Henry Corbin was a French scholar of philosophy and religion, often regarded as a follower of the Traditionalist school associated with René Guénon. Corbin was particularly interested in the mystical and esoteric sides of Shia Islam. He is also notorious for being very hard to read, although Guénon is probably even worse!
In this book, Corbin offers an extensive exegesis of 18th century Swedish mystic Emanuel Swedenborg's teachings. He then relates them to strikingly similar teachings found among Shia Muslim mystics and esotericists. Corbin's point is *not* that Swedenborg was somehow influenced by Shia Islam, but rather that we are dealing with an objective spiritual reality which therefore appears in more or less the same manner to those capable of perceiving it. On the purely historical plane, Corbin believes (I think!) that Shia esotericism is indebted to both Zoroastrian angelology and Neo-Platonism, representing a kind of fusion of both strands, expressed in Muslim garb. It's less clear whether Corbin regards Swedenborg as influenced by earlier thinkers, but he does mention Boehme. But, as already mentioned, Corbin regarded the spiritual realities described by “Gnostic” mystics as real, which makes his scholarly works simultaneously theological in character.
I admit that I didn't find the first essay in this book that difficult to comprehend, but that's mostly because I've been reading similar-sounding books for several years (and no, I didn't get half of it at first try). If you have successfully assimilated Patrick Harpur's “Daimonic Reality”, Owen Barfield's interpretations of Coleridge and Steiner, and perhaps some Steiner and Emerson, this will strike you as familiar territory. A very good knowledge of Western esotericism in general might also be of assistance. Somewhat ironically, a working knowledge of Guénon and other Traditionalists doesn't help much when reading Corbin, the latter having his own distinct style and (perhaps) agendas.
Here are some of the issues discussed in this book, with Swedenborg's teachings as the immediate context. Corbin believes that there is an “imaginal sense” different from mere imagination or fancy. The imaginal sense, which only exists in some humans, is what makes knowledge of heavenly realities possible. This sense corresponds to the imaginal world, which is both similar and different from what modern occultists call “the astral world”. The visions of this plane of existence shouldn't be taken absolutely literally, but they aren't entirely subjective either. Rather, they are a kind of symbols of even higher realities. It's interesting to note that both Swedenborg's and Rudolf Steiner's visions sound weirdly literal and are often interpreted that way by both friend and foe, while both visionaries apparently believed that their visions were “translations” of spiritual realities not easily rendered in human language.
Corbin then discusses the various levels of reality (celestial, angelic and terrestrial), and argues that humans live in all three at once. The physical reality, often interpreted as “external”, is really “internal” in the sense of being encompassed by the spiritual spheres. Human bodies have the same three-fold structure. Corbin believes that communication between humans and God is made possible through (literal!) angels, and that the Platonic forms are really personal angelic beings (compare “The Place of the Lion” by Charles Williams). Another important concept concerns correspondences between material realities and spiritual ditto. These are discernible only to the mystic, although all humans had the ability to see the spiritual dimension before the fall. Interestingly, Corbin doesn't believe that pre-fall humans were of pure spirit, rather their physical bodies (and the physical reality surrounding them) was subsumed under the spiritual reality, humans constantly seeing material objects under their spiritual aspects. (This is at least somewhat similar to interpretations of Eden in Eastern Orthodoxy.)
In the second and more difficult essay, Corbin tackles the interpretation of Scripture. Just like reality itself, the Bible has several different levels, and the esotericist naturally goes behind the purely literal sense to discern its spiritual meaning. The doctrine of correspondences signifies that every event described in the Bible (say, the Deluge or the Exodus) has its spiritual counterpart, which is more important. Besides, many events described in the scriptures are purely symbolical even on “our” level. Corbin believes that the literal meaning of Scripture both reveals and conceals the esoteric meaning: to the man of spiritual discernment, the Bible is a revelation of spiritual truths, but to most people, the literal text instead hides them. The Catholic Church believes that the Biblical text has several levels of meaning, but Corbin and Swedenborg take this further, since the spiritual meaning often directly contradict the plain meaning (for instance, the Apocalypse isn't a literal event). It's not clear what objective criterion Corbin can appeal to if two or more seers present different hidden meanings of the same text. Presumably, he believes that we are dealing with a unified tradition that exists in all religions and goes back millennia before Christ, perhaps to Mahayana Buddhism. (When Swedenborg claims that the true message emerged from Central Asia, Corbin for once interprets this as an actual geographical location.)
It's also interesting to note that Corbin emphasizes the need for both the esoteric and the exoteric during the present world cycle (this is the official Shia Muslim position), and that Adam and Eve fell because they wanted to prematurely do away with the exoteric in favor of pure esoterism! (In Shia Islam, the exoteric includes the sharia, which all faithful Muslims are supposed to follow.) The fall can take two forms in Corbin's exegesis: pure exoterism as in Western materialism and its dead science, and libertinage as in antinomian sects which claim to have “the esoteric” or “the spiritual” without any outer propriety.
The latter half of the second essay is the most difficult, dealing with Shia Muslim esotericism, mostly that of the Ismailites. While Corbin's point is that Swedenborg and the Ismailites have the same Gnosis, the worldview and terminology of the latter is so alien to a Western reader, that the whole thing becomes almost incomprehensible. Corbin's speculations on the divine feminine and its diverse incarnations on the physical plane (sometimes as a man!) are particularly hard to grasp, apart from the obvious connection to the heavenly androgyne known from esoteric traditions.
“Swedenborg and Esoteric Islam” is one of the most narrow books I've reviewed here, and I honestly don't know who might be interested in reading it. Perhaps scholars of comparative religion specializing in Swedenborg or Ismailism, respectively. Or some kind of high Gnostic initiates? It does seem to be a text which simultaneously both reveals and hides…