Since the profound wisdom of the holy Zohar is locked behind a thousand doors, and our tongue too meager to elucidate indeed not one issue in this book, I have written this foreword, which is but a ladder to help one reach the stature of the things discussed and contemplate upon the words of the book itself. Therefore, I have found it necessary to provide the reader with a true idea as to how to educate oneself through this book.
First, one must bear in mind, that all the Zohar speaks of, even when it speaks in fables, is but ten spheres, known as Keter, Chochma, Bina, Chesed, Gvura, Tifferet, Netzach, Hod, Yesod and Malchut and their interactions with one another. Much like the twenty two letters of the hebrew alphabet, so the entries and their various combinations are sufficient to disclose the entire wisdom in this book of heaven.
Rabbi Yehuda Ashlag (Baal HaSulam)