Why the existence of Christ Jesus cannot be proved historically

"In fact, the existence of Christ Jesus cannot be proved historically, as Caesar's or Napoleon's can be. And why? Because the Mystery of Golgotha was intended to confront us with an event to which we should have supersensible access only. In order that human beings might learn, precisely by means of the Mystery of Golgotha, to raise themselves to a supersensible perspective, there could be no external, physically documented proof of the event."   — Rudolf Steiner, September 23, 1919