The “knife-edge theory” says that what saved science in Christianity and prevented its decline was the lifting of the Paris condemnations from 1277. The assumption is that, had the condemnations continued, science would have declined, similarly as it happened in Islam.

This hypothesis gives too much weight to a local event in a particular part of Europe. First of all, the condemnations were limited to Paris—in London, for example, they were never implemented.

Second, while in Islam there seemed to be a universal condemnation of Aristotelian  philosophers among the ulema and the theologians, in Europe many theologians had a positive attitude towards Aristotelian philosophy.

Western Europe in the Middle Ages was also deeply religious. Similarly to the Islamic view, God is seen as omnipotent in the Christian religion, too. The Judeo-Christian God of the Old Testament can create miracles and can even influence decisions of people directly. For example, in Exodus 9:12 of the Old Testament God “hardens the Pharaoh’s heart” so that he doesn’t listen to Moses. But such events are described in the Bible as individual interventions in the natural flow of things, i.e. as “miracles”. Compare this to Surah 14:4 which expresses a general readiness of God to intervene at any time.

In the New Testament—the main holy book of Christianity—Jesus/God is depicted as much more dependable than the God of Islam. Jesus promises Heaven for everybody who believes in him and accepts him as the savior; there is not much sign of the arbitrariness as expressed in Surah 2:284. Apart from the miracles performed by Jesus, there is little evidence in the New Testament of God wanting to arbitrarily meddle in nature or in human affairs. The New Testament also emphasizes free will. For example, Revelation 3:20 of the Bible says:’

Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.

“Opening the door”—accepting Jesus as the savior—is left to the person’s own decision.

Christian scripture allowed for Christian thinkers like William of Conches and Thomas Aquinas to develop ideas of a benevolent, loving God who does not arbitrarily interfere in the world. He created the world, for sure, but he also created dependable natural laws according to which the world functions. Thus, there are two types of causes: a primary cause, which is God, and secondary causes—the causes that we can see in nature, resulting from the laws of nature. As James Hannam writes in his book God’s philosophers:

[For] William of Conches … ‘natural laws’ are the secondary causes that God usually uses … by investigating natural causes, the philosopher does not threaten God’s omnipotence in any way. There is nothing to to prevent God from intervening directly and causing a miracle. However, we can only recognise a miracle as contrary to the normal course of nature if we already have some idea of what the normal course might be (Hannam, 2010, p. 64).

Thus, the Christian view of God allowed for the existence of stable natural laws, and so, in spite of many individual differences, there was no fundamental contradiction between Christian and Aristotelian views of the world.

For a Christian religious fundamentalist it was more difficult to find places in the New Testament supporting a view of God as constantly meddling in world affairs and denying freedom of choice to humans than it was for Muslim theologians finding the same in Islamic scriptures. Thus, it was easier for people like Thomas Aquinas, who tried to bring together the Christian religion and Aristotelian philosophy, to triumph against the clerical opposition. Aquinas showed in his work Summa theologica that Aristotle and the Christian religion could be reconciled.

The above doesn’t mean that the Islamic domain was necessarily doomed to experience the decline of scientific inquiry that then happened. History is not deterministic in this sense. Thus, if, instead of al-Ghazali some powerful falasifa or Mu’tazilite intellectuals in the 11th century had cherry-picked parts of the Quran which seemed to suggest a self-limiting, freedom allowing God, and had disregarded or played down verses like those mentioned above, maybe philosophy and science would indeed have continued to progress in the Muslim world.

Similarly, in the Christian world, a suppression of philosophical inquiry might have been possible, maybe through a more thorough enforcement of the 1277 Paris condemnations.

However, the point is that it was quite easy to find evidence for a constantly meddling, arbitrary God in the Quran (and in the Hadiths). Thus, arguably, such a picture of God emerging from the Islamic holy scriptures is more plausible for a Muslim believer than the self-limiting, freedom-allowing picture of the God of the Mu’tazilites. In contrast, it was quite easy to find evidence in the New Testament for a God who grants freedom of choice to humans and less easy to find evidence for constant meddling. Thus such a picture of God emerging from the New Testament is more plausible for a Christian believer than a constantly meddling, arbitrarily acting God.

Consequently, in the battle for the Muslim mind between falasifa on the one side, the traditionalists and the Asharites on the other side (with the Mu’tazilites  in the middle), the traditionalists and the Asharites were expected to win.

Similarly, in the battle for the Christian mind between theologian-philosophers like William of Conches and Thomas Aquinas—who wanted to integrate Greek philosophy and religion—on the one side and the Christian establishment (represented by the bishop of Paris) on the other, the theologian-philosophers were expected to win.

Not surprisingly, the outcome of these two battles was exactly as expected.