Ibn al-Haytham (Latinized as Alhazen or Alhacen) was born in Basra in 965 A.D. [354 A.H.], but produced nearly all of his work in Cairo's al-Azhar Mosque, where he wrote nearly one hundred works on topics as diverse as poetry and politics. Al-Haytham is primarily known for his writings on geometrical optics, astronomy, and mathematics, and for nearly four hundred years his treatment of the geometry of reflection from flat and curved surfaces has been known as "Alhazen's problem." However, as discussed in this paper, with his landmark seven-volume Kitāb al-Manāzir [Book of Optics], published sometime between 1028 [418 A.H.] and 1038 [429 A.H.], al-Haytham made intellectual contributions that subsequently were incorporated throughout the core of post-Medieval Western culture. His seminal work on the human vision system initiated an unbroken chain of continuous development that connects 21st century optical scientists with the 11th century Ibn al-Haytham. The noted science historian, David Lindberg, wrote that "Alhazen was undoubtedly the most significant figure in the history of optics between antiquity and the seventeenth century." Impressive and accurate as that characterization is, it significantly understates the impact that al-Haytham had on areas as wide-ranging as the theology, literature, art, and science of Europe.