Ibn al-Haytham was an Arab mathematician, physicist, and astronomer of the Islamic Golden Age. He is best remembered for his contributions to the principles of optics for which he is called the father of modern optics. He was the first person to explain visual perception. A polymath, Ibn al-Haytham also wrote influential books on philosophy, medicine, and theology.
Ahmad ibn Hanbal was an Arab Muslim theologian, jurist, hadith traditionist, and ascetic. He is credited with founding one of the four prominent legal schools of Sunni Islam, the Hanbali school of Sunni jurisprudence. A highly active and influential scholar, Ahmad ibn Hanbal is widely regarded as one of the most respected intellectual personalities in the history of Islam.