St Thomas Aquinas Five Ways (Summa Theologica Question 2 Article 3)

Very often a Christian is asked the question “why are you a Christian? Why do you believe that God exists?”

Can the existence of God be proven logically and philosophically?

According to the Doctor of the Church, St Thomas Aquinas, there exist five ways to prove that God exists.

First Way

1. There exist changes in the world. And for every change(effect) there must be a cause.
2. It is impossible to believe that there is no first cause as every effect has a cause and if there is no first cause there will be no effects.
3. This first cause, we understand as God.

Second Way

1. Nothing is the cause of itself. Everything is caused by something as it is impossible for anything to create itself out of nothing.
2. There must be an uncaused first cause to start the chain going.
3. God is the uncaused first cause.

Third Way

1. There are things that exist and things that fail to exist,
2. If everything can fail to exist, there must be a time when everything doesn’t exist
3. But we exist, therefore if there had been a time when nothing exist then we shouldn’t be existing. (refer to second way)
4. There must be something that exist necessary for the existence of everything else.
5. This we understand as God

Fourth Way

1. For everything there are different degrees of quality. Like some people are smarter than others by a certain degree. Or that boiling water is hotter than tap water.
2. The things with the highest quality are the cause of the quality of the same kind. (such as fire which is hottest is the cause of everything else that is hot)
3. As Aristotle says that the greatest in truth are the greatest in being.
4. The greatest in truth, good and noble and of other perfections, this we understand as God.

Fifth Way

1. There are natural laws in the world. (gravity, a working ecosystem, even how the human body works without our active consciousness)
2. These things work towards a purpose and tend towards what is the best.
3. Consistency of the laws and purposeful actions reflect that things work with a purpose and not by mere chance.
4. Something that lacks consciousness can act in a unified way only if it is directed by something with consciousness and intelligence.
5. This intelligence we understand as God.