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The optics of Ibn al-Haytham: Books I-III, On Direct Vision.

The text of Ibn al-Haytham's Optics, known to the medieval Latin West under the title of Perspectiva or De aspectibus, and whose Latin translation was first published by Friedrich Risner in 1572 A.D., is undoubtedly the most important text on medieval optics. Its importance stems from the fact that it explained for the first time the proper manner in which we see objects, and also represented a spirit most exemplified by Ibn al-Haytham himself, who dealt with classical scientific authority on the most critical basis. Unlike the other text of Ibn al-Haytham, his al-Shukuk ala Batlamyus (Dubitationes in Ptolemaeum), which contained the most cogent criticism of Ptolemy's Almagest, Planetary Hypothesis, and Optics, but offered no alternatives to the sciences of antiquity discussed in these books, this work is devoted to a reconstruction of the science of optics. It is not surprising therefore that, once it was made available in a Latin translation, Ibn al-Haytham's Optics became the most popular reference text for all subsequent works on optics, and was one of the earliest books to be printed on the subject.

But despite its fame and sophistication, this work of Ibn Al-Haytham still remains inaccessible in its totality to English and Arabic readers alike, in spite of the efforts of Sabra, who produced the volume under review as well as the Arabic edition on which it is based. This does not mean that a small circle of historians of science did not know about it. Note the most detailed technical commentary written about it by Mustafa Nazif (2 vols. [Cairo, 1942-43]), listed with full details in the bibliography appended to the second volume of the present text.

The text under review is a translation (vol. 1), with commentary and notes (vol. 2), of the Arabic edition published in one volume by A. I. Sabra, six years earlier, in the Arabic Heritage Series of The National Council for Culture, Arts and Letters of Kuwait. As is stated on both the Arabic and English covers, this text includes only the books (maqalas) relating to direct vision, namely, maqilas I, II and III of the original Kitab al-Manazir of Ibn al-Haytham, which was composed in seven books. In a sense, the present translation, like the earlier edition, should be considered as work in progress, awaiting the production of the full text of Ibn al-Haytham on Optics. The contents of maqalas IV-VII, dealing with reflection, images, mistakes of vision due to reflection and their causes, and vision through refraction from behind transparent bodies, are only excerpted in the Arabic edition (pp. 34-36), where at least the titles of the chapters are given. These remaining maqalas are not treated in the same fashion in the English translation and commentary, where only a very brief comparison of their contents with the Optics of Ptolemy is given (vol. 2, p. lxi). For the English reader, the contents of the first three books are treated in detail, both in the translation and the commentary, but cannot be appreciated in relation to the whole book, for the detailed contents of the remaining maqalas are missing. Therefore, readers of the Arabic as well as the English versions, who are interested in the full text of Ibn al-Haytham, i.e., a text including maqalas IV-VII, still have to resort to the extant manuscripts which are not always easy to obtain. This is indeed unfortunate.

This failure to make accessible a complete text of Ibn al-Haytham's Kitab al-Manazir is unfortunate, especially, because many of the topics discussed in the first three maqalas, fascinating as they are, would not even figure among the subjects studied by a modern student of optics. On the other hand, such a student would be more likely to consider the phenomena discussed in the last four maqalas as appropriately belonging to his discipline, despite the fact that he would nowadays treat the subjects in a slightly different manner. Thus, the only issues recognizable by the modern student of optics are included neither in the Arabic edition nor in the English translation of the first three magalas of Ibn al-Haytham, and still wait to be edited and translated.

To illustrate this point, the first three maqalas deal with the problems of direct vision, i.e., vision unhampered by reflection, refraction and the like. The topics range over such issues as the nature of sight and vision (including a full discussion of the instrument of vision, the eye) (maqala I); problems of perception of light and color, distance, position, shape, number, etc. (maqala II); and errors of direct vision and their causes (maqala III). In the second maqala, even such issues as "beauty" and "ugliness" are discussed in their relation to vision, while in the third, Ibn al-Haytham discusses such topics as the ways in which sight errs either in pure sensation or in recognition. While it is true that the treatment of "beauty" by Ibn al-Haytham is, according to Sabra, "the longest discussion of visual beauty in Arabic [some 2,700 words] from an exclusively aesthetic point of view," nevertheless it is not among the topics that a modern student of optics would commonly expect. Incidentally, size is among the criteria of beauty, and "that is why the moon is more beautiful than any one of the stars," and "shape produces beauty, and thus a crescent moon looks beautiful." The treatment of ugliness, on the other hand, occupies a much smaller space (some 150 words only), and is more or less defined by negation as the "form from which all beautiful properties are absent."

The commentary in volume 2 is a veritable treasure, for it includes detailed, section-by-section, at times even paragraph-by-paragraph, commentaries on important topics or technical concepts. Individual concepts, like the concept of beauty just cited or the reliability of vision discussed in the introductory part to Book III, as part of general Islamic intellectual history, are at times given full treatment, reminiscent of medieval commentaries where the authors took such occasions to publish their articles on the individual subject under discussion. In the same volume, the Arabic-Latin and the Latin-Arabic glossaries, each arranged according to the order of the relevant alphabet, are veritable gems for scholars studying the transmission of Arabic optics to the Latin West, or who are concerned with the roots of the concepts used in the Latin optical tradition. But these glossaries, as well as the concordance relating the Arabic text, with its English translation, to the Latin text published by Risner, were already included in the Arabic edition and are obviously repeated here to increase their utility. Finally, the system of reference to the original manuscripts and the paragraph numbers, maintained in the Arabic edition and the English translation, make the task of double-checking individual words a veritable pleasure, free of the pain usually associated with such an exercise.

By treating the first three maqalas on their own, as an independent unit, Sabra deprived himself of a real evaluation of the background of Ibn al-Haytham's optics in general, and the position his complete work on optics occupies within the history of Arabic optics. This has become more interesting in light of the new findings of Roshdi Rashed in the works of Abu Sad al-Ala Ibn Sahl (fl. 984 A.D.), reported recently in ISIS 81 (1990): 464-91. This Ibn Sahl had successfully treated the phenomenon of double refraction in a sphere, which led him to treat the subject of lenses, and allowed Kamal al-Din al-Farisi (d. 1320 A.D.) to uSe his methods to explain the phenomenon of the rainbow. Ibn al-Haytham falls in between those two figures and was obviously interested in the very same problems. But the subject of refraction as a whole is technically treated in the later maqalas of Ibn al-Haytham, and this must be the reason Sabra did not devote more space to this tenth-century mathematician who was definitely known to and admired by Ibn al-Haytham. To be fair, Sabra does mention Ibn Sahl in two places in the commentary, but in a slightly different context, namely, a discussion regarding the transparency of the celestial sphere. He never mentions him again. Nor does he mention the relevant On the Burning Mirrors, a work by the ninth-century philosopher al-Kindi (mentioned by Rashed). Furthermore, Sabra does not give the earlier mathematicians working on problems of optics as much space as he gives to the successors of Ibn al-Haytham, such as Kamal al-Din al-Farisi. There is no section in the commentary, moreover, devoted to Ibn al-Haytham's predecessors, for example.

As stated above, since these subjects of reflection and refraction, treated by the earlier mathematicians, technically belong to the later maqalas of Ibn al-Haytham's Optics, one can still hope that the future commentary, which will undoubtedly accompany the remaining maqalas, will give these predecessors their deserved place in the history of Arabic optics, if for no other reason than to recognize the real significance of the gigantic leap made by Ibn al-Haytham in his own Optics.

On the technical side, the production of this translation and commentary exhibit once more the care and labor that has gone into this magnum opus. Most of the mistakes that had crept into the Arabic text have now been corrected in the translation, but no list of them is given here for the benefit of the Arabic reader to correct the edition. Luckily, they are only a few, and the hope is that a list of such corrections will be given in the final version of the full edition.

To conclude, one may say that the appetite of historians of Arabic and Latin science has been duly whetted. We can only hope that the rest of Ibn al-Haytham's book is not too long in coming.
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Title Annotation:2 vols.
Author:Saliba, George
Publication:The Journal of the American Oriental Society
Article Type:Book Review
Date:Jul 1, 1992
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