When developments in Christianity are spoken of, it is sometimes supposed that they are deductions and diversions made at random, according to accident or the caprice of individuals; whereas it is because they have been conducted all along on definite and continuous principles that the type of the Religion has remained from first to last unalterable. What then are the principles under which the developments have been made? I will enumerate some obvious ones. 2. They must be many and positive, as well as obvious, if they are to be effective; thus the Society of Friends seems in the course of years to have changed its type in consequence of its scarcity of principles, a fanatical spiritualism and an intense secularity, types simply contrary to each other, being alike consistent with its main principle, "Forms of worship are Antichristian." Christianity, on the other hand, has principles so distinctive, numerous, various, and operative, as to be unlike any other religious, ethical, or political system that the world has ever seen, unlike, not only in character, but in persistence in that character. I cannot attempt here to enumerate more than a few by way of illustration. 3. For the convenience of arrangement, I will consider the Incarnation the central truth of the gospel, and the source whence we are to draw out its principles. This great doctrine is unequivocally announced in numberless passages of the New Testament, especially by St. John and St. Paul; as is familiar to us all: "The Word was made flesh and dwelt among us, full of grace and truth." "That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life, that declare we to you." "For ye know the grace of our Lord Jesus Christ, that, though He was rich, yet for your sakes He became poor, that ye through His poverty might be rich." "Not I, but Christ liveth in me, and the life which I now live in the flesh, I live by the faith of the Son of God, who loved me and gave Himself for me." 4. In such passages as these we have 1. The principle of _dogma_, that is, supernatural truths irrevocably committed to human language, imperfect because it is human, but definitive and necessary because given from above. 2. The principle of _faith_, which is the correlative of dogma, being the absolute acceptance of the divine Word with an internal assent, in opposition to the informations, if such, of sight and reason. 3. Faith, being an act of the intellect, opens a way for inquiry, comparison and inference, that is, for science in religion, in subservience to itself; this is the principle of _theology_. 4. The doctrine of the Incarnation is the announcement of a divine gift conveyed in a material and visible medium, it being thus that heaven and earth are in the Incarnation united. That is, it establishes in the very idea of Christianity the _sacramental_ principle as its characteristic.