The Incoherence of the Philosophers

The Incoherence of the Philosophers (Tahāfut al-Falāsifa) is one of the most influential works of the Muslim thinker al-Ghazali (1056-1111). It was written around 1095, while he was professor of law at the Nizamiyya in Baghdad, one of the most prestigious colleges of its time. The college was partly meant to train scholars who could counter the religious propaganda of the Fatimid caliphs. The book is the second in a series of four works: the first, Maqāsid al-Falāsifa, gives a systematic account of Avicenna's philosophy; the third, Miyar al-ʿIlm, presents his logic; and the fourth, Al-Iqtisād fī al-iʿtiqād, sets out the Ashʿarite theology that the Incoherence aims to replace in matters of metaphysics.

The work mainly attacks Avicenna and al-Farabi, whom al-Ghazali accuses of following Greek philosophy even where, in his view, it contradicts Islam. Organized into twenty chapters, seventeen of them denounce positions he considers heretical, and three accuse the philosophers of unbelief. Those three concern the eternity of the world, the claim that God knows only universals and not particulars, and the denial of bodily resurrection. The book holds that, in metaphysics and in knowledge of the divine, faith must take precedence over philosophical reasoning. Al-Ghazali did not reject the sciences as a whole: he accepted logic, physics, astronomy and mathematics, and his dispute lay with metaphysics.

His most debated contribution is his critique of necessary causation. He argues that the connection between cause and effect is not necessary in itself but depends on God's decree. He illustrates this with the burning of cotton placed in contact with fire, which he attributes directly to divine will. This argument anticipates, by several centuries, the objections later raised by David Hume. The book also offers a theory of possible worlds, according to which the actual world is the best of all those God could have created.

Its influence was considerable. It helped establish the Ashʿarite school within Islamic thought and left a mark on mysticism and Sufism, as well as on Jewish religious thinkers such as Judah Halevi. The best-known reply came a century later from Averroes, in The Incoherence of the Incoherence (Tahāfut al-Tahāfut), which defends the philosophers and examines al-Ghazali's arguments one by one. Centuries later, the Ottoman scholar Khwajahzada also wrote a refutation of the work, while Ibn Tufayl and Ibn al-Nafis responded with philosophical novels.