In the thirteenth century, a monk named Thomas Aquinas proposed five ways (or, in Latin, Quinquae Viae) of reasoning to prove the existence of God. Utilizing evidence from nature and theological/ philosophical reason, Aquinas created arguments that have had a lasting impact on countless people.
Aquinas’ five ways of proving the existence of God remain a highly influential set of arguments in philosophy and theology to this day. As a part of Aquinas’ “Summa Theologica,” the five ways are a staple of logical arguments for God’s existence.
The Five Ways
- The First Way: Motion
- The Second Way: Efficient Cause
- The Third Way: Contingency
- The Fourth Way: Degrees
- The Fifth Way: Design
The Cosmological Structure of The Five Ways
The first four of Aquinas’ arguments are cosmological in nature. A cosmological argument suggests that everything in existence has a cause or a creator, if you will. Consequently, If a universe exists, there must be a cause to account for its existence, a “first cause” that is itself uncaused. Some, like William Lane Craig, say this cause needs to be outside of the universe, eternal, independent, and powerful enough to create the universe. The only logical choice to account for this cause is a supreme being, which we call God.
The Infinite Regress Problem
The reason behind this requirement for a “first cause” lies in a philosophical problem called an infinite regress. Imagine you had an infinite line of dominoes all tumbling down one after the other. Each individual domino falls because the one behind it collides with it.
However, if every domino falls because the one behind it caused the falling, how did the chain of collisions even begin? After all, in order for the chain of collisions to start, someone at some point in time would need to have knocked over the first domino. Otherwise, we would have a line of standing dominoes, not falling.
Similarly, if everything has a cause, then everything will have to have been caused by something. This chain of causes will go back forever, leading us to wonder how the chain even got started in the first place.
Although some speculate that an infinite regress could theoretically be possible, Aquinas wasn’t on that train, which is reflected in the cosmological nature of his arguments.
The Teleological Argument in The Five Ways
His final argument, the fifth way, is, in essence, a Teleological position. In this argument, he explores the purposeful design of the universe to find the intelligent designer at its core. This argument also has some connections to his views on Natural Law.
1. The Argument From Motion
One of Aquinas’ first arguments revolves around the concept of motion. He reasoned that since everything that moves must have been impacted by something else, there must be an “Unmoved Mover” who kick-started the chain of events. Otherwise, you fall into an Infinite regress of movers.
“It is certain, and evidence to our senses, that some things are in motion. Now whatever is moved is moved by another. …If that by which it is moved be itself moved, then this also must needs to be moved by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover, seeing that subsequent movers move only inasmuch as they are moved by the first mover: as the staff moves only because it is moved by the hand. Therefore it is necessary to arrive at a first mover, moved by no other; and this everyone understands to be God.”
2. The Argument From Efficient Cause
His second argument plays off the first; however, instead of focusing on the observable movement of the universe, he homes in on the existence of causation.
According to Aquinas, everything that exists was brought into the world by something other than itself. The trees you see around you were first genetic information randomly scattered by the wind and insects. Likewise, You were created when on random sperm cell found its way to your mothers’ egg. Nothing in creation can bring itself into existence—consequently, everything has a cause. If you trace, these causes back far enough; you will find an initial “First Cause,” which, to prevent an infinite regress, must itself be uncaused. Aquinas claimed this first cause is God.
“There is no case known (neither, indeed, is it possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which would be impossible. Now in efficient causes it is not possible to go on to infinity …Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.”
3. The Argument From Contingency
Building once again on these first two arguments, Aquinas supported the existence of God by citing the concept of necessary and contingent beings. He maintained that everything in the universe is contingent and can be reduced to nothing, while God is an essential being, existing without any prior cause.
Contingent beings can be categorized as anything with the ability not to exist. So, you and I are contingent beings, while God, who is eternal, is a necessary being. Other things like rocks would also be contingent since they at one time did not exist. According to Aquinas, if it’s possible for contingent things not to exist, then it’s also possible, if not probable, for a world made up of contingent things to never come into existence. Therefore, he concluded that the source of all contingent beings is the necessary being—God.
4. The Argument From Degrees (Gradation)
In his fourth argument, Aquinas reasoned that since quality or good exists in the universe, there must be a source or standard by which all good can be measured.
His idea comes from our proclivity towards determining the quality of something by comparing it to other similar things. Good things can not be defined as good in isolation. Its quality can only be seen when measured against or compared to a similar or opposite thing.
For example, we determine the day’s temperature by observing how close it gets to the boiling or freezing point of water. The closer the temperature gets to water’s boiling point, the hotter the day becomes. We use these two anchors as a standard that helps us make sense of and talk about temperature.
Similarly, we judge the quality of things by measuring them against a prime example.
For instance, the quality of a runner is determined by the track and field stars of the past. How close they consistently get to records set by the best tell us how good they are. And if they manage to break a record, they become the new standard for peak athletic quality.
Consequently, if there is to be any meaningful definition of good, quality, or perfection, then there has to be a standard that everything can be measured against. Aquinas believed this standard was God.
“For if each one [thing] were of itself competent to have it [the positive property], there would be no reason why one should have it more than another.”
5. The Argument From Design
The next argument steps away from the cosmological and presents a teleological perspective. Thomas Aquinas’ fifth way of proving God’s existence is an argument based upon the universe’s natural order. He states, “That the fifth way is taken from the governance of the world.”
According to Aquinas, everything in the universe is designed to accomplish some kind of task or fulfill some end. Dogs have noses designed for hunting, fish have bodies designed for swimming, and you have a mind designed for thinking. He reasoned that nothing in the universe is intelligent enough to design itself with an end goal in mind. Consequently, there must be an intelligent designer.
“Now whatever lacks knowledge cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is directed by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.“
He also looked around the world and saw that organization is apparent in most living and nonliving things. Highly complex phenomena such as the changing of the seasons, the formation of a hurricane, and the working of the kidneys are all examples of this order in nature. These things are examples in which the end goal is reached – a goal that can’t be attributed to physical cause and effect but rather the guidance of a higher power. Aquinas argues that the ordered nature of the world indicates the existence of an ordering force, which he said is God.
Final Thoughts
Although Aquinas wrote in the medieval ages, many of his arguments are still used and explored today. His takes on the cosmological argument inspired the writings of many thinkers. Likewise, his teleological argument has seen centuries of philosophical expansion and is one of the most popular arguments for God today.
All in all, Thomas Aquinas put forward timeless and persuasive arguments for the existence of God. His ideas ranged from philosophical to theological. He explored the evidence buried in the cosmological origins of the universe and analyzed the teleological design of our planet. He cited evidence from cause and effect, motion, necessary and contingent beings, degree of goodness, and purpose of life to demonstrate the presence of God. By combining careful logic and spiritual belief, Thomas Aquinas’ five ways left a lasting impact on theology and the world that can still be felt today.
Sources and Further Reading
- California State University: Thomas Aquinas’ Five Ways to Prove the Existence of God
- Britannica: the Five Ways
- University of Notre Dame: Aquinas’ first and second ways
- Sens Homines: Aquinas’s Argument from Degrees of Perfection Part 4: Conclusion
- IEP.edu: Design Arguments for the Existence of God
- Summa Theologica
