Who Was Ibn al-Haytham?
Full name (?): Abu Ali al-Hasan Ibn al-Haytham al-Basri (965-1040), known in the European Middle Ages as Alhazen.
He was a scholar of mathematics, physics, mechanics, astronomy, philosophy, and medicine. He’s associated with the “Muslim scholars’ trio” of the 10th - 11th centuries. The other two were al-Biruni (973 - 1048) and Ibn Sina (980 - 1037).1
From Ibn al-Haytham’s tract “Doubts on Ptolomey”:
Truth is sought for its own sake … It is not the person who studies the books of his predecessors and gives a free rein to his natural disposition to regard them favourably, who is the seeker after truth. But rather the person who is thinking about them [and] is filled with doubts … who follows proof and demonstration rather than the assertion of a man whose natural disposition is characterised by all kinds of defects and shortcoming…. A person who studies scientific books with a view to knowing the truth, ought to turn himself into a hostile critic of everything he studies … if he takes this course, the truth will be revealed to him and the flaws … in the writings of his predecessors will stand out clearly.2
The Book of Optics
His Book of Optics (Kitab al-Manazir) was translated anonymously in the 12th/13th centuries. It’s about the experimental and mathematical study of the properties of light.
The main feature of Ibn al-Haytham’s method is the use of experiments to test hypothesis. A theory is a modeling of observed facts. An experiment is designed to test the hypothesis on which the (mathematical(?)) theory is based.3
Western textbooks teach that Galileo Galilee (1564 - 1642) is the father of the scientific method. Robert Grosseteste (d.1253) and Roger Bacon were the European predecessors of Galilee.4
Ibn al-Haytham’s Book of Optics was a source for Bacon’s Opus Majus.