How Does St. Thomas Aquinas Argue for God’s Existence?
Question: I have heard about Aquinas’ five proofs for the existence of God years ago and I never really understood them. Would you be able to explain them and briefly comment on them? Are they still relevant today?
Answer: Thanks so much for your question. If I were teaching this as a class, I would list this under the section De Deo Uno (“About the One God.”) Basically, Aquinas states the following:
Aquinas’ concept of De Deo Uno (On the One God) is a foundational element in his theology, particularly as it is presented in the first part of his magnum opus, the Summa Theologiae. This concept focuses on the existence and nature of God as the one, singular divine being. Aquinas provides five ways (quinque viae) to demonstrate the existence of God, which are philosophical arguments based on observation of the natural world. These arguments are:
- The Argument from Motion: Everything in motion must be moved by something else. This leads to a First Mover, which is God.
- The Argument from Causation: Every effect has a cause, and this chain of causes cannot regress infinitely. Thus, there must be an Uncaused Cause, which is God.
- The Argument from Contingency: Contingent beings exist, but if everything were contingent, there would have been a time when nothing existed. Therefore, there must be a Necessary Being that has always existed, which is God.
- The Argument from Perfection: There are varying degrees of perfection in the world. These degrees imply the existence of a supreme perfection, which is God.
- The Argument from Design: The order and purpose observed in the world imply a Designer, which is God.
Let’s explore each of the quinque viae a bit more, shall we?
- The Argument from Motion (or Change): Aquinas posits that everything in motion is moved by something else, ultimately necessitating a Prime Mover or Unmoved Mover, which he identifies as God. This argument’s relevance is often debated today, especially with advances in physics that offer natural explanations for movement and change. However, the argument still holds philosophical weight for those who seek a first cause beyond empirical observation.
- The Argument from Causation: This proof claims that every effect has a cause, and that an infinite regress of causes is impossible, so there must be a First Cause — God. Some find this argument resonates with modern cosmology, as the Big Bang suggests a point of origin. However, whether this “beginning” necessitates a divine cause is open to interpretation. Many still find the philosophical depth in Aquinas’ rejection of an infinite regress compelling.
- The Argument from Contingency: Aquinas observes that everything in existence is contingent — it depends on something else for its existence. Thus, he posits the existence of a necessary being, a non-contingent cause that exists by necessity — again, God. This argument has modern relevance in existential philosophy and theology, as it explores the notion of dependency versus necessity.
- The Argument from Degree: Aquinas notes that we judge things as more or less good, true, noble, etc., implying a standard of perfection by which all else is measured. He concludes that there must be an ultimate source of all perfections. While some critique this as a subjective view of value, it remains relevant for discussions about absolute standards, ethics, and the existence of transcendent qualities.
- The Teleological Argument (Argument from Design): This proof argues that the apparent order and purpose in nature imply an intelligent designer. With developments in biology, particularly Darwinian evolution, the argument has been reinterpreted and challenged. Nonetheless, it’s still persuasive for many in light of the fine-tuning of the universe and the intricate complexity observed in natural laws.
As for the question of whether the quinque via are still relevant today, each proof brings a unique angle, inviting believers, agnostics, and atheists to consider the implications of existence, causality, and purpose. Although some elements may appear outdated or incomplete by modern scientific standards, the Five Proofs continue to bridge faith and reason and simply make sense!
What Does Aquinas Say God Is Like?
Question: As a follow-up question, what are the attributes of God according to Saint Thomas Aquinas?
Answer: Thanks for your questions! I always love, as we said before, to discuss the most basic aspect of theology, namely God Himself. Aquinas’ concept of De Deo Uno is a systematic exploration of the existence and nature of God as one, simple, perfect, infinite, immutable, and omnipotent being. It serves as the basis for understanding the divine attributes and the relationship between God and creation. Here are the qualities of God; Thomas discusses these in his works Summa Theologica and Summa Contra Gentiles, although they are discussed in some of his other works as well:
God’s Simplicity
Aquinas argues that God is absolutely simple, meaning God is not composed of parts. God’s essence is identical to His existence (esse). This simplicity entails that God is pure act (actus purus), without potentiality, and that His attributes (e.g., goodness, wisdom, power) are identical with His essence.
God’s Perfection
God is infinitely perfect. Since God is the cause of all perfections found in creatures, He must possess those perfections in the highest degree. God’s perfection encompasses all conceivable perfections, making Him wholly complete and lacking in nothing.
God’s Infinity
God is infinite, not in the sense of being spatially unlimited, but in being unlimited in being and perfection. God’s infinity follows from His simplicity and perfection. As an infinite being, God transcends all categories of finitude and limitation.
God’s Immutability
God is unchanging because change implies potentiality, and God is pure act without any potentiality. God’s immutability means that He does not undergo any change in His essence, knowledge, will, or actions.
God’s Unity
Aquinas holds that God is one in an absolute sense. This unity means there is only one God, without division or multiplicity. The unity of God is derived from His simplicity; since God is not composed of parts, He is indivisibly one.
God’s Omnipresence
God is present everywhere, not by being a part of every place, but by His power, knowledge, and essence. God’s omnipresence means that He sustains and governs all things in existence.
God’s Omnipotence
God is all-powerful, meaning He can do all things that are logically possible. God’s omnipotence does not mean He can do the logically impossible (e.g., make a square circle), but it affirms that He can do all things that do not involve a contradiction.
God’s Omniscience
God is all-knowing. He knows all things, both actual and possible. God’s knowledge is not discursive (i.e., not through reasoning) but intuitive and immediate, encompassing all of time and space simultaneously.
God’s Will and Love
God’s will is perfectly free and always in accord with His nature. God wills Himself as the highest good and wills creatures as a reflection of His goodness. God’s love is the willing of good for others, and He loves all creation by willing their good and perfection.
About Rev. John P. Cush, STD
Thank you, Fr. Cush. Your clear and concise words/explanations are helpful to us who must sometimes explain such concepts to others.
You are so correct in affirming the relevance of St Thomas’s proofs. In fact especially the first two dealing in motion and causality are very much “scientific” and not only philosophical. As a professional physicist, if I were to say that something simply was and had no identifiable cause, I would be laughed at. Dr. Edward Feser has written some very clear and compelling expositions explaining and expanding on these matters. I encourage anyone interested to investigate his work.