The Five Ways of St. Thomas Aquinas

St. Thomas Aquinas was a Christian philosopher in the 1200’s. He is known for his Summa Theologica and his Five Ways of proving God’s existence: The Unmoved Mover, The Argument of the First Cause, The Argument from Contingency, The Argument from Degree (or Perfection), and The Argument of Intelligent Design.

The Unmoved Mover

The Argument of the Unmoved Mover tries to explain that God must be the cause of motion in the universe. This argument is the first of St. Thomas Aquinas’ Five Ways. His Argument from Motion is based on the observation that any object had to have some other object or force to put it into motion.

An interpretation of his argument goes as follows:

1. Some things are in motion.
2. Whatever is in motion is put in motion by something else.
3. Whatever put that object in motion must itself be put in motion by something else.
4. Through a chain of events, each object moving another object must have been moved by yet another object further in the past.
5. There cannot be an endless chain of moving events going on to infinity.
6. Without a first mover, there would be no motion.
7. Therefore, it is necessary to arrive at a first mover; a first mover put in motion by no other.
8. This first mover is God.


The Argument of the First Cause

The Argument of the First Cause is the second of St. Thomas Aquinas’ Five Ways. The argument of the first cause tries to prove that God must have been the cause, or the creator of the universe. It is therefore a form of the cosmological argument. The argument states that no object is capable of creating its own self. Every created object had to be created by something or someone else. Going back in time, there had to be the first creator. This first creator could not itself, have been created. A similar philosophy is discussed by St. Augustine.

An interpretation of his argument goes as follows:

1. All things and beings that exist are caused by other things.
2. Nothing can be the cause of its own self. If so, it would exist prior to itself.
3. Through a chain of events, each object of being causing the existence of another object or being, must have been caused by yet another object or being.
4. There cannot be an endless chain of objects or beings causing the existence of other objects or beings.
5. Without a first cause, there would be no objects or beings in existence today.
6. Therefore, it is necessary to arrive at a first cause; a first cause which is caused by no other.
7. This first cause is God.

Another philosopher who spoke out on this subject was Avicenna. According to Avicenna, the universe consists of a chain of actual beings, each giving existence to the one below it and responsible for the existence of the rest of the chain below. Due to the fact that there cannot be an infinite past to our universe, the chain as a whole must terminate in a being that is wholly simple and one, whose essence is its very existence and therefore is self-sufficient and not in need of something else to give it existence. For an enlightening understanding on the impossibility of an infinite past, read the novel, Conversations with a Stranger.

The Argument from Contingency and Necessary Objects

The Argument from Contingency and Necessary Objects is the third of St. Thomas Aquinas’ Five Ways. There are only two kinds of objects in existence: contingent beings and necessary beings. A contingent being is an object or being that cannot exist without a necessary being causing its existence.

An interpretation of his argument goes as follows:

1. Many things in the universe may either exist or not exist. Such things are called contingent beings.
2. It is impossible for everything in the universe to be contingent, for then there would be a time when nothing existed, and so nothing would exist now, since there would be nothing to bring anything into existence, which is clearly false.
3. Therefore, there must be a necessary being whose existence is not contingent on any other being or beings.
4. This being is God.

Another way of stating the argument is as follows:

1. We find things (beings) are possible to be, and possible not to be.
2. That which is possible not to be, at some time is not.
3. If everything is possible not to be, then at one time there could have been nothing in existence.
4. If there was a time when nothing was in existence, then even now there would be nothing in existence because that which does not exist only begins to exist by something else already existing.
5. Therefore, not all beings are merely possible.
6. There must exist something, the existence of which is necessary.
7. This necessary being must have of itself its own necessity, and not receiving it from another.
8. This necessary being is God.



The Argument from Degree, or The Perfect One

The Argument from Degree is St. Thomas Aquinas’ Fourth Way, in which the qualities of all things are judged by something else.

An interpretation of his argument goes as follows:

1. Everything that exists has certain qualities, such as whiteness, greatness and goodness.
2. Among beings, there are some that are more or less of certain qualities, such as: more or less good, true, great, tall, large and hot.
3. For something to be more or less of a certain quality, there must exist something that is the ultimate of that quality, such as: the hottest, the largest, the best, the tallest, and the whitest.
4. If anything is great, there must exist something that is the greatest. If anything is hot, there must exist something that is the hottest. If anything is good, there must exist something that is the most good.
5. Among things in existence, anything which seems to contain the greatest of a certain quality will eventually be replaced by another thing that contains an even greater of that certain quality. 6. There must exist something which expresses the greatest of all qualities by which all other things are judged and compared.
7. This being that expresses the greatest of all qualities is the Perfect One.
8. The Perfect One is God.


The Intelligent Designer

The Intelligent Designer is St. Thomas Aquinas’ Fifth Way. A similar philosophy is found in Paley’s Teleological Argument. This argument suggests that all things must be designed by an intelligent designer. The main idea of this argument is that there exists so much intricate detail, design, and purpose in the world that we must suppose a creator. All of the sophistication and incredible detail we observe in nature could not have occurred by chance. By observing the fulfillment of purpose in nature, the teleological argument moves to the conclusion that there must be a designer.

An interpretation of this argument goes as follows:

1. There are things which lack intelligence.
2. Nevertheless, these things act for an end, by acting in the same way, so as to obtain the best result.
3. It is by design that they act in such a manner as to achieve their end.
4. Whatever lacks intelligence cannot move toward an end on its own. It must be directed by some being endowed with knowledge and intelligence.
5. Therefore some intelligent being exists by whom all things are directed to their end.
6. This Intelligent Being is God.

Another way of stating the argument is as follows:

1. Human artifacts are products of intelligent design.
2. The universe resembles human artifacts.
3. Therefore, the universe is a product of intelligent design.
4. But, the universe is complex and gigantic in comparison to human artifacts.
5. Therefore, there probably is a powerful and vastly intelligent designer who created the universe.
6. This intelligent designer is God.