Historical reliability of the Quran concerns the question of the historicity of the described or claimed events in the Quran. The Quran is viewed to be the scriptural foundation of Islam and is believed by Muslims to have been sent down by Allah (God) and revealed to Muhammad by the angel Jabreel (Gabriel). Muslims have not used historical criticism in the study of the Quran, but they have used textual criticism in a similar way used by Christians and Jews. It has been practiced primarily by secular, Western scholars such as John Wansbrough, Joseph Schacht, Patricia Crone, and Michael Cook, who set aside doctrines of the Quran's divinity, perfection, unchangeability, etc., accepted by Muslim scholars, and instead investigate the Quran's origin, text, composition, and history.