(or Rasis; Latin forms of Razi; full Arabic name, Abu Bakr Muhammad Ibn Zakariya al-Razi). Born 865 in Rey; died there 925 or 934. Iranian scholar, encyclopedist, physician, and philosopher; rationalist and freethinker.

Rhazes supervised clinics first in Rey and later in Baghdad. He was very familiar with the science, medicine, and philosophy of antiquity. He apparently wrote some 184 works in all, of which 61 have come down to us. These works dealt with philosophy, ethics, theology, logic, medicine, astronomy, physics, and chemistry (alchemy). His works were translated into Latin in Europe between the tenth and 13th centuries.

Rhazes’ scientific studies are characteristically free of dogmatism, utilize experimentation, and display a practical orientation. His philosophical thought, resembling certain kinds of gnosticism, is based on a doctrine of five eternal principles: creator, soul, matter, time, and space. Reason, sent by the creator, inspires the soul, which is imprisoned by matter, to strive for liberation; the path to liberation is the study of philosophy. The atomism of Rhazes is similar to that of Democritus. Rhazes believed in absolute space and absolute time, and he accepted the existence of a multiplicity of worlds. In ethics, he attacked asceticism and urged an active life in society, on the model of Socrates.

Rhazes sharply criticized all the religions that existed in his time. He wrote the antireligious treatise Mashariq al-anbiya (The Dawn of the Prophets), which evidently served as the basis for the medieval Latin lampoon entitled De tribus impostoribus. According to Rhazes, truth was one but religions were many; consequently, all religions were false, and one should read not Scripture, but the books of philosophers and scientists. His antireligious statements provoked fierce attacks by Muslim thinkers of the tenth and 11th centuries, particularly Farabi.

Rhazes’ principal medical works are al-Hawi (Continent of Medicine) and the ten-volume Book of Medicine Dedicated to Mansur. They are unique medical encyclopedias in Arabic; translated into Latin, they served as a guide to physicians for centuries. In On Smallpox and Measles (Russian translation in V. O. Gubert, Smallpox and Smallpox Vaccination, vol. 1, St. Petersburg, 1898), Rhazes gave a classic description of these diseases, noting immunity to repeated infection; he is known to have made use of vaccination (variolation).

Rhazes is believed to have introduced the practice of writing a medical history for each patient. He was the first to describe an instrument for removing foreign bodies from the pharynx and one of the first to use cotton wadding in bandaging and catgut in sewing up wounds. He drew up instructions for equipping hospitals and choosing hospital sites. Among his other works are One Physician Cannot Cure All Diseases, which takes up the importance of specialization among doctors, and Medicine for Those Who Have No Doctor, about medical aid and self-help for the poor.