Book of Optics and experiment as argument
A medieval Arabic treatise on optics in seven books in which vision is explained by light travelling from the object into the eye rather than by rays leaving the eye. Each part of the object corresponds to a point on the eye's surface.
Its author, Ibn al-Haytham, worked in Cairo around 1030. The method here matters more than the conclusion: claims about light are tested with purpose-built experiments using the camera obscura, tubes and screens. It is an early example of 'experiment as argument' and not only as illustration.
Through the Latin translation De aspectibus (before 1200) the book became the basis of the optics of Roger Bacon, John Pecham and Witelo, and in Risner's 1572 edition it was read by Kepler.
Why this date
approximate: Sabra's and Smith's dating from internal cross-references; the popular '1011-1021' (the supposed house arrest in Cairo) is not supported by the scholarly editions
What it grew from
-
The Graeco-Arabic translation movement in Baghdad
influenced · Confidence: high
Ibn al-Haytham's Book of Optics stands on the Greek corpus that the translation movement supplied: he knew Ptolemy's Optics thoroughly in Arabic and used it as the guide for his own analysis of vision, so that his book is to a large extent a revision and elaboration of Ptolemy.
Dispute: The link runs through texts, not through an institution or a city. Ibn al-Haytham wrote the Book of Optics in Cairo under the Fatimids, a thousand miles from Baghdad and a century and a half after al-Ma'mun; all they shared was the Arabic corpus of Greek science. Who translated Ptolemy's Optics into Arabic, and when, is not firmly established: the Greek original is lost and the text is known through a Latin translation made from the Arabic.
Link sources
- Smith A. M. «Optics to the Time of Kepler», Encyclopedia of the History of Science (ETHOS), Carnegie Mellon University Libraries (2022) Verified 20 Sep 2026
during the Abbasid Caliphate, which acceded in 750 and took Baghdad for its capital, growing interest in foreign scientific and philosophical texts impelled high-level patrons to commission translations of them
- Smith A. M. (2022) Verified 20 Sep 2026
by the end of the ninth century a sizeable compendium of Greek works had been rendered into Arabic
- Smith A. M. (2022)
Ibn al-Haytham was thoroughly familiar with Ptolemy's Optics and used it as a guide for his own analysis of vision. To a great extent, in fact, the Kitāb al-Manāẓir represents both a thorough revision of, and a grand elaboration on Ptolemy's Optics.
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- Smith A. M. «Optics to the Time of Kepler», Encyclopedia of the History of Science (ETHOS), Carnegie Mellon University Libraries (2022) Verified 20 Sep 2026
What grew out of it
-
The retinal image and the theory of lenses (Ad Vitellionem paralipomena)
influenced · Confidence: high
Kepler wrote the book as a supplement to Witelo, responding to Risner's edition of 1572 in which Witelo's Perspectiva was printed together with Ibn al-Haytham's De aspectibus, and his theory of the retinal image grew inside that perspectivist tradition as a solution to the problem of vision which the tradition itself had posed.
Dispute: Historians differ on whether this is continuity or rupture. Lindberg (1976) sees the theory of the retinal image as the culmination of the medieval perspectivist tradition. Smith (2022) stresses the opposite: for Ibn al-Haytham and Witelo the crystalline lens itself senses the rays falling on it along the perpendicular, whereas for Kepler it refracts the light and forms a real image on the retina, so that Kepler undermined the very scheme he formally set out to supplement. The continuity holds on either reading; only its sign changes, continuation of the tradition or rupture with it.
Link sources
- Smith A. M. «Optics to the Time of Kepler», Encyclopedia of the History of Science (ETHOS) (2022) Verified 20 Sep 2026
Whatever the case, it saw its first printing in 1535 and its second in a tandem edition with Alhacen's De aspectibus published by Friedrich Risner in 1572.
- Smith A. M. (2022) Verified 20 Sep 2026
This, most likely, was the edition of Witelo's Perspectiva to which Kepler was responding in the Paralipomena of 1604.
- Smith A. M. (2022) Verified 20 Sep 2026
In doing so they brought Alhacen into the mainstream of medieval and Renaissance optical thought.
- Richards R. J., Lindberg D. C. «Theories of Vision from Al-Kindi to Kepler», Journal of the History of the Behavioral Sciences, 380 (1979), 380 Verified 20 Sep 2026
The final chapter of Lindberg's study is devoted to what he regards as the culmination of the medieval perspectivist tradition, Kepler's theory of the retinal image.
- Richards R. J. (1979), 380 Verified 20 Sep 2026
Kepler, building on the views of Witelo, Pecham, and Porta, came to appreciate the refractive use of the lens in forming an image on the retina.
- Norton S. D. «Abu 'Ali al-Hasan ibn al-Hasan ibn al-Haytham», Science and Its Times (Encyclopedia.com) (2001) Verified 5 Oct 2026, quotation assembled from fragments
the most important and influential work on optics between the time of Ptolemy...and Johannes Kepler
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.
- Smith A. M. «Optics to the Time of Kepler», Encyclopedia of the History of Science (ETHOS) (2022) Verified 20 Sep 2026
-
Tanqih al-manazir: a revision of the Book of Optics and an explanation of the rainbow
improved · Confidence: high
Al-Farisi's Tanqih is essentially a revision of Ibn al-Haytham's Book of Optics, written after a deep study of it.
Link sources
- O'Connor J. J., Robertson E. F. «Kamal al-Din Abu'l Hasan Muhammad Al-Farisi», MacTutor History of Mathematics Verified 4 Oct 2026
Al-Shirazi advised him to consult the Optics of ibn al-Haytham and al-Farisi made such a deep study of this treatise that al-Shirazi suggested that he write what is essentially a revision of that major work.
- Russell G. A. «Fāresī, Kamāl-al-Dīn», Encyclopaedia Iranica, vol. IX, fasc. 3, 1999 (1999) Verified 4 Oct 2026
critical revision of Ebn al-Hayṯam’s Ketāb al-manāẓer
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- O'Connor J. J., Robertson E. F. «Kamal al-Din Abu'l Hasan Muhammad Al-Farisi», MacTutor History of Mathematics Verified 4 Oct 2026
Node sources
- Smith A. M. «Alhacen. A Critical Edition», Preface (2001) Verified 5 Oct 2026
Sometime between 1028 and 1038, Ibn al-Haytham completed his monumental optical synthesis, Kitab al-Manazir (»Book of Optics«).
- Smith A. M. (2001) Verified 5 Oct 2026
By no later than 1200, and perhaps somewhat earlier, this treatise appeared in Latin under the title De aspectibus.
- El-Bizri N. «Ibn al-Haytham: An Introduction», Muslim Heritage (FSTC) Verified 5 Oct 2026
composed in seven books, sometime between 1028 and 1038
- Norton S. D. «Abu 'Ali al-Hasan ibn al-Hasan ibn al-Haytham», Science and Its Times (Encyclopedia.com) (2001) Verified 5 Oct 2026, quotation assembled from fragments
the most important and influential work on optics between the time of Ptolemy...and Johannes Kepler
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.
Further reading
Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.