Thomas Aquinas & William of Ockham: Two Philosophical Approaches to God

Posted on Nov 25, 2024 in Philosophy and ethics

Thomas Aquinas

The Five Ways to Prove God’s Existence

There are two main types of arguments for God’s existence:

  1. Ontological: This argument derives God’s existence from the very idea of God. The concept of a perfect being implies existence, as lacking existence would be a contradiction.
  2. Cosmological: This is the approach favored by Aquinas, drawing upon sensory experience and induction, influenced by Aristotle. It identifies God as the ultimate cause of observed phenomena.

Aquinas’s Cosmological Arguments

  • Motion: Based on the Aristotelian concept of potentiality and actuality, this argument observes that things are in motion. Nothing can move itself; everything is moved by another. This chain of movers leads to a First Mover, or Pure Act, identified as God.
  • Causation: We observe that things are caused. Nothing can be the efficient cause of itself. Tracing back the chain of efficient causes leads to the ultimate cause, God.
  • Contingency: This argument questions whether everything is contingent or if something is necessary. If everything were contingent, there would have been a time when nothing existed. Since something exists now, there must be a necessary being, God.
  • Degrees of Perfection: This argument observes that things possess qualities in varying degrees. These degrees imply a supreme standard for each quality. The union of all supreme qualities is God.
  • Order: The order in the physical world implies an intelligent designer, God.

William of Ockham

Knowledge and Universals

Ockham argued that knowledge is only of individual, specific things, derived from experience. Concepts have no cognitive value; they are merely names for things. This leads to the problem of universals:

  1. Exaggerated Realism (Plato, Augustine): Concepts have an independent reality, superior to individual things.
  2. Moderate Realism (Aristotle): Concepts exist within things (universalia in re) but are not separate from them.
  3. Nominalism (Ockham): Concepts are merely names with mental existence, not reflecting reality. Ockham’s nominalism further divides into positions where concepts are not even entities or are merely mental constructs.

Limitations of Reason

Ockham believed we cannot reason from experience to ultimate causes like God. This is due to:

  1. The nature of universals: Reasoning relies on concepts, which are merely mental constructs.
  2. The contingency of reality: The world, both physical and moral, is contingent. Its characteristics are not necessary and could be otherwise. Therefore, we must rely on senses and faith, not reason.

Ockham’s emphasis on contingency reflects a historical shift. Scholasticism heavily relied on reason, but Ockham asserted God’s omnipotence transcends human reason, applying to both the physical and moral realms. This challenged the natural law theory of Aquinas.