4.3.5 Late Medieval Philosophy in Christian Europe

Christian philosophy during this period is influenced by the development of two institutions: the university and the monastery. The development of these institutions influenced the form that philosophy would take during this period. It was in these institutions that a systematic effort was made to combine philosophy and theology in the Christian world. The attempt to reconcile challenges posed to theology by philosophy is illustrated in the voluminous work of Bonaventure (1221–1274) and Thomas Aquinas (1225–1274).

Bonaventure

Bonaventure, a Franciscan friar from Italy, traveled to the University of Paris in 1235, where he encountered Aristotle, the Islamic philosophers, and a rigorous course of logic. Bonaventure fused Augustinian ideas with Aristotle. In his illumination argument, he argued that God is the source of all knowledge but that “knowledge of the divine truth is impressed on every soul” (quoted in Houser 1999, 98). The acquisition of knowledge proceeds from effect, the outward world that we observe, to its cause, God. Knowledge is acquired through reasoning, using abstract ideas, propositions, and observed correlations, but certainty about this knowledge is only obtained through Augustine’s process of inner reflection or meditation through which we see the unchangeable divine light.

Thomas Aquinas

Thomas Aquinas (1225–1274) is the quintessential Scholastic philosopher, whose many works determined the course of European philosophy for generations. Somewhat like Immanuel Kant (1724–1804) several centuries later, philosophers after Aquinas knew that they would have to contend with his writings, either by extending his project or critiquing it. Aquinas saw that Scholastic philosophy needed to be reinvigorated, and he introduced the work of Jewish and Islamic philosophers to medieval Christian thought, bringing new ideas and approaches to philosophy (Van Norden 2017).

Aquinas is probably best known for his five ways to demonstrate the existence of God. The five ways are considered natural theology because Aquinas does not depend upon the authority of the church to justify the existence of God. Instead, he writes that we can define God in five ways: as an unmoved mover, first cause, necessary being, absolute being, and grand designer. In order to avoid an infinite regress, we must assume an unmoved mover who put all the entities into motion. Similarly, God is the first cause of everything that exists, or else we face an infinite causal regress. Everything that exists has contingent existence, save for God. God is the necessary being upon which every contingent being depends. Contingent beings have qualities that are relative to one another (bigger and smaller, etc.), which entails an absolute being to whom all these are relative. Finally, the evidence of design in the world implies a grand designer. All natural bodies act to achieve an end. For example, an acorn gives rise to a tree. However, not all natural bodies are aware of and able to direct themselves to achieve this end. Therefore, an intelligent being must exist to guide these natural beings toward their end.

We can see Aristotle’s influence in the metaphysics and epistemology of Aquinas as well as in his ethics and political philosophy. Aristotle defined God as the prime mover and “thought thinking itself.” We can discern the influence of this idea in Aquinas’s Five Ways. Aquinas also adopted Aristotle’s virtue ethics and adapted them to his Christian context.