How prevalent is the Jewish belief in reincarnation today? How does it differ from the Asian belief? What do the Rabbis think of it?
The root of the word "Torah" is the verb "to instruct". Torah's primary function is to teach us how to live Jewishly, in harmony with G‑d's will. As such, the basic levels of scriptural interpretation lead to a practical understanding of mitzvot and related Jewish values.
Many Jews are surprised to learn, or may even wish to deny, that reincarnation…is an integral part of Jewish belief…
The Torah, however, is a multi-layered document. Many of its deeper levels of interpretation are not readily accessible; and they may not lend themselves to obvious, practical application in daily life. As such, these more esoteric aspects of Torah are not of interest to significant segments of the Jewish population, including some rabbis and scholars.
Consequently, many Jews are surprised to learn, or may even wish to deny, that reincarnation - the "revolving" of souls through a succession of lives, or "gilgulim" - is an integral part of Jewish belief. But this teaching has always been around. And it is firmly rooted in source-verses.
Examples abound. Ramban, one of the greatest commentators on the Torah (and on the Talmud), and a seminal figure in Jewish history, hints several times that reincarnation is the key to penetrating the deep mysteries involved in the mitzvah of yibum (the obligation of the brother of a childless, deceased man to marry the widow). In his explanation of Gen 38:8, he insists that Yehudah and his sons were aware of the secret of reincarnation, and that this was a major factor in their respective attitudes towards Tamar.
lies with us…
The Jewish understanding of reincarnation is different from Buddhist doctrines. It in no way leads to fatalism. At every point of moral decision in his life, a Jew has complete free choice. If not for freedom of choice, how unfair it would be of G‑d to make demands of us - especially when reward and punishment is involved! Reincarnation does not imply pre-determination. It is, rather, an opportunity for rectification and soul-perfection.
The holy Ari explained it most simply: every Jew must fulfill all 613 mitzvot, and if he doesn't succeed in one lifetime, he comes back again and again until he finishes. For this reason, events in a person's life may lead him towards certain places, encounters, etc., in ways that may or may not make sense. Divine providence provides each person with the opportunities he needs to fulfill those particular mitzvot necessary for the perfection of his soul. But the responsibility lies with us. At the actual moment of decision in any given situation, the choice is ours.
One of the ways in which heaven maintains our ability to exercise complete freedom of choice is by not allowing us conscious knowledge of previous incarnations. Consequently, it might seem to some people that there is little practical benefit in being aware of this doctrine. Furthermore, many scholars contend that these mystical concepts can easily be misunderstood, or carried to erroneous and misleading conclusions. We can therefore understand why this and similar subjects are only hinted at in scripture, and why some knowledge and a great deal of determination are often required in order to gain access to this information.
For an in-depth English treatment of the Jewish doctrine of reincarnation, see the running translation and commentary of Shaar Gilgulim on KabbalaOnline.org. (For the first article in the series, "Gate of Reincarnations", click here).
(Also, the English edition of "Derech Hashem" by Rabbi Moshe-Chaim Luzzatto, "The Way of G‑d", translated by Aryeh Kaplan (Feldheim, 1983), II:3:10 (page 125) plus notes 39-40 (pp. 342-3) provides an English list of Torah sources on this topic in both scripture and Kabbalah.)