But the mullahs soon prohibited studying speculative thought (including philosophy) from non-Islamic sources. For example, the prominent Sufi scholar Abu Hamid al-Ghazali argued in his book The Incoherence of the Philosophers that Muslim philosophers who in any way called into question the teachings of the Qur’an or of Islam were infidels. This may sound similar to the Condemnations of 1277 except that al-Ghazali added that killing infidels was obligatory for all good Muslims. This kind of thinking put a real damper on philosophical development.
