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Why are the first three of Aquinas’s Five Ways considered cosmological arguments?
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Thomism
St. Thomas Aquinas Enthroned Between the Doctors of the Old and New Testaments, with Personifications of the Virtues, Sciences, and Liberal Arts, fresco by Andrea da Firenze, c. 1365; in the Spanish Chapel of the Church of Santa Maria Novella, Florence.
The first three of St. Thomas Aquinas’s Five Ways—the arguments from motion, causation, and contingency—are classified as cosmological arguments because they derive the existence of God from observable features of the natural world and the universe’s existence.1
These arguments function through a specific logical progression:
- Starting Point: Each begins with a general truth about natural phenomena, such as the existence of change, the necessity of efficient causes, or the contingent nature of beings.1
- The Chain of Dependency: Aquinas observes that these phenomena cannot form an infinite regress. For instance, motion requires a prime mover, and efficient causes require a first cause to avoid an endless chain of dependency.12
- Ultimate Ground: By identifying the impossibility of an infinite series, the arguments conclude that there must be an ultimate, unconditioned ground of reality that is not itself caused or moved by anything else.312
In Thomism, these demonstrations serve as natural theology, using reason to discern divine truth within the order of the cosmos.1