Al-Ghazali's Incoherence of the Philosophers (1095)

The Incoherence of the Philosophers (Arabic: Tahafut al-falasifa) is a book by the Persian theologian Abu Hamid al-Ghazali, completed in early 1095 in Baghdad. In it al-Ghazali attacked the Greek-inspired philosophy of Avicenna and al-Farabi, arguing that their proofs failed and that some of their teachings amounted to unbelief. It became one of the most influential works of medieval Islamic thought and provoked a famous reply from Averroes.

Background: al-Ghazali and the falasifa

Al-Ghazali was born around 1058 at Tus in Khorasan, in north-eastern Iran. He studied law and theology at Nishapur under the renowned scholar al-Juwayni. In 1091 the Seljuk vizier Nizam al-Mulk appointed him to teach at the Nizamiyya madrasa in Baghdad, then the most prestigious college in the Sunni world.

The falasifa (from the Greek philosophia) were Muslim thinkers who built on Aristotle and the Neoplatonists. The greatest of them, Avicenna (Ibn Sina, died 1037), had created a sweeping system covering logic, physics, the soul and God. Many of its claims, such as an eternal universe flowing necessarily from God, sat uneasily with the Quran.

Al-Ghazali decided to study philosophy thoroughly before refuting it. He first wrote The Aims of the Philosophers (Maqasid al-falasifa), a clear, neutral summary of their views, and then the Incoherence itself.

The argument of the Incoherence

The book is organised into twenty discussions. In each, al-Ghazali sets out a philosophical thesis and tries to show that the philosophers had not demonstrated it with the strict logic they themselves demanded. His aim was not to replace their system with another, but to show that reason alone could not settle these questions.

Three positions he judged to be outright unbelief (kufr):

• that the world has existed from eternity and was not created in time;
• that God knows only universals and not individual things and events;
• that the soul survives death but bodies are not resurrected.

The other seventeen theses he classed as errors or innovations, serious but not placing their holders outside Islam. His verdict had legal weight, since al-Ghazali was a respected jurist of the Shafi’i school.

Causation and occasionalism

The most famous section is the seventeenth discussion, on cause and effect. Al-Ghazali argued that we never observe a necessary link between a cause and its effect, only that one regularly follows the other. When fire touches cotton, the cotton burns, but nothing in the observation proves that the fire itself must produce the burning.

For al-Ghazali, God creates each event directly, normally in a regular order that makes the world predictable. This view, usually called occasionalism, left room for miracles. Philosophers have often compared his analysis to David Hume’s sceptical treatment of causation some 650 years later, although the two thinkers drew very different conclusions.

Crisis and conversion

In 1095, the same year he completed the Incoherence, al-Ghazali suffered a personal crisis. By his own account he became doubtful of his motives, lost his appetite and found himself unable to speak in the lecture hall. In November 1095 he left Baghdad, ostensibly on pilgrimage.

He spent around a decade travelling to Damascus, Jerusalem, Hebron, Mecca and Medina, living as a Sufi, a follower of Islamic mysticism. During this period he wrote his masterpiece, The Revival of the Religious Sciences (Ihya ulum al-din). In 1106 he returned to teaching at Nishapur, and later wrote the autobiography Deliverance from Error (al-Munqidh min al-dalal). He died at Tus in December 1111.

Reception and legacy

Al-Ghazali’s prestige earned him the honorific Hujjat al-Islam, “Proof of Islam”. His critique helped redirect Sunni theology: later theologians such as Fakhr al-Din al-Razi absorbed philosophical methods and logic into their own work, rather than abandoning them.

In al-Andalus, Averroes (Ibn Rushd) answered him around 1180 in The Incoherence of the Incoherence (Tahafut al-tahafut), defending Aristotle line by line. In Latin Europe, the Aims of the Philosophers was translated in the twelfth century, so that scholastics knew “Algazel” mainly as a summariser of philosophy. Some even assumed he shared the views he had described.

Myths and facts

A common claim is that al-Ghazali single-handedly ended science and philosophy in the Islamic world. Historians largely reject this. In Deliverance from Error he explicitly accepted mathematics and logic as sound, and he warned that rejecting proven astronomy would only damage religion. Astronomy, medicine and philosophy continued for centuries after him, notably at the Maragha observatory in the thirteenth century.

Timeline

• c. 1058: Al-Ghazali born at Tus in Khorasan.
• 1091: Appointed professor at the Nizamiyya madrasa in Baghdad.
• 1094–1095: Writes The Aims of the Philosophers, then completes The Incoherence of the Philosophers in early 1095.
• 1095, November: Leaves Baghdad after a spiritual and physical crisis.
• 1095–1106: Travels and lives as a Sufi; writes The Revival of the Religious Sciences.
• 1106: Returns to teaching at Nishapur.
• 1111, December: Dies at Tus.
• c. 1180: Averroes writes The Incoherence of the Incoherence in reply.

Why it matters

The Incoherence of the Philosophers is a high point of the medieval debate between faith and reason. Its arguments on causation still interest philosophers today, and its clash with Averroes remains one of the best-known intellectual exchanges of the Middle Ages.