In the Vesica Piscis (_vide_ frontispiece) we see two Equilateral Triangles formed on the same base, similar to what we found in the ground-plan of Chartres and other Gothic Cathedrals; these two triangles symbolised to the Mediaeval Builders the Divine and Human Natures of the Logos, the Word, the Creator; they are both procreated and enclosed in the Vesica; the one having the Apex pointed upwards, represented Divine or Spiritual Life, and in that I have placed the "Tetragrammaton," the Word or name of God (Jehovah), which, throughout the Jewish race for thousands of years, was held to be so sacred that they did not dare to utter it aloud. It was, at this time, depicted in the Equilateral Triangle, the symbol of the Logos, becoming thus the Masonic Word of the Middle Ages, and was probably used, exoterically, for purposes of recognition among members of the Great Building Societies, with the introduction of Gothic Architecture; but the _esoteric_ teaching, which was known only to the elite of the Craft and not by the Ordinary Operatives, was the mystical _procreation_ of that triangle, the doctrine of Spiritual or New Birth, symbolised by that mysterious figure which we have seen was the very foundation stone of Geometry, and therefore of Tectonic Art, the Head of all learning, and the great Secret of Gothic Architecture, called for esoteric purposes "Vesica Piscis." The Triangle, having the Apex pointing downwards, represented Human or Physical Life, and I have placed therein a representation of _sacrificial_ death, which we shall see was introduced, as a necessity, for the good of the Race. As "everything in Heaven has its counterpart on Earth," so may we see, by introspection, that the _reflecting_ surface, the thin, physical film between the Human and Divine, is represented by that Base, and Human Life then becomes truly, as it should be, the reflection of the Divine. One more glance through the Window at what I will call-- "The Mystery of the Apex."