Church authorities were uneasy about some of Aristotle's works and suggested censoring passages of his text that conflicted with Christian theology. They were also uneasy with Arabic commentaries of Aristotle, such as those presented by Averroes, because they made no attempt to adapt the philosopher's ideas to Christianity. Despite the skepticism of some medieval thinkers that Aristotle could be reconciled to Christianity, natural theology sought to embrace Aristotelian philosophy. Thomas Aquinas, the foremost natural theologian, endeavored to compose a synthesis of Christian and Aristotelian philosophy in the mid 13th century. Aquinas and John Duns Scotus, a Franciscan monk from the later part of the century, shared the belief that reason was sufficient to obtain at least a partial knowledge of God by studying creation (Hall, 2007). As natural theologians Aquinas and Duns Scotus participated in a project set out by Anselm in the 11th century of "faith seeking reason." In Medieval scholastic philosophy one finds an earnest and diligent endeavor to explore and later to test the limits of reason. Subtleties and semantics of the medieval conversation may seem antiquated to a modern audience. Still, this exploration did much to shape our understanding of logic, philosophy, and reason to the present day (Rubenstein, 2003).
Thomas Aquinas's work made use of Aristotelian syllogism as a scientific method (in the medieval sense) for obtaining knowledge. Syllogism is a form of deductive reasoning composed of a general statement, a second more precise statement, and a third necessary conclusion to be drawn from the proceeding statements. A syllogism takes the following oft cited form:
All men are mortal.
Aquinas sought to "scientifically demonstrate" the existence of God by reasoning through 5 ways. The 5 ways were built on observations regarding: motion, efficient causes of motion, the existence of entities, varying degrees of perfection, and the activity of unintelligent entities (Hall, 2007).
Socrates is a man.
Socrates is mortal.
The importance of Aquinas's work does not lie in building an argument that would be satisfying to modern scientific sensibilities. What matters is the approach Aquinas took and how the work of subsequent philosophers built on it or worked to refute his reasoning. Aquinas used a form of medieval argument known as scholasticism. The scholastic approach involves first stating the arguments against, then for, the side a person wishes to defend. It is not enough just to point out the strength of the arguments for a given opinion, but to also point out the weaknesses for the other side (Williams, 2007). Aquinas integrated this approach to the examination of Aristotelian ideas. Through the work of Aquinas and his successors, scholasticism became synomous with Aristotelian philosophy. It was through the scholastic philosophers that Aristotelian ideas became reincorporated in the western intellectual tradition.
In Aquinas's lifetime, he was just one voice trying to define how Aristotle's ideas should be approached. Conservative thinkers were hostile to Aristotle's work and wished to suppress it. More radical thinkers, such as members of the Faculty of Arts from the University of Paris, enthusiastically embraced Aristotle, and taught his ideas without critique or regard to their impact on theological ideas (Rubenstein, 2003). Aquinas sought to marry Aristotelian ideas to Christian theology. He started from a similar position to those stated by naturalism the century before, that God did not violate natural law. He accepted Aristotle's view that human knowledge is acquired through sensory experience. While he believed that some aspects of reality are not accessible to rational thought, overall, he exhibited considerable confidence in the ability of reason to describe natural events and even come to an understanding of God.
In his own time Aquinas was censured by the conservatives and ridiculed by the radicals. A few years after Aquinas's death, when the Bishop of Paris issued the Condemnation of 1277 against Paris's Faculty of Arts, some of Aquinas's own ideas were included in the 219 condemned propositions (Luscombe, 1997). However, Aquinas's ideas had an enduring quality. Much of the scholastic philosophy that came after Aquinas either attempted to refine his ideas or tried to refute them.
One of the philosophers who would attempt to refine Aquinas's work was John Duns Scotus. Scotus came to maturity after the Condemnation of 1277, and so encountered a more theologically conservative environment than Aquinas. This perhaps diminished his confidence in the capacity of experience to obtain scientific certainty. Scotus also felt that Aquinas had potentially limited God's role too much by claiming that God didn't interfere with the rules of nature. He argued that God could do, and might well do, anything short of behaving in a logically impossible way. Still, Scotus rejected Henry of Ghent's theory that only divine illumination could lead to certainty (Hall, 2007).
It may seem counterintuitive that the philosophy of science could be advanced by an argument that asserted God's omnipotence. But Duns Scotus's logic led him in a direction that did just that. As a result of his assertion, he came to the conclusion that the laws of nature were only probable, not certain (Rubenstein, 2003). Additionally, he introduced the idea of falsification in his theology by arguing that some ideas about God could not be proved, but that they also could not be falsified (Hall, 2007). Furthermore, Duns Scotus argued for ontological parsimony. This idea, often identified as Ockham's Razor, looked to create explanations that involved the least number of steps possible. Although the idea of parsimony is currently associated with William of Ockham, it surfaced in the writings of a number of medieval thinkers before Ockham's time (Thornburn, 1918). Whatever the specific origins, it is an idea that flourished in the Middle Ages.
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