FRIEDRICH RISNER’S

mathematics, we expected) when Pierre de la Ramée original: "P. Ramus," a famous French humanist and mathematician, having sought it long and hard through various libraries and tracked it by every trace, finally purchased it when it was put up at a public auction and treated as if it were abandoned. Later, having obtained another copy as well, he handed both to me—whom he had held as a partner and assistant in mathematical practice for some years prior—to be compared.

Afterwards, when he had rescued certain mathematical works dearer to him—and this Alhazen in particular—from his library amidst the heat of the recurring wars referring to the French Wars of Religion, he brought me with him to Basel, along with these works as if they were his household gods original: "penates," a reference to Roman protective deities of the home. He spent an entire year occupied in restoring and organizing this author.

Indeed, I discovered a wonderful diligence and learning in this Arabic man, and, as far as I could notice, it was not significantly aided by the ancient opticians of Greece. There is almost nothing here of Euclid or Ptolemy. Perhaps he had taken something from Archimedes, Apollonius, and Auenellus likely referring to a Latinized version of an Arabic scientist, possibly Ibn Mu’adh or similar, by whom certain writings on optics are recorded in literature; likewise from Damianos and other opticians, whose books have not yet fallen into my hands.

Yet Alhazen himself confesses to reading the ancient opticians in Book 6, Chapter 4, regarding the error that occurs in convex spherical mirrors, and in Book 7, Chapter 6, on how sight perceives visible objects according to refraction. Therefore, since I had perceived a writer who was indeed clear and prolific regarding optics, but extremely disorganized, I took up a plan at the suggestion and authority of Pierre de la Ramée, which is as follows:

First, because the whole work was divided into a few lengthy chapters in a continuous and uninterrupted discourse, I distinguished the individual books and chapters into propositions. I also noted which theorems of Witelo original: "Vitellonis," a 13th-century Polish natural philosopher who built upon Alhazen's work corresponded to these, so that by comparing the theorems of both, the subject matter of optics—which is rather difficult and obscure for an unrefined or novice reader—might receive some light and clarity.

Next, I corrected and restored all the demonstrations. I added their foundations and proofs (which were lacking in almost all places) from Euclid, Theodosius, Apollonius, Serenus, and other geometers. Especially in the fifth and sixth books, which comprise catoptrics the study of light reflection, particularly by mirrors, and the seventh, which explains refraction, I attempted to illuminate them with certain short commentaries because of the obscurity and brevity of the demonstrations. Finally, I redesigned the figures for all the propositions from scratch. And here, in the matters and opinions...