Finally, I see on what condition Christianity may remain faithful to itself while realising itself in history. It is only by an incessant struggle of the Christian principle against all the elements of the past which find, alas, in human propensities, and in the inertia of the multitude, a complicity so constant and effectual. So far from religious indifference being permissible, critical action and Christian prayer become, in every church and every life, permanent duties. I now understand the paradox of Christ: "I am not come to send peace on the earth, but a sword." For the Christian principle, in fact, war is life. To cease to fight is to succumb; it is to allow yourself to be submerged by the rising tide of human superstitions; it is to die. Who does not see the danger of allowing Christianity to become absorbed in one church form, Christian truth in one formula, the Christian principle in one of its particular realisations? All these contingent expressions, being imperfect, must be reformed sooner or later. How can they be unless the spirit of Christianity disengages itself without ceasing and floats above them as an ideal? For eighteen centuries a river of life has flowed through human history. Break down the barriers which fanaticism and superstition are always setting up athwart its course. If the waters cease to flow they stagnate, and corrupt and poison the very land it was their mission to fertilise. CHAPTER III THE GREAT HISTORICAL FORMS OF CHRISTIANITY 1. _The Evolution of the Christian Principle_ The distinction between the Christian principle and its successive realisations renders it easy to resolve the question, formerly so much debated, as to the perfectibility of Christianity. It is perfect piety, plenary union with God, consequently the absolute and definitive Religion. But, regarded in its historical evolution, not only is it perfectible, but it must ceaselessly progress, since, for it, to progress is to realise itself. The germ could not be perfected in its essence, as germ and ideal type of the tree that it potentially contains. But the tree itself only comes into existence by the development of the germ. No reform, no progress, no perfecting, could raise Christianity above itself--that is to say, above its principle; for these reforms and this progress only bring it into closer conformity with that principle--that is, make it more Christian. On the other hand, the principle itself must enter into evolution in history in order to manifest its originality and its force, to realise in individual and social life, in the realm of thought and in the realm of action, in a word in the whole of civilisation, all its virtualities and all its consequences. Jesus saw this when He spoke the Parable of the Mustard Seed (Matt. xiii. 31-32).