This small book is in no sense a treatise on the Qabalah. Instead, it is a speculative study on one of several secret doctrines which it contains, and, I believe, the key-doctrine of all the others. Should this be correct, then it follows that, unless this doctrine is understood, the whole symbolism of Jewish mysticism must remain obscure, and it is this mysticism, so it seems to me, which constitutes the foundations of Jewish culture and Jewish aspirations...