Connected Histories

The Impact of Alhazen's Optics on How We See the World

About This Resource

Al-Hasan ibn al-Haytham (Latin name, Alhazen) (d. 1040 CE), scientist, copyist and teacher, was famous during the European Renaissance as an innovative scientist in the field of physics, and especially optics—the theory of vision. His major work Kitab al-Manazir (The Book of Vision), overcame the Greek notion that human sight resulted when the eyes projected rays onto objects. Ibn Haytham combined experiments on the behavior of light and optical illusions with geometric proofs, and his calculations and diagrams aided in making accurate magnifying lenses. The Latin translation of his work on optics and his critique of Ptolemy influenced medieval European scientists like Roger Bacon in developing the scientific method. The Book of Vision was printed in Basel in 1572, and it influenced mathematicians such as Kepler, Descartes, and Huygens.The image on the left shows proofs and diagrams from the Arabic translation of the Conics of Apollonius, transcribed and drawn by Ibn al-Haytham himself. On the right is an engraving from the frontispiece of Selenographia, a 1647 description of the moon by Johannes Hevelius, showing Ibn al-Haytham and Galileo as two scientists who explored nature by means of rational thought. Ibn al-Haytham holds a geometrical diagram representing Reason, and Galileo holds a telescope respresenting Observation, both approaches to knowledge being keys to scientific discovery.  The excerpt from Ibn al-Haytham’s work describes his attitude toward received knowledge and contribution to the scientific method.


"Truth is sought for itself"—but "the truths...are immersed in uncertainties [and] not immune from error...Therefore, the seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. Thus the duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency."


Sabra, Abdelhamid I. “Ibn al-Haytham | Harvard Magazine Sep-Oct 2003.” Image credit: Photomontage by Bartek Malysa. Frontispiece courtesy of the Department of Printing and Graphic Arts, Houghton Library, Harvard College Library (Typ 620.47.452F) of MS Aya Sofya, no. 2762, Aya Sofya library, Istanbul.

How to Cite This Page

"Muslim Journeys | Item #173: The Impact of Alhazen's Optics on How We See the World", January 17, 2018


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