It is widely recognized that Abraham was the progenitor of Judaism, Christianity and Islam. What is less known is that the Torah also suggests that he sowed the seeds of what would eventually become the eastern religions as well. Late in his life (and after his wife Sara's death) he married another woman named Keturah and had several children with her as is outlined in Genesis 25. In that chapter there are some interesting nominal correspondences between the children's names and deities of the Hindu pantheon. For instance, one child is named Yokshan which shares the same roots (KSHN) as Krishna and a grandchild is called Shiva. Beyond that, Abraham's name itself shares roots (BRM) with the name Brahma, the Hindu god of creation and the "great grandsire of all human beings." Abraham's wife was Sara and Brahma's is called Sarasvati. While this is obviously not conclusive, it is intriguing grist for the mill.
The text in 25:5 tells us that "Abraham gave all that he had to Isaac. But to the concubine-children who were Abraham's, Abraham gave gifts; then he sent them away from Isaac his son, while he was still alive, eastward to the land of the east." The classical commentators wonder at this; if he had already given "all that he had" to Isaac, what were these gifts that he gave the (soon to be) eastbound children? The indispensible 11th Century elucidator Rabbi Shlomo Yitzchaki (Rashi) explained that he gave them spiritual gifts -- knowledge that they would need for their journey. It's possible that this is the common origin of Judaism and the East's shared belief in reincarnation.
The great Italian Kabbalist Moshe Chaim Luzzato (Ramchal) explained in his classic work The Way of God that "a single soul can be reincarnated a number of times in different bodies, and in this manner, it can rectify damage done in previous incarnations. Similarly, it can also achieve perfection that was not attained in its previous incarnations." Though a full treatment of the logical implications of this idea is not possible in a blog post, this would help to explain the classical existential question of why bad things happen to good people (and vice versa). Jews believe that a human being at his or her core essence is a consciousness, one that transcends the corporeal self. In this light, the human experience is painted on a vastly larger canvas than we currently imagine and has a critical bearing on who we are. One way of exploring this idea is through the following metaphor: You have an axe. It gets a nick in the head so you have it replaced. Then, the handle breaks, and you replace that. Is it the same axe? I once saw a Hare Krishna display in Central Park that illustrated the same idea. It was a small model of a single human life cycle from infancy to old age. "Look at these bodies" the guy explained to me, "do they look related?" "What maintains their continuity?" Biologically speaking we don't inhabit the same container for the duration of our lives as most of our cells fully replicate about every 10 years. If our consciousness can endure a series of shifting bodies then perhaps it can leap from one to another.
Rabbi Isaac Luria's Book of Incarnations is a fascinating exploration of the soul roots of many of the key figures of the Torah. It demonstrates how seemingly unrelated events and people in classic Biblical accounts are actually the same (albeit) reincarnated souls back to take a second crack at achieving their potential or to rectify their poor choices and the negative consequences from previous incarnations. For example, though Noah was considered a righteous man, he is faulted for failing to take responsibility for his generation and allowing them to be destroyed by the flood. The Hebrew word for the boat he built (and that saved humanity) is "teyva." This word is only used one more time in the Torah and it also involves being saved from the water. It's the name given to the little raft that Moses' mother made to hide him from the Egyptians. According to Rabbi Luria, Moses is the soul of Noah who's been offered a second chance to take responsibility for his people and the unusual word is the hint that links the accounts. (This particular soul succeeds with flying colors in round two).
The concept of reincarnation also motivates various aspects of Jewish law, prayer and ethics. Ultimately we believe that good deeds should be performed with no ulterior motive. Nonetheless, it's understood, for instance, that if we transgress the Torah's prohibition against bearing a grudge, (Leviticus 19:18) we might be dragged into someone else's next incarnation to give them the chance to do right by us. To prevent that need there is a wonderful nightly meditation that guides us towards forgiveness of all who may have wronged us that day. It reads (in part) "Master of the Universe, I hereby forgive anyone who angered or antagonized or sinned against me -- whether against my body, my property, my honor or against anything of mine...whether through speech, deed, thought or notion; whether in this transmigration or another transmigration."
Just as Israel geographically stands at the threshold of Europe and Asia, so do its tenets. There is a surprising amount of similarities between Judaism and the spiritual disciplines of the east, including a "shakra" system, a meditative tradition and the aforementioned belief in reincarnation. Through the study of the more esoteric elements of the Jewish tradition, more and more people are discovering the overlap, finding meaning in it and embracing a crucial part of their heritage that has been deemphasized for far too long.