Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham ( 965–1040) was an Arab scientist, mathematician, astronomer, and philosopher. He made significant contributions to the principles of optics, astronomy, mathematics, meteorology, visual perception and the scientific method. Ibn al-Haytham is widely considered to be one of the first theoretical physicists, and an early proponent of the concept that a hypothesis must be proved by experiments based on confirmable procedures or mathematical evidence. In medieval Europe, Ibn al-Haytham was honored as Ptolemaeus Secundus. (The "Second Ptolemy.") He is featured on the obverse of the Iraqi 10,000 dinar banknote.
"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 ... 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." — Alhazen