Sometime between 1028 and 1038, Ibn al-Haytham completed his monumental optical synthesis, Kitab al-Manazir ("Book of Optics"). By no later than 1200, and perhaps somewhat earlier, this treatise appeared in Latin under the title De aspectibus. In that form it was attributed to a certain "Alhacen." These differences in title and authorial designation are indicative of the profound differences between the two versions, Arabic and Latin, of the treatise. In many ways, in fact, they can be regarded not simply as different versions of the same work, but as different works in their own right....