A 13th-Century Enumeration Algorithm, Ignored for 700 Years
This is the first article in a series about a discovery I made while researching Tserouf in the writings of the Kabbalist Abraham Aboulafia (1240 β after 1291). Tserouf is the Kabbalistic art of permuting the letters β and, in plain mathematical terms, it is the enumeration of all the permutations of an n -letter word.
In Or ha-Sekhel (βThe Light of the Intellectβ), Aboulafia prescribes a systematic method for enumerating all the possible arrangements of an n -letter word. The method is conceived inside a frame of spiritual practice β and yet it carries a mathematical structure of remarkable rigour.
For a three-letter word, Aboulafia gives the Tserouf β the ordering of all six permutations β explicitly:
The words fall into three groups, by their first letter:
Aboulafia explicitly mentions two rules for the Tserouf of 3 letters:
Rule 1 β the mirror. The whole sequence must end on the reverse of where it began . Aboulafia says it plainly: βthe last utterance is the reverse of the first.β The first word is abc ; the last must be cba , its end-to-end reversal.