Proof of God’s Existence: 5 Rational Demonstrations
Proof of God’s Existence
The Problem of Demonstration
We might think that God can be directly perceptible by reason, the way we see truths like “triangles have three sides.” Saint Thomas calls these propositions self-evident. In them, the predicate is included in the subject because the essence of its objects is the property referred to in the proposition. They are also evident to us when we see them as real with just understanding the concept subject.
If the existence of God is included in its essence, then we could grasp the truth of the proposition “God exists” with the mere understanding of the term “God.” Saint Thomas maintains that there can be no argument of this kind because the essence of God is not given to us as clearly as, for example, the essence of the triangle. This means that the proposition “God exists” is not obvious to us, even if self-evident (it is true that existence is included in the essence of God).
The Five Ways
According to Saint Thomas, the only rational demonstration of God’s existence is not adequate because it is not according to the human faculties. We must come from God as known to us, of sensible experience. His evidence (the Five Ways) have antecedents in Plato and Aristotle and are demonstrations a posteriori of the effects of the action of God in the world to go back to him as the ultimate cause.
1st Way: From Motion
Everything that moves is moved by something else and so on, but an infinite series of engines is not possible. Therefore, there is a need for a prime mover—an unmoved mover—to begin the series of movements.
2nd Way: By Efficient Causality
In the sensible world, there are efficient causes, which in turn have been caused because nothing can cause itself. There must be a first cause—an uncaused cause—because otherwise there would be no second causes nor, therefore, anything would exist.
3rd Way: By Contingency
Contingent beings are generated and decay. They exist but they could not have existed. If all beings were contingent, there would have been a time when nothing existed. Therefore, not all beings are contingent: it requires that in nature there is a necessary being. But every necessary being is the cause of another cause and need not be as an infinite series of necessary beings who have their need for other reasons. We must admit a necessary being per se.
4th Way: By Degrees of Perfection
We verify by degrees of perfection in things that there are some perfections such as goodness or truth. The greater or lesser degree of perfection of different things is determined by the extent to which they approach the highest degree of perfection. Therefore, there must be something that is so true and so good and therefore being par excellence because what is true is also good par excellence, being the maximum degree of excellence. And being is a cause of the goodness, truth, and perfection of all beings, and this cause is identified with God.
5th Way: By Intelligent Design
There is an order or purpose in the universe. Beings which do not have intelligence tend to an end not by chance but in a deliberate manner. Therefore, there must be an intelligent being, a supreme intelligence, to direct us.