In the large scheme of history, it may be observed that the Jewish people, which grew up and reached a certain maturity in its own land, was in exile for hundreds of years.
And this meant the loss of much more than national sovereignty; whole areas of tradition were abandoned and only vague hints survived in memory.
One can hardly reconstruct the richness of this tradition from the written evidence.
To a degree, the Temple, the legal and social structure, the schools and synagogues can be pieced together in some fashion or other.
The mystical traditions are far more elusive to the modern researcher.
Most of them have been totally wiped out by time, such as the schools of the prophets.
We have nothing resembling such schools, either in Israel or in the Diaspora.
In fact, there are been attempts to make such a restoration by pasting scattered indications together.
Some of this material has survived only in written form; most of it is considered irretrievably lost.
Nevertheless, the dream or hope or restitution has remained.
In the days to come, a regeneration is possible, if the right stimulant appears.
This anticipation is possible because, as in every organic entity, the code of the whole is contained in the fragments, so that from the little that has come down to us it may be possible to reconstruct a semblance of the ancient tradition.
–Rabbi Adin Steinsaltz
From "After the Bright Light of Revelation: A Conversation with Rabbi Adin Steinsaltz" from Parabola Magazine.