The "Sepher Yetzirah," although this name means "The Book of Formation," is not in any sense a narrative of Creation, or a substitute Genesis, but is an ancient and instructive philosophical treatise upon one aspect of the origin of the universe and mankind; an aspect at once archaic and essentially Hebrew. The grouping of the processes of origin into an arrangement, at once alphabetic and numeral, is one only to be found in Semitic authors.Attention must be called to the essential peculiarity of the Hebrew language, the inextricable and necessary association of numbers and letters; every letter suggesting a number, and every group of letters having a numerical signification, as vital as its literal meaning.The Kabalistic principles involved in the reversal of Hebrew letters, and their substitution by others, on definite schemes, should also be studied and borne in mind.It is exactly on these principles that the "ground-work idea" 'of this disquisition rests; and these principles may be traced throughout the Kabalistic tractates which have succeeded it in point of time and development, many of which are associated together in one volume known as the "Zohar," which is in the main concerned with the essential dignities of the Godhead, with the Emanations which have sprung therefrom, with the doctrine of the Sephiroth, the ideals of Macroprosopus and Microprosopus, and the doctrine of Re-incarnation.The "Sepher Yetzirah," on the other hand, is mainly concerned with our universe and with the Microcosm. The opinions of Hebrew Kabalistic Rabbis and of modern mystics may be fitly introduced here. The following interesting quotation is from Rabbi Moses Botarel, who wrote his famous Commentary in 1409:--"It was Abraham our Father--blessed be he--who wrote this book to condemn the doctrine of the sages of his time, who were incredulous of the supreme dogma of the Unity. At least, this was the opinion of Rabbi Saadiah--blessed be he--as written in the first chapter of his book The Philosopher's Stone. These are his words: The sages of Babylon attacked Abraham on account of his faith; for they were all against him although themselves separable into three sects.