[Today, on the whole, our knowledge of this higher strata is extremely limited, and this has been the case for many generations. In the distant past, the ranks of Torah scholars were replete with great tzaddikim and gaonim. In those eras we were always privileged to have among us a sprinkling of unique greats who were at home not only in the ocean of revealed Torah knowledge but also in the area of concealed and secret wisdom of Torah, a realm we call kabbalah. This is the subject matter of the Sefer Yetzirah and other books like it. In our times, mastery of these areas is a rarity.
No one can successfully enter the inner chambers of Torah knowledge without first reaching a level of special greatness. That special greatness is shown by the mastery of the conventional, revealed realm of Torah (niglah) which makes one worthy of acquiring the wisdom of kabbalah. Then he must personally be taught this knowledge by a great Torah scholar, one to whom the knowledge was passed down by another living link in the chain of gedolim of previous generations. The chain can be traced back, link by link, to Moshe Rabeinu. It is both ludicrous and dangerous to study kabbalah without first (a) becoming a statured talmid chochom in every area of revealed Torah knowledge and (b) acquiring the qualities which identify the refined and those of perfected character of the highest order. Ludicrous because it is comparable to a man who is prepared to spend years calculating the number of stars in the heavens - to enrich his knowledge of the universe - but (in his own perimeter) he is so ignorant that he has no idea how many teeth make up a set in an adult's mouth. Dangerous because studying kabbalah is like studying a coded book. By mistakenly thinking he has "broken the code," one draws from this study both false assumptions and conclusions. He will attribute to our Torah, concepts, ideas, and theories which are totally foreign to the Torah and which contradict true Torah teachings.
The unprepared man also steps with the muddy boots of unrefined character and minimal Torah knowledge into the holy of holies. People such as this are ejected very quickly. The swift boot down from the heights of the Holy Mountain to the valley below can shatter the frail skeletal structure of whatever Torah accomplishment has been achieved - and leave a spiritual cripple lying at the foot of the Mountain. Such outcomes we see quite frequently in the case of impatient baalei teshuvah who have barely licked the spoon of basic Torah study and go on immediately to kabbalah to do "their own thing" because they either lack or simply reject the proper guidance in their studies.
Those so-called "scholars" who go ahead and teach kabbalah to a baal teshuvah, not withstanding his raw state, are about as reliable and authoritative in regard to their mastery of kabbalah as the average Chinese laundryman is in regard to his qualifications for teaching the Sefer Yetzirah.]