Thomas Aquinas offered five arguments for God's existence
Saint Thomas Aquinas lays out five proofs for the existence of God. They are simple, but also difficult to refute reasonably. In summary, he argues:
- There must be a First Mover. We know that everything that is in motion is caused by a mover. Nothing in the world moves itself, therefore the first mover must be outside the world.
- There must be a First Cause. Similarly, we see that many things are the result of cause and effect. There must be a first efficient cause, and that is God.
- Necessary Being. Everything that exists relies on another for its existence (e.g. babies exist because of their parents, back until the very first man and woman). There must be, necessarily, a Being from whom all existence comes, who does not rely on any other being for his existence.
- Perfect Being. Just as clearly as we can know that one thing is greater than something else or truer than something else, we are able to know that these things are short of perfection. Perfection must exist and that perfection is God.
- The Designer. The world is proof of an intricate and complex design. This design is not haphazard, but rather the sign of a Creator.
The First Vatican Council insists that not only are faith and reason compatible, but that they actually support one another. It is true that who God is in himself is beyond our natural capacity to know. This is logical because we are created by God, and are therefore not equal to Him and cannot know him fully by our own powers. Vatican I says that God is “completely simple and unchangeable spiritual substance” – his nature makes God different from any created thing. Faith is a gift from God, however, which allows us to know him in himself.
However, knowing who God is is different than knowing that he exists. We are able to know that he exists from the structure of the created world not merely by looking at scientific evidence, but also by using our natural capacity for reason to look at the scientific world and what it points to – a first mover, a supreme being, a first cause.
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