There is no way of fixing the Precise date of this treatise; but it falls among his later ones, perhaps among the latest; the most important hint we get from Ghazzâlî himself being that the book was written after his Magnum opus, the Ihyâ'al Ulûm (p. ). Other works of Ghazzâlî mentioned by him in this treatise are the Mi`âr al-`Ilm, Mahakk al-Nazar, and al-Maqsad al-Asnâ.
The object of the opuscule is to expound a certain Koran verse and a certain Tradition. The former is the celebrated Light-Verse (S. 24, 35) and the latter the Veils-Tradition. It is divided into three sections, of which the first is considerably the longest.
In this first section he considers the word "light" itself, and its plural "lights," as applied to physical light and lights; to the eye; to the intelligence (i.e. intellect or reason); to prophets; to supernal beings; and finally to Allah himself, who is shown to be not the only source of light and of these lights, but also the only real actual light in all existence.
In the second section we have some most interesting prolegomena to the whole subject of symbolic language in the Koran and Traditions, and its interpretation. Symbols are shown to be no mere metaphors. There is a real mystical nexus between symbol and symbolized, type and antitype, outer and inner. The symbols are infinitely numerous, very much more numerous than those mentioned in Koran, or Traditions. Every object on earth "perhaps" has its correlative in the unseen, spiritual world. This doctrine of symbols reminds us of the Platonic "ideas" and their earthly copies, and of the "patterns of things in the heavens" and "the example and shadow [on earth] of heavenly things" in the Epistle to the Hebrews. A notable deduction is made from this doctrine, namely, the equal incumbency of keeping the outward letter (zâhir) of the Law as well as its inner meaning (bâtin). Nearly all the most advanced Sûfis were zealous and Minutely scrupulous keepers of the ritual, ceremonial, and other prescriptions of the Sunna law, and Ghazzâlî here supplies a quasi-philosophical basis for this fidelity--a fidelity which some of the bolder and more extreme
mystics found illogical and "unspiritual".
In the third section the results of this symbology are applied to the Verse and Tradition in question. In the former the beautiful, and undeniably intriguing expressions of the Koran--the Light, the Niche, the Glass, the Oil, Tree, the East and the West--are explained both on psychological and religio-metaphysical lines; and a similar exegesis is applied to the tradition of the Seventy Thousand Veils.