November 28, 2012


It’s difficult to imagine anything that better emblematises the conflict between science and religion than the image of an unrepentant Galileo, scowling as he is forced by the Church to recite his abjuration of heliocentrism. Galileo’s conflict with the Church was so dramatic that it’s tempting to view interactions between science and religion as zero-sum, where science gains ground to the extent that religion loses territory.

Before the Enlightenment, however, direct conflicts where people tried to use science to supplant religion were extremely rare; most conflicts were about the correct way to integrate religion and science.


The 8th century marked the beginning of the “Islamic Golden Age”, where the Islamic world rapidly translated and assimilated the philosophical and astronomical texts of other cultures. The translated Aristotelian corpus, combined with a pragmatic religious motivation1, helped Islamic astronomy progress rapidly during this era.

The influence of the Aristotelian corpus was not limited to astronomy, however. Aristotelian physics deeply influenced Islamic philosophical cosmology, particularly the Peripatetic School, of which Ibn Sina (Latinised as Avicenna) was the most influential . Ibn Sina was enthralled with the Aristotelian framework, and his cosmogony was a distinct synthesis of Islamic and Aristotelian thought, positioning the universe as the necessary and eternal product of God. This was a radical departure from the creation ex nihilo advocated by classical Muslim theologians, and al-Ghazali, an influential 11th-century Islamic theologian, argued forcefully against these claims in The Incoherence of the Philosophers.

al-Ghazali’s issues with Peripatetic doctrine were deeper than mere cosmogony, however. al-Ghazali advocated occasionalism, a manifestly anti-Aristotelian theory of causation that places God as the direct cause of all events. For occasionalists, the existence of secondary causation would entail that “the hand of Allah is chained”2, contrary to His omnipotence.

Despite his deep disagreement with the physics of Aristotle, al-Gazali recognized that certain elements of astronomy were undeniable, and even important to Islam. al-Gazali worried that a wholesale repudiation of the entirety of Hellenistic thought could drive students away from Islam, and argued that it was possible to engage in the mathematical and observational practice of astronomy without importing the metaphysical baggage of Aristotelian thought. Thus, al-Gazali offered an “instrumentalist” view, allowing the utility of astronomy without committing to the reality of the entities posited by Aristotelianism, a path that would later be significant for Galileo.

The dispute between al-Gazali and Ibn Sina was considerably more nuanced than a simple head-on clash between Aristotelianism and Islam. Rather, their divide broke along the lines of what each considered non-negotiable to their religion; while Ibn Sina is happy to jettison occasionalism and creation ex nihilo in his quest for a harmonized Islamic Aristotelianism, al-Gazali views these ideas as sacrosanct, and rejects that they may be discarded.


By 1245, a distinctly Aristotelian natural philosophy formed the basis of the arts curriculum in the University of Paris, the most important intellectual center of medieval Europe . This embrace of Aristotle’s thought caused great tension between the theology and arts faculties at the university. The theologians echoed al-Ghazali’s sentiments that Aristotle’s ideas (such as the idea that rectilinear motion of celestial bodies was impossible, as it would result in a vacuum) implied that there were limits to God’s supposed omnipotence.

In 1277, the Bishop of Paris issued a lengthy list of ideas to be condemned, including the idea that “God could not move the heavens with rectilinear motion”, and the eternity of the cosmos. Interestingly, it also included entries that point to its genesis in the interfaculty conflict:

    1. That one does not know anything more by the fact that he knows theology.
    1. That the teachings of the theologian are based on fables.

In this sense, the condemnation appears to be a far less measured response to Aristotelianism than the one articulated by al-Ghazali. While al-Ghazali was able to offer a sort of compromise between embracing and rejecting Aristotle, the Bishop of Paris merely linked the teaching of Aristotelian philosophy with the anti-theological attitudes expressed in condemnations 180-183, and licensed excommunication of anyone teaching the listed errors.

The list of condemned errors included theses from St. Thomas Aquinas who had developed a natural theology that drew heavily on Aristotle. Although the condemnation delayed the role of Thomism in Catholic doctrine, by 1567 Aquinas was formally recognised as a doctor of the church, and his pervasive influence would play a key role in the confrontation between Galileo and the Church.


By the late sixteenth century, Aquinas’ influence was so great that the 1599 Ratio Studiorum, which laid out global standards of Jesuit education, required the dismissal of any professor who was hostile to Thomism. Aristotelian astronomy was firmly entrenched in Church teaching, and centuries of work by theologians had built a scaffolding of Biblical support for geocentrism.

It was into this environment that Galileo set out to make a fresh case for Copernican heliocentrism, which had languished in relative obscurity since its initial publication in 1543. With his telescope, Galileo had discovered novel evidence for heliocentrism, including the phases of Venus. Galileo was aware, however, that Copernicus’s defence of heliocentrism, De revolutionibus orbium coelestium, had been condemned by the Congregation of the Index in 1616, for presenting heliocentrism as true, rather than as a mere mathematical tool, which would have been acceptable. This ruling mirrored the instrumentalist path laid out by al-Ghazali, where astronomy was permissible as long as the entities posited by such theories were not taken to be real.

It was difficult for Galileo to pursue this path, however. He had observed physical evidence of heliocentrism; arguing for an instrumentalist astronomy by appealing to the phases of Venus would be transparently disingenuous. Instead, Galileo attempted to use a dialogue format to argue for heliocentrism, but proved insufficient to prevent Galileo from being tried and sentenced on suspicion of heresy in 1633.

Galileo refused to take the instrumentalist option because he was convinced of the reality of heliocentrism. In his Letter to the Grand Duchess Christina, he argued for a new way to harmonise Church teaching and astronomy, arguing that Nature and Scripture were “two books” of God, and that these could never conflict. If Nature demonstrated that geocentrism was false, the scriptural evidence3 that ostensibly supports geocentrism should be interpreted figuratively. By arguing this position, Galileo was contradicting the Counter-Reformation principle that only bishops or councils of the Church had the authority to interpret scripture.


Galileo’s condemnation by the Church, while easily viewed as a straightforward case of science conflicting with religion, is more informatively characterised as a disagreement over ways in which religion and science could be reconciled. Galileo’s conception of the “two books” was one such path rejected by the Church.

Another path was given by al-Ghazali, who offered instrumentalism al-Ghazali was motivated by what he saw as non-negotiable aspects of his religion.

The 1277 Condemnation perhaps fits the template of “integration instead of opposition” poorly, but the validity of religion was never called into question by either side, with debates revolving around what is considered non-negotiable in religion rather than an outright rejection of religion itself. These three cases all demonstrate that the interaction between natural philosophy and religion was considerably more nuanced than simple diametric opposition.

  1. Astronomy proved useful in the practice of Islam, including the timing of Ramadan, the prayer times, facing Mecca, etc.

  2. The Qur’an attributes this phrase to the Jews before repudiating and condemning this notion.

  3. Including passages where “the sun stood still” at God’s command.