Many people are convinced that reincarnation, called gilgul in Hebrew, has been accepted as a fact since ancient times. Reincarnation is the belief that when people die they are transported into a new body in another life. This is not true about Judaism. Gilgul entered Judaism for some mystical-minded Jews only in the Middle Ages.
I will summarize some scholarly ideas about the Jewish view and follow them with my ideas.
In her 2001 Ph.D. Thesis, “The Soul and Afterlife in Jewish Mysticism and Gnosticism,” Dr. Dina Ripsman Eylon gives us the origin of the notion of reincarnation in Judaism. It is available on Academia.edu.
Among much else, she informs us that the twelfth-century kabbalistic work Sefer Bahir, which means “Book of Clarity,” is the first book that introduces the theory of reincarnation as a Jewish theological theory. It is an anonymous mystical work attributed to a 1st-century rabbinic sage Nehunya ben HaKanah because it begins with the words, “Rabbi Nehunya ben HaKanah said.” It is also known as the Midrash of Rabbi Nehunya ben HaKanah.
The book explains the mystical significance of many items. These include biblical verses, the shapes of the Hebrew letters, the biblical cantillation signs and vowel points added to the letters, the earlier mystic book Sefer Yetzirah, the use of sacred names in magic, and it introduces the idea of reincarnation.
Gershom Scholem, the renowned scholar of Jewish mysticism, dated Bahir’s composition to 1176 and said the book enormously impacted Jewish thought. But not every scholar agrees with his dating of Bahir. Some date it later. Some assert that the doctrine of reincarnation was not in the original version of Bahir. They claim that different publishers changed and added to the original, even frequently. What is certain is that while other religions and cultures may have accepted the notion of reincarnation as a fact, Judaism did so only when it was introduced in Bahir. There is no hint of it in the Torah, Talmuds, and early Midrashim.
Rational thinking Jews rejected the idea that humans lived former lives. Mystical thinkers such as the Greek Plato (circa 428-347 BCE) and the Jewish Nachmanides (1194-1270) accepted it. However, the Greek Aristotle (384-322 BCE) and the Jewish Maimonides (1138-1204) rebuffed the idea.
Dr. Eylon recognizes that Jews may have taken the concept of reincarnation from non-Jews. She adds that some Jews were able to accept the notion because they had already adopted that souls exist, a belief that is also not in the Hebrew Bible. Philo (25 BCE-50 CE) was the first Jewish philosopher to introduce the idea that there is such a thing as a soul that exists separate from the body. It contains the intellect and personality of a person. Platonic theories influenced him. He considered the soul to be eternal. However, he did not have the belief in reincarnation. The soul remained somewhere in limbo until the messianic age when it would be revived.
Neither Aristotle nor Maimonides decided that there is a soul. Aristotle wrote that the intellect was part of the body. Nothing on earth disappears. It is often transformed into something else. The body is transformed and absorbed into the world, but the intellect goes elsewhere. Maimonides agreed with him.
Why did many people accept that reincarnation happens?
We do not know. However, most likely, it is caused by the imperfections in human beings.
Most people know little about their religion. Those who know something only remember what they learned in a Sunday School or several afternoon churches or synagogues a few hours a week. These lessons were what children could absorb, not the truth adults should know.
Many learned about their religion by listening to the radio or TV preacher who was more interested in their money than in their education or to rabbis who taught interesting but untrue homiletical Midrashim in their sermons as facts.
Others saw a bearded, saintly-looking man saying what he claimed was wisdom and believed it because of his beard or piety.
Still others accepted teachings that were not rational, such as, “You need to take a leap of faith,” and took no time to translate it as “If you find a religious thought to be illogical, you should accept it anyway.”
Or they swallowed the belief that people are reincarnated from one body to another and never die because it makes them, like many other people who dislike or fear the thought that there is no life after death, feel better. They will exist even after they die, albeit in a different body, without recollecting the past.
Additionally, reincarnation is a convenient explanation of why righteous people suffer. They are punished for misdeeds they committed in a prior life. It also explains why many evil people prosper. They are rewarded for the good they did in a former life.
So, for many rational people, reincarnation is untrue.