Reason, because it teaches us to discover, question, and innovate, was the enemy; al-Ghazali argued that in assuming necessity in nature, philosophy was incompatible with Islamic teaching, which recognizes that nature is entirely subject to God’s will: “Nothing in nature,” he wrote, “can act spontaneously and apart from God.” While al-Ghazali did defend logic, he did so only to the extent that it could be used to ask theological questions and wielded as a tool to undermine philosophy. Sunnis embraced al-Ghazali as the winner of the debate with the Hellenistic rationalists, and opposition to philosophy gradually ossified, even to the extent that independent inquiry became a tainted enterprise, sometimes to the point of criminality. It is an exaggeration to say, as Steven Weinberg
claimed in the Times of London, that after al-Ghazali “there was no more science worth mentioning in Islamic countries”; in some places, especially Central Asia, Arabic work in science continued for some time, and philosophy was still studied somewhat under Shi’ite rule. (In the Sunni world, philosophy turned into mysticism.) But the fact is, Arab contributions to science became increasingly sporadic as the anti-rationalism sank in.