinately free God himself.
*A repost for those who may have not read this, I once posted this not too long ago at my EC (Wordpress) blog.