Who was Alhazen?

Abu ‘Ali al-Hasan ibn al-Hasan ibn al-Haytham (c. 965 – c. 1040), who came to be known in Europe as Alhazen, was a medieval Muslim scientist and philosopher (normally I would prefer to use his Arabic name, but “Alhazen” had a better rhythm for the title of the blog). He is best known for his work in optics and medicine, although he also made contributions to astronomy, mathematics, and biology. More about his biography can be found on Wikipedia and on webpages like this fan page.

Because for the last several centuries the “West” has defined itself, in part, as the true heir to the ancient Greek philosophical and political heritage, it is often easy to forget that most of what had been the Greek-speaking Hellenistic world was absorbed into the Islamic world culturally and intellectually. Alhazen lived during one of the most intellectually vibrant periods of Islamic history. A “House of Wisdom” (dar al-hikma) could be found not only in the ‘Abbasid caliphal capital in Baghdad, but also in the capitals of competing political powers in Cordoba, Spain and Cairo, Egypt. These institutions were dedicated to translating Greek, Persian, and even Indian texts into Arabic, studying them, and advancing the pursuit of philosophy and science beyond the Greek foundations. Europe eventually joined the conversation, leading up to the Renaissance. For a brief period, Muslim, Jewish, and Christian philosophers and theologians were working through some of the same intellectual problems and engaged in one another’s work, such as the place of human rationalistic methods in theologies based on divinely revealed texts.

Ibn al-Haytham’s work on optics treated the subject holistically. He pursued not only the physical questions about the nature and movement of light and the anatomy of the eye but also the psychological and philosophical questions of illusion and perspective. Based on observations from Aristotle and Ptolemy, his best-known experiment came to be known in Latin as the camera obscura, in which an image could be projected through a pinhole into a dark enclosure. In the process, the image becomes inverted. He also further developed the understanding of depth perception through binocular vision.

I chose ibn al-Haytham as the guiding spirit of this blog because of his exploration of shifting perception and perspective. Using mirrors and lenses, he revealed the multiple permutations of the ways human beings come to see their world. Sometimes one has to flip an image upside down in order to see it properly, or at least see it anew.

The twelfth-century Arab-Sicilian geographer al-Idrisi’s map of the world (hint: flip it over)

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