A 13th-Century Algorithm for Permutations Ignored for 700 Years

A 13th-Century Enumeration Algorithm, Ignored for 700 Years

While researching the Kabbalist Abraham Aboulafia, I discovered a systematic method for enumerating all permutations of letters. This 13th-century spiritual practice actually describes a recursive algorithm that predates modern computer science by seven centuries. Aboulafia's elegant rule, which rotates letters to generate every possible arrangement, was the only such method known until English change-ringers developed a similar approach three hundred years later.

"This rule is easy to understand; and though it has no end that we can grasp, it necessarily has an end."