This treatise is not a sermon in the ordinary acceptation of the term. It was not preached, but, according to the Latin usage of the word "sermo," was rather "a discourse," "a discussion," "a disputation" concerning baptism. Even in popular usage, the term "sermon" implies careful preparation and the orderly arrangement of thought. Here, therefore, we have a carefully prepared statement of Luther's opinion of the real significance of baptism. Published in November, 1519, and shortly afterward in a Latin translation,[1] it shows that the leading features of his doctrine on this subject were already fixed. With it should be read the chapter in the Large Catechism (1519), and the treatise Von der Wiedertaufe (1538).[2] The treatment is not polemical, but objective and practical. The Anabaptist controversy was still in the future. No objections against Infant Baptism or problems that it suggested were pressing for attention. Nothing more is attempted than to explain in a very plain and practical way how every one who has been baptised should regard his baptism. It commits to writing in an entirely impersonal way a problem of Luther's own inner life, for the instruction of others similarly perplexed. He is confronted with a rite universally found in Christendom and nowhere else, the one distinctive mark of a Christian, the seal of a divine covenant. What it means is proclaimed by its very external form. But it is more than a mere object-lesson pictorially representing a great truth. With Luther, Word and Spirit, sign and that which is signified, belong together. Wherever the one is present, there also is the efficacy of the other. The sign is not limited to the moment of administration, and that which is signified is not projected far into the distant future of adult years. The emphatic preference here shown for immersion may surprise those not familiar with Luther's writings. He prefers it as a matter of choice between non-essentials. To quote only his treatise of the next year on the Babylonian Captivity: "I wish that those to be baptised were entirety sunken in the water; not that I think it necessary, but that of so perfect and complete a thing, there should be also an equally complete and perfect sign." [3] It was a form that was granted as permissible in current Orders approved by the Roman Church, and was continued in succeeding Orders.[4] Even when immersion was not used, the copious application of the water was a prominent feature of the ceremony. No one is better qualified to speak on this subject than Prof. Rietschel, himself formerly a Wittenberger: "The form of baptism at Wittenberg is manifest from the picture by L. Cranach on the altar of the Wittenberg Pfarrkirche, in which Melanchthon is administering baptism. At Melanchthon's left hand lies the completely naked child over the foot. With his right hand he is pouring water upon the child's head, from which the water is copiously flowing." [5]