The answer that was given referred the listener to the popular Muslim conception of Paradise, which is divided into several celestial levels, awarded according to the degree of righteousness achieved during one's mortal lifetime.
That may very well be the channel through which the expression reached English. It should, however, be noted that the concept preceded by many centuries the rise of Islam, and has deep roots in Jewish tradition.
The Seven Heavens
Some of the Rabbis of the Talmud had very precise ideas about the structure of the upper regions. They were presumably influenced by the fact that the Hebrew word for "heavens" or "sky" appears only in a plural form: shamayim, implying a multiplicity of heavens. Given the special role of the number seven in the Bible, it was natural that this number should also determine the arrangement of the heavens.The Jewish sages had no trouble finding distinct functions for each of the seven levels. The heavens, mysterious as they are, affect us in many aspects of our daily life, as well as having important religious associations.
Thus, according to one quaint itemization, one heaven is required simply to screen off the light at night-time, another to store the rain and snow, and still another to house the planets. Others have more religious uses, accommodating the souls of the righteous and the unborn, as well as various levels of angels, the Heavenly Jerusalem, and the throne of God.
According to one legend, the Israelites who assembled at Mount Sinai to receive the Torah were treated to a glimpse of all seven heavens opened up above them.
The Jewish mystical tradition, as it is revealed to us in texts dating from just after the Talmudic period, turned the concept of seven heavenly levels into a key focus of its speculations. According to their imagery these heavens are actually palaces--"heikhalot"--and the task of the mystic is to ascend as high as he can until he reaches the highest level, where he will be vouchsafed a peek at the throne of God.
In this conception of multi-layered palaces the Jewish mystics were influenced by the verse in the Song of Songs (1:4); "The King [i.e. God] has brought me into his chambers," a verse which had already been interpreted allegorically by Rabbi Akiva, the most renowned Talmudic mystic.
The Mystical Ascent
The rules of the mystical ascent into the Heikhalot are quite complex and (as I have had confirmed by my family's 11-year-old expert on the subject) remarkably similar to those of a video arcade game. Throughout his ascent, the mystic is being opposed by hostile angels who stand guard at every gate on the way. The opposition becomes more powerful as the levels get higher.
This type of mysticism also passed into Christianity. The late Gershom Scholem, the leading historian of Jewish mysticism, calls our attention to the testimony of Paul, who describes (2 Corinthians 12:2-4) how he himself had experienced a similar mystical ascent: "Whether in the body or out of it, I do not know--God knows." Paul was caught up as far as "the third heaven," where he "heard words so secret that human lips may not repeat them."
Scholem argues that such climbs through the different levels of heaven were probably common among Jews of the time.
The "third heaven" seems to have been a common stopping-point in the journey, and is mentioned in some Jewish works of the period. The Talmud relates how a group of Rabbis discoursed so impressively about Ezekiel's mysterious vision of the heavenly chariot, that a heavenly voice was prompted to announce: "A place is prepared to you, and a table is set for you--you and your students are admitted to the third level."
Clash With Science
As Jewish thinkers became more familiar with science and astronomy the enumeration of seven heavens became problematic.According to the medieval theory there were at least ten "heavens"--concentric spheres each one containing a heavenly body (the seven known planets, the sun and moon, as well as the outer sphere housing the stars). These heavenly bodies were believed to be "separate intelligences," incorporeal beings of pure thought, who were identified with the angels of the traditional religions.
Maimonides, in his Guide of the Perplexed (composed around 1190), tried to reconcile the apparent discrepancy between the Talmudic description and the science of his day. While asserting that the number seven could if necessary be justified on scientific grounds (since some levels are grouped together), Maimonides argues that the Rabbinic tradition should not be taken literally, but as an allegory about God's guidance of the universe.
Though in a manner very different from the mystics, Maimonides also believed that human beings should strive to experience the higher spiritual levels of the various heavens. To the extent that an individual is capable of contemplating pure, eternal, abstract truth, he can "plug in" to the lowest of the separate intelligences. For the philosopher, such knowledge becomes the ultimate purpose of religious life.
The determination to ascend through the seven heavens has remained alive in more recent times.
The founder of the Hasidic movement, Rabbi Israel Ba'al Shem-Tov, describes in a letter to his brother-in-law how, between 1746 and 1749, he engaged in a number of mystical ascents, including one where he rose higher than ever before to confront the Messiah himself, who answered various questions for him, and provided him with secret charms to facilitate future celestial visits.
Like Jewish mystics from earliest times, the Ba'al Shem-Tov used his heavenly ascent as an opportunity to ask for Heavenly intercession to ward off impending disasters that were threatening the Jews.
The expression "being in seventh heaven" is thus an extremely ancient one in Judaism. Its rich associations make it difficult for me to use the phrase glibly according to its current vernacular usage, as a mere superlative for extreme happiness.
Why Didn't I Learn This in Hebrew School