Al-Razi (Rhazes)
Persian physician and alchemist who distinguished smallpox from measles and pioneered clinical observation.
Who or what
Abu Bakr Muhammad ibn Zakariya al-Razi (c. 854–925), known in the West as Rhazes, was a Persian polymath.
He was director of the Baghdad hospital and wrote over 200 works on medicine, alchemy, and philosophy.
Why it mattered
Al-Razi was the first to distinguish smallpox from measles as distinct diseases with different symptoms and courses.
He emphasized clinical observation over theoretical speculation — a proto-scientific approach to medicine.
Key works and moments
He chose the site for Baghdad's hospital by hanging pieces of meat in different districts and selecting where decomposition was slowest.
His "Comprehensive Book on Medicine" (al-Hawi) was a 23-volume medical encyclopedia based on case studies.
Further detail
He classified diseases by symptoms and progression, not by humoral theory alone.
In alchemy, he classified substances into mineral, vegetable, and animal, and described distillation and crystallization techniques.
Legacy
Al-Hawi was translated into Latin as "Continens" and became a foundational medical text in medieval Europe.
His emphasis on observation and experimentation influenced later physicians including Ibn Sina.
More in Islamic Golden Age
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