THE ORIGIN OF LETTERS AND NUMERALS.

The factorials A factorial is the product of all whole numbers from 1 up to a specific number. In the context of this book, it is used to calculate how many different ways a set of letters can be rearranged. up to that of 12 are as follows:

The factorials up to 36 are given in Rees' Encyclopedia A massive 45-volume universal dictionary of arts, sciences, and literature published in the early 19th century., under the article Cipher. The Mishnah Here referring specifically to the sections of the Sefer Yetzirah (Book of Formation) written in the style of the Mishnah, the first major written collection of Jewish oral traditions. treating of permutation The different ways a set of items or letters can be ordered or arranged. was well explained by all commentators, especially by S. Donnolo Shabbetai Donnolo (913–c. 982), a Jewish-Italian physician and astronomer who wrote an important commentary on the Sefer Yetzirah..

W. Stanley Jevons William Stanley Jevons (1835–1882) was an influential English logician and economist. on the subject of permutation says⁷):

"Thus the letters A, B, C, will make different permutations according as A stands first, second or third; having decided the place of A, there are two places between which we may choose for B; and then remains but one place for C. Accordingly, the permutation of these letters will be altogether 3 x 2 x 1 or 6 in number. With four things or letters A, B, C, and D, we shall have four choices of places for the first letter, three for the second, two for the third, and one for the fourth, so that there will be altogether 4 x 3 x 2 x 1, or 24 permutations. The same simple rule applies to all cases; beginning with the

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⁷) The Principles of Science, London 1887, 178, 179.