Ibn Al-Haytham's Criticisms of Ptolemy's Optics

Notes and Discussions IBN AL-HAYTHAM'S CRITICISMS OF PTOLEMY'S Optics I PTOLEMY'S Optics has survived in a Latin translation made in the twelfth century from an Arabic version of the Greek text. 1 Both the Greek original and the Arabic translation have been lost. Of the five parts (maqaldt: sermones) which the Greek text originally comprised, the extant Latin version has preserved only parts II-IV and a fragment from the beginning of part V. There is no evidence that the first part ever existed in Arabic, and it may have been missing in the Greek text which formed the basis of the Arabic translation. In any case we know that this part was no longer available to Arabic scholars in the eleventh century. This we infer from the title of a work which the mathematician, astronomer, and physicist, Ibn alHaytham , better known in the west as Alhazen (died ca. 1039), wrote before 417 H. (A.I). 1026). The fifth item in an autobibliography including mathematical works which Ibn al-Haytham had composed up to that date, reads as follows: "A book in which I summarized the science of optics (cilm al-manazir) from the two books of Euclid and Ptolemy, to which I added (wa-tammamtuhu) the matters of the first part (maqdla) that is missing from Ptolemy's book." ~Unfortunately, this summary has not survived; nor has another work of Ibn al-Haytham's~ entitled "A treatise on optics according to Ptolemy's method." 3 We do possess, however, a piece of writing by Ibn al-Haytham which is directly concerned with Ptolemy's optical work. This is a brief discussion of Ptolemy's Optics which Ibn al-Haytham wrote some time after the composition of his great work, al-Mandzir? This discussion has not been edited or translated, and it is my aim here to present an English translation of it, based on the edition now being prepared by Mr. Nabil Shih~bi of Alexandria and myself. The discussion is contained in a work whose title suggests the critical vein in which it was written: al-Shukak cala Bat.lamyas (Doubts about Ptolemy). 5 This 1The Latin translation of Ptolemy's Optics was first published by Gilberto Govi, L'Ottica di Claudio Tolomeo . . . (Turin: 1885); then by Albert Lejeune, L'Optique de Claude Ptolbm$e, dans la version latine d'apr~s l'arabe de l'~mir Eugene de Sicile. Texte critique et ex~g~tique (Louvain: 1956). References will be to Lejeune's edition. 2Ibn Abi Usaybiea, "Uyan al-anbd' .... ed. A. Miiller, II (Cairo: 1882), 93-94; F. Woepeke, L'Alg~bre d'Omar al-Khayyam~ (Paris: 1851), pp. 73-74, n ***.A recent attempt to reconstruct the first part of Ptolemy's Optics from available material is to be found in A. Lejeune, Euclide et Ptol~m~e (Louvain: 1948), pp. 15 ft. For new light on the transmission of the fifth part, see note 16 below. 8Ibn Abi U~aybiea, loc. cit., p. 98. The Latin translation ofKitdb al-mandz.ir, made probably at the beginning of the thirteenth century, was published by F. Risner in Opticae thesaurus: Alhazeni libri septem... (Basle: 1572). For Ibn al-Haytham's theory of vision expounded in al-Manazir, see E. Wiedemann, "Zur Geschiehte der Lehre vom Sehen," Annalen der Physik und Che'mie, Neue Folge, Band XXXIX (1890), 470--474;H. Bauer, Die Psycholoqie Alhazens, auf Grund yon Alhazens Optik dargestellt (Mfinster: 1911). 5Listed in Ibn Abi U~aybi~ loc. cir., p. 98, and by Ibn al-Qif~i, Ta'r~kh... , ed. MiiIler and Lippert (Leipzig: 1903),p. 168.For a report on the part of this work dealing with Ptolemy's astronomy, see S. Pines, "Ibn al-Haytham's Critique of Ptolemy," Acres du dixi~me congr~s internationale d'histoire des sciences (Ithaca: 1962), Paris: 1964, I, 547-550. [1451 146 HISTORY OF PHILOSOPHY work consists of a brief introduction explaining the author's aim (viz., to point out the errors which even as great a mathematician as Ptolemy has committed), followed by a criticism of some of Ptolemy's views expressed in three of his works: the Almagest, the...