Currently the text exists only in fragmentary form, and scholars have debated how to date it appropriately. Modern academic scholars of Jewish mysticism such as
Gershom Scholem think that it is from “either the Tannaitic or the early
Amoraic period.” However, in the 12th century, the rationalist Jewish philosopher
Maimonides declared the text to be a
Byzantine forgery. Maimonides also believed that the text was so heretical and contrary to proper Jewish belief that it
should be burned.
Saadia Gaon also expressed doubts about the origin of the text, and stated that “since it is not found in either
Mishna or
Talmud, and since we have no way of establishing whether or not it represents the words of Rabbi Ishmael; perhaps someone else pretended to speak in his name.” Nonetheless, in the case that the text were somehow proven to be genuine, Saadia wrote that it would have to be understood in line with his “theory of 'created
glory,'" which explains the prophetic
theophanies as visions not of God Himself but of a luminous [created] substance.”
Moses Narboni also wrote a philosophic work about the text entitled
Iggeret ʿal-Shiʿur Qomah ( "Epistle on Shi’ur Qomah"), wherein he dismisses the blatant anthropomorphisms of Shi'ur Qomah as speaking strictly metaphorically. Rabbi Narboni’s work in the Iggeret is a “meditation on God, Measure of all existing things. It is based on
Abraham ibn Ezra's commentary on
Exodus, and, with the aid of biblical and rabbinical passages, studies two kinds of knowledge: God's knowledge of his creatures, called knowledge of the Face; and His creatures’ knowledge of God, called knowledge of the Back (an allusion to Exodus 33:23).” ==See also==