Muhammad ibn Zakariya al-Razi, known in the West as Rhazes, (854/865-925/935) was a Persian Muslim physician, alchemist and philosopher.

He was the early advocate of applying a rigorous evidence-based scientific approach to medicine.

A prominent polymath in medicine, philosophy, and chemistry, Razi wrote numerous books on medical and scientific subjects that have been influential in Western medicinal fields for centuries. He also wrote on logic, astronomy and grammar.

He is also considered the father of psychology, psychotherapy and paediatrics, and a pioneer of obstetrics and ophthalmology.

Born in the city of Ray, near present-day Tehran, he was an early proponent of experimental medicine. Razi became a successful doctor and served as chief physician of Baghdad and Ray hospitals.

He was famous for his compassion and devotion to the service of his patients, rich or poor.

As a teacher of medicine, he attracted students of all backgrounds and interests who participated in his classes from near and far.

Razi was the leading scholar of Islam and the Medieval Ages. He made fundamental and enduring contributions to various fields, which he recorded in more than 200 manuscripts.

He is remembered for numerous advances in medicine through his observations and discoveries.

Like many intellectuals in his day, he lived at various small courts under the patronage of minor rulers.

He was familiar with Greek medical knowledge and added substantially to it from his own observations. Razi viewed himself as the modern version of Socrates in philosophy and of Hippocrates in medicine.

He was among the first to use humoral theory to distinguish one contagious disease from another and wrote a pioneering book about smallpox and measles providing clinical characterization of the diseases. He also discovered numerous compounds and chemicals including alcohol and sulfuric acid among others.

His medical works were translated into various languages and became known among medieval European practitioners. His ideas deeply affected medical education in the West.

The most prominent of his books was the nine-volume encyclopedia “The Virtuous Life (al-Hawi)” which is known in Europe as “The Large Comprehensive” or “Continens Liber (Jameh-al-Kabir)”. The book contains considerations of various medical subjects and also criticisms of Greek and Aristotelian concepts.

It expresses many innovative views, and thus, many scholars consider Razi the greatest physician of the Middle Ages.

Some volumes of his other work “Kitab al-Mansuri”, namely ‘On Surgery’ and ‘A General Book on Therapy’, became part of the medical curriculum in Western universities.

“Al-Judari wal Hasabah” was the first treatise on smallpox and chicken pox, and is largely based on Razi’s original contribution: It was translated into various European languages. Through this treatise, he became the first to draw clear comparisons between smallpox and chicken pox.

In addition to being a physician, he compounded medicines and later gave himself over to experimental and theoretical sciences. He has portrayed several chemical reactions in great detail and also given full descriptions of about 20 instruments used in chemical investigations.

“Kitab-al-Asrar” is one of such books that deals with the preparation of chemical materials and their utilization.

Razi introduced many practical, progressive, medical and psychological ideas. His philosophical writings were neglected for centuries but in the 20th century they were reviewed by many scholars who appreciated their importance.

About 40 of his manuscripts are still kept in the museums and libraries of Iran, France, the UK and India. His contribution has greatly influenced the development of science and particularly medicine.

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