The problem, happily, is simplified for the historian and the psychologist. In asking what is the principle of Christianity, what do we wish to know? Simply what it is that makes a Christian a Christian. We desire to ascertain what is the inward element, present in the soul, which compensates, at need, for the absence or defect of all the rest, and which, being wanting, cannot be supplied or compensated for by anything else. In short, we want to get at the religious experience which determines and marks out the consciousness of all Christians, which makes them members of one moral family, and which makes them to be recognised as such in spite of differences of times and place, of language and of culture, of rites and even of beliefs. To seize this common feature there is no need of polemics; all we need is a little history and psychology. In history, Christianity offers itself to us as the term and crown of the religious evolution of humanity. In the consciousness of the Christian it is something more; it there reveals itself as the perfect religion. How must we understand this perfection? Is it the perfection of a complete system of supernatural knowledge, of a religious science which would have been strange to former generations, and which was shared by Christians alone? In no wise. If there are enlightened Christians, there are many who are very ignorant. And yet they are all Christians by one and the same principle, which is entirely independent of degrees of culture. No Christian will maintain that his knowledge is perfect. They all agree with St. Paul that at present it is very imperfect. We see divine things dimly. What, then, do they affirm who say with so much assurance that Christianity is the perfect religion? They affirm that, religion not being an idea but a relation to God, the perfect religion is the perfect realisation of their relation to God and of God's relation to them. And this is not, on their part, a theoretical speculation; it is the immediate and practical result of their inward experience. They feel that their religious need is entirely satisfied, that God has entered with them, and they with Him, into a relation so intimate and so happy that, in the matter of practical religion, not only can they imagine nothing, but that they can desire nothing above it or beyond. They simply set themselves to realise more fully and more effectually in themselves this supreme relation, this piety whose principle is immanent to themselves; they know that in it they have the germ of perfect spiritual development and eternal life. This is why they affirm without the slightest doubt that Christianity is the ideal and perfect religion, the definitive religion of humanity. Such is the first affirmation of the Christian consciousness. Here is the second.