Such is the feeling with which we should approach the history of Christianity. The field is vast; the vegetation in it is infinite; we must content ourselves with incompleteness. Being neither able nor desirous to say everything, I have been obliged to seek a commanding point of view from which it would be possible to take in that history in its entirety, and to take a bird's-eye view of the course it has followed. Faithful to this idea, namely, that the Christian principle is like leaven or a seed thrown into a gross, heavy mass of anterior traditions which it was meant gradually to raise and to transform, it is this struggle and this progress that I desire especially to describe. I shall endeavour to show how Christianity, always borrowing its forms from the environment in which it realises itself, after enduring them for a time, subsequently frees itself from and triumphs over the inferior and temporary elements which fetter it, and manifests from age to age a greater independence and a purer and higher spirituality. This progress is slow, obscure, oft interrupted, hindered by reactions or by moments of arrest; none the less striking, however, does it appear when, rising above these secondary complications, one measures the distance between the points of departure and arrival. Not only has Christianity never been better understood than in our own day, but never were civilisation or the soul of humanity taken in their entirety more fundamentally Christian. When one follows the history of Christianity from this higher point of view, one sees that it has passed through three very distinct phases and assumed three essentially different forms: the Jewish or Messianic, the Graeco-Roman or Catholic, the Protestant or modern, form. Let us see how it has passed from the one to the other. 2. _Jewish, or Messianic Christianity_ The first of these periods is usually omitted or suppressed. Being unable to admit that Catholicism is not the work of Christ and the apostles, or that the Church has varied its dogma or its institutions, Catholic theologians naively imagine that the first Christian communities of Jerusalem and Antioch resembled those of Rome, Milan, and Lyons in the fourth century; that Peter was the first of the popes and exercised for five-and-twenty years the supreme pontificate; that the apostles appointed bishops everywhere as their successors and the heirs of their power. In this way the history of Christianity became, in the Catholic tradition, a tissue of legends.