Science is a fundamentally secular endeavor: it tries to understand and explain the world on its own terms without invoking an almighty God.

In this sense, neither Western European Christianity nor Islam were initially a hospitable cultural environment for science to develop. In both cultures the mindset was profoundly religious. Both Christianity and Islam are monotheistic religions, with an omnipotent God at the center. An emphasis on this divine omnipotence in a culture discourages scientific inquiry, This is because an omnipotent God almost by definition is able to interfere in the world any time—if he so chooses. On the other hand, the principal goal of science is to understand the world and a large part of this understanding involves understanding causal relationships between events in the world. The more the idea of an omnipotent God is emphasized, the less sense it makes to investigate causal relationships in the world without constant reference to God.

In both cultures, however, external ideas also began to shape the mindset, in the form of the works of classical Greek authors, translated in large scale translation movements both in Islam and in the Christian West. These Greek authors emphasized regularity, predictability and natural causes in the Universe.

The Greek philosophers Plato and Aristotle were particularly important. In Western Europe, dialogues of Plato had been available in Latin translations before the 12th century. The dialogue Timaeus is especially relevant in the current context. In it Plato depicts the universe as a rational system created by a super-god (Demiurge) who, after having created the world, more or less withdraws from his creation and leaves it to its own devices, without much further interference. To be sure, the heavenly objects—the planets, the stars—are still under the control of gods. However,

unlike the gods of traditional Greek religion, Plato’s deities never interrupt the course of nature. Quite the contrary, it is the very steadfastness of the gods that, in Plato’s view, guarantees the regularity of nature (Lindberg, 2007, p. 42).

In Islamic domains, Plato’s dialogues were apparently mostly neglected during the translation movement and none of them were completely translated (Huff, 2017, p. 98).

However, many works of Aristotle were translated from Greek into Arabic during the great Greek-to-Arabic translation movement. Western Europe benefited from this in the 12th century when Aristotle’s works also started to become much more available in Latin translations, often from Arabic language copies, found in Spanish libraries during the reconquista (Christian forces re-conquering Spain from Muslims).

Aristotle did assume some divine influence in the world. His universe is similar to Plato’s. For example, each of the heavenly spheres has its own “Unmoved (or Prime) Mover”, a divine being who controls the movements of heavenly bodies—the planets, the Moon, the Sun, the stars—in those spheres. But the influence of these “Movers” was totally predictable, causing lawful behavior in their respective spheres. As David Lindberg writes in his book The Beginnings of Western Science,

… the Prime Mover is the object of desire for the celestial spheres which endeavor to imitate its changeless perfection by assuming eternal, uniform circular motions. (Lindberg, 2007, p. 60)

In contrast to the “changeless perfection” of the heavenly regions, Aristotle sees constant change on the Earth. Some of this change is caused by the heavenly “unmoved Movers” but — importantly for the future of science — Aristotle assumed that objects on the Earth can cause changes in themselves or in each other, without divine interference. One reason for that was that each object has its own nature which determines how it behaves. Furthermore, each object has a tendency to move to its natural place. For example, for a stone dropped the natural place is the surface of the earth.

Change, according to Aristotle, always involves four types of causes: a final cause, which is the purpose of the change and three other causes: formal, material, and efficient. The final cause is often identical to the formal cause.

In the above example, the efficient cause, or the “agent” of the change, is the person who releases the stone from his hand. The formal cause could be the same as the final cause, for example, the person wishes to break the stone by dropping it. The material cause is the tendency of the stone to move to its natural place, the surface of the earth. Note that in this example, all four causes are natural causes.

Both Plato’s and Aristotle’s ideas about the world were diametrically opposed to a conception of the universe in which an omnipotent God is the only cause for anything to happen—a God who not only has the power to interfere at any time, but does actually interfere in every moment. In a world like that there is any semblance of regularity only because God, for the moment, allows such regularity to exist.

In both Islam and in Western European Christianity their respective translation movements made the works of these Greek philosophers available. The ideas in these works provided a seed from which science and natural philosophy could potentially develop. Often against the resistance of religious scholars and authorities, in both of these cultures a number of theologians and philosophers made an attempt to make the new Greek ideas acceptable for society and even to  integrate these ideas into the existing religious framework. The next chapter will show how they succeeded in Islam and in Western Christianity.