Al-Razi (Rhazes)

Abu Bakr Muhammad ibn Zakariyya al-Razi, known in medieval Europe as Rhazes, was born in 854 CE in Ray, a city near present-day Tehran in Persia. He is one of the greatest physicians in the history of medicine — a rigorous clinician, a prolific author, and a bold thinker who placed careful observation of individual patients at the center of medical practice centuries before this became standard. Al-Razi came to medicine relatively late, reportedly after witnessing suffering in a Baghdad hospital during his thirties, and studied under Ali ibn Sahl Rabban al-Tabari. His talent was swiftly recognized, and he rose to lead the hospital at Ray and subsequently the great hospital of Baghdad, the capital of the Abbasid Caliphate. A famous story recounts that when tasked with choosing the site for a new Baghdad hospital, he hung pieces of fresh meat in different quarters of the city and selected the location where the meat rotted last, reasoning that the air there was purest — an early intuition of germ theory and environmental medicine. As a clinician he was unparalleled in his era. His most celebrated clinical achievement was the first clear differentiation between smallpox and measles, described in his treatise 'Fi al-Jadari wa al-Hasba' (On Smallpox and Measles). This work, translated into Latin and printed many times in Europe, described the symptoms, progression, complications, and treatment of each disease with an accuracy that would not be surpassed for centuries. He recognized that both were distinct diseases rather than variations of a single ailment and observed that recovery from smallpox conferred immunity — an insight that would eventually underpin the science of vaccination. His encyclopedic masterwork 'Kitab al-Hawi fi al-Tibb' (The Comprehensive Book on Medicine), known in Latin as the Continens, was a vast private notebook compiled over his lifetime and published posthumously. Running to dozens of volumes, it collected Greek, Syriac, Indian, and Arabic medical knowledge alongside his own clinical observations, making it one of the largest medical compilations in history. A second major work, 'Kitab al-Mansuri fi al-Tibb' (The Book of Medicine Dedicated to al-Mansur), was a systematic ten-volume medical textbook that became widely used in European universities in its Latin translation. Al-Razi also made lasting contributions to alchemy and chemistry, conducting systematic experiments on substances and classifying them into animal, vegetable, and mineral categories — a taxonomy that influenced later chemical understanding. He described laboratory procedures with unusual precision and improved distillation apparatus. In philosophy he was intellectually bold to the point of controversy, questioning the authority of religious tradition in matters open to rational inquiry — positions that brought him sharp criticism from theologians. In his later years his eyesight began to fail, reportedly from excessive study and the fumes of his laboratory work. When a physician offered to treat him, al-Razi reportedly declined, saying he had seen enough of the world. He died in Ray in 925 CE, nearly blind, leaving behind roughly two hundred works covering medicine, philosophy, alchemy, mathematics, and astronomy. His insistence that medicine must be grounded in observation of actual patients rather than merely in the inherited authority of the ancients marks him as a founder of clinical medicine in the fullest sense.