Al-Razi (Rhazes)

By Emre Yıldırım

He was the greatest clinician of the medieval world — and its most dangerous freethinker. Abu Bakr Muhammad ibn Zakariya al-Razi, known in Latin as Rhazes, ran the great hospital of Baghdad, wrote more than two hundred books, and distinguished smallpox from measles for the first time in history. He also wrote treatises arguing that reason outranks revelation, which made him, in the eyes of the orthodox, something close to a heretic. The hospital and the heresy were the same man.

Al-Razi came to medicine late. Born in Rayy, near modern Tehran, in 854, he was a jeweler, a musician, and an alchemist before turning to medicine around thirty — reportedly after a botched eye treatment made him determined to understand the art himself. He studied in Baghdad, rose to direct the Muqtadari hospital, and chose its site, the story goes, by hanging meat in different quarters of the city and picking the spot where it decayed slowest. Whether or not the tale is true, it captures his method: test, observe, decide.

His clinical masterpiece, On Smallpox and Measles, is the first clear differentiation of the two diseases — their rashes, their courses, their prognoses — and remained authoritative in Europe into the nineteenth century. His enormous al-Hawi, the Comprehensive Book of Medicine, is a twenty-three-volume encyclopedia of everything known to medicine, with his own clinical notes and doubts set alongside the authorities: he cites Galen constantly and corrects him constantly. He described the first known use of alcohol as an antiseptic, distinguished kinds of fever, wrote on diet, pediatrics, and surgery, and insisted that the physician's first duty is to the patient's own account of symptoms.

In chemistry — the field the Arabs called alchemy — al-Razi was the great systematizer. His Secret of Secrets classified substances into vegetable, animal, and mineral, described laboratory apparatus, and gave procedures for distillation, calcination, and crystallization that read like a modern lab manual. He was trying to make medicine, not gold.

And then there were the forbidden books: treatises on the eternity of the world, on the imposture of prophets, on the sufficiency of reason — works that survive only in quotations by the scandalized. Al-Razi argued that God gave all humans reason, and reason needs no prophets. For this, later biographers called him an atheist and a madman; the same biographers could not stop copying his medical books. He went blind late in life — from cataracts, or, one hostile story says, from a beating ordered by a patron angry at his failed alchemy — and died in Rayy in 925. The clinician the world trusted for eight centuries; the philosopher it tried to forget.

Impact on civilization

Al-Razi founded clinical differentiation — the discipline of telling diseases apart by careful observation — with his separation of smallpox and measles, and his Comprehensive Book organized all medical knowledge for the next eight centuries, in Arabic and in Latin translation. His chemical classifications and laboratory procedures moved alchemy toward chemistry; his antiseptic use of alcohol anticipated modern practice by a millennium. He proved that a physician's loyalty belongs to evidence, not authority — even the authority of Galen — the clinician who trusted his own eyes.