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Ibn al-Haytham (Alhazen)
c. 965–c. 1040
Arab physicist and mathematician who worked in Basra and Cairo.
What they got right
He tested ideas about light by experiment and refused to accept even Ptolemy just because he was famous; truth-seekers should question the ancients, not trust them.
Skill it shows
Evidence and sources
Practise this skillAlso: Identifying assumptions
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 suspends his faith in them and questions what he gathers from them, the one who submits to argument and demonstration…
Worth knowing
He is often called 'the first scientist'; historians see that as an overstatement, though he was a genuine pioneer of experimental method. His Book of Optics showed vision comes from light entering the eye.
Try it yourself
Think of a respected source you rely on. Pick one of its claims and ask: what argument or demonstration actually supports it?