Aleister Crowley's essential book, The Book of the Law, was originally called Liber Legis. Frater Achad (Carl Stansfeld Jones 1886–1950) wrote a small book entitled Liber 31, which revealed important aspects to Crowley's book, especially with the Hebrew word for "no" (spelled Aleph Lamed) that numerologically totaled 31. Crowley was so impressed that he changed the name of his book to Liber Al vel Legis. Today, many Thelemites (followers of Crowley's tradition), refer to the book as Liber Al.

The Hebrew word Al has spiritual meanings in Hebrew, Greek, and Arabic. In Hebrew it is added to the names of some angels to signify they are of God. In the Kabalah it is one of the names of God. It is also used by Muslims as in their name of God, "Allah." As a result, some say it is a way to express the underlying unity of all religions.

Besides changing the title of his book, Crowley came to believe that Frater Achad was his magickal child as predicted in that book. Unfortunately, Achad wrote a book on the Tree of Life that completely rearranged the paths and their corresponding Tarot associations. Crowley objected to this and disowned Achad as his "son."