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Thinkers

Al-Razi

Islamic · Middle East · 865 to 925

Persian doctor and thinker who put reason above authority, and who wrote a famous medical encyclopedia.

What it is

Al-Razi was a Persian physician, philosopher and alchemist from the city of Rayy, who lived in the late ninth and early tenth centuries. He is counted among the greatest physicians of the Islamic world and also among its most controversial philosophers. Exact dates differ between accounts.

He wrote on medicine, philosophy and alchemy, among much else. His medical works were widely read, and his philosophy, which questioned religious authority, is known mostly through what other writers, often hostile, said about it.

The main ideas

  • Reason over authority. He criticised the great Greek physician Galen, and held that sound practice calls for independent thinking, not repeating the masters.
  • Five eternal principles. He is reported to have taught that the world arises from the interaction of God with four other eternal principles: soul, matter, time and place.
  • Matter made of atoms. He held an atomist theory of matter, in the manner of some early Greek thinkers.
  • Philosophy as a way of life. He saw himself as following Socrates in philosophy.
  • Care of the soul. He wrote a book of ethical advice, often called the Spiritual Medicine, offering a kind of treatment for the soul beside the treatment of the body.

What it looks like in practice

Picture a doctor in a hospital who is told that a respected old authority prescribes a certain treatment, and who has seen it fail in front of them. In the spirit of al-Razi, the doctor would trust the evidence over the name, and say plainly where the authority is wrong. This is an illustration of his stance, not a passage from his writing.

Books and moments

  • The Book for al-Mansur is a large medical work dedicated to the ruler of Rayy.
  • The Comprehensive Book is a huge collection of medical notes and excerpts, finished by his students after his death.
  • A treatise on smallpox and measles is celebrated for treating them as different illnesses.
  • Doubts about Galen gathers his criticisms of Galen.
  • Hospitals in two cities. He ran or led hospitals in Rayy and in Baghdad.

Questions and criticism

  • What did he believe about religion? Reports say he criticised religion and prophecy. His own writings on the subject are mostly lost, so we depend on hostile sources, and the question stays open.
  • Five principles. This doctrine is known only through reports by writers who were often opposed to him. It is fair to ask how he would have put it himself.
  • Doctor or philosopher? His fame rests mostly on medicine. It is fair to ask how far his philosophy and his medical practice shaped each other.

Close neighbours

The pages on Ibn Sina and Al-Farabi sit closest among thinkers of the same world and period. The page on Socrates shows the model he claimed, and Democritus shows the atomist idea in earlier form.

Written by epchē in our own words, and checked against independent sources on 29 October 2026. The sources are listed below.

Who they connect to

Influenced by

  • Plato · He took Plato as a main guide on the soul and on the aim of becoming like the divine by reason. (scholars disagree about this link)

Other Islamic thinkers

Sources we used

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