Here is an odd question for you: what would count as evidence that you were in the presence of God incarnate? What facts or occurrences would qualify as good rational grounds to conclude that this human being was also, in reality, God the Lord, creator of all things visible and invisible?
What things spring to mind?
Virgin birth - assuming that could be verified beyond a doubt, which I suppose it could nowadays? Miracles - assuming that they were well-attested and we were sure there was no trickery involved? Inspired teaching - assuming that it really did go beyond anything that anyone else had said? Resurrection from the dead - assuming that this, too, could be verified absolutely, including a careful check that real death had occurred?
Or perhaps a cumulative case built up out of all the above?
Now, I have no interest in shaking anyone's faith. But I do want to point out that, as far as I can tell, it would not be legitimate to draw the conclusion that I was in the presence of God incarnate from any of those things, or indeed all of them put together. They are all remarkable, but frankly remarkable things do happen in the world. Taken together, they certainly seem to point to the action of some higher power, but we know that there are many powers at work in the universe.
We are faced here with an epistemological problem. What criteria could one apply to ascertain whether something absolutely unique had occurred? And here we do mean 'absolutely unique'. If God enters into his creation as a man, that is an event without parallel or analogue. It is not just one of those remarkable things that happens from time to time, and that is why none of the remarkable things mentioned can be sufficient evidence of it. Our categories of knowledge break down when we cannot compare an event with something similar, or at least something with which it stands in basic continuity. But there is no immediate continuity between the incarnation of God and any other event in all creation, because there is no immediate continuity between God and his creation. They are not in the same class of being.
Of course, it is necessary to our faith that all these things have actually happened and been true. They are necessary, but not sufficient, reasons to trust that Jesus Christ is my Lord and Saviour, as he is to the whole world. But I think there is something significant in the fact that the most dazzlingly revelatory events - the Transfiguration, say, or indeed the resurrection itself - have deliberately very limited audiences. And even those audiences contain doubters and deniers - think of the guards at the tomb, or the 'but some doubted' of Matthew 28.
So, what are we to say to this?
Firstly, I think there is something we can say about continuity. The incarnation does stand in continuity with the history of Israel, or to be more precise (but less temporally straightforward) the history of Israel stands in continuity with the incarnation. In the light of Israel's history, we can understand Jesus as the mighty God come to save his people.
But secondly, we must recognise that even this connection can only be seen if we are given eyes. We can rehearse the evidences, the signposts that something extraordinary is happening in the life, death, and resurrection of Christ. We can highlight the sense that he makes of Israel's history, and vice versa. But ultimately, unless it is shown us - shown to each of us personally - we cannot see it.
Veni Creator Spiritus!