I have previously argued that, contrary to popular opinion, there are ZERO arguments for the existence of God in the famous Five Ways passage by Aquinas in Summa Theologica (Part I, Question 2, Article 3: Whether God Exists?).

Now I’m getting into what I do care about, namely the ACTUAL argument(s) that Aquinas gives to prove the existence of God.  Here is one argument (possibly the only one) for the existence of God from Summa Theologica:

THE IES ARGUMENT

(MC3) There exists an IES being.

(CC1) IF there exists an IES being, THEN God exists.

Therefore:

(G) God exists.

(“an IES being” = a being that is ipsum esse subsistens, i.e. its own self-subisting existence) 

The argument supporting (MC3) is found in the Five Ways passage.  But the arguments supporting (CC1) are found in various OTHER passages in Summa Theologica.  

In order to successfully prove (CC1), Aquinas needs to make an argument that is something very close to the following argument:

ARGUMENT FOR (CC1)

(P1) IF there exists an IES being, THEN there exists exactly one being that is the creator of the universe, an eternally bodiless person, an eternally omnipotent person, an eternally omniscient person, and an eternally perfectly morally good person.

(P2) IF there exists exactly one being that is the creator of the universe, an eternally bodiless person, an eternally omnipotent person, an eternally omniscient person, and an eternally perfectly morally good person, THEN God exists.

Therefore:

(CC1) IF there exists an IES being, THEN God exists.

It is premise (P1) that Aquinas argues for in various other sections of Summa Theologica outside of the Five Ways passage.

Aquinas argues for the existence of an omnipotent being in Part I, Question 25: “The Power of God” (especially in Article 2).

Aquinas argues for the existence of a being has “the most perfect knowledge” in Part I, Question 14: “Of God’s Knowledge” (especially in Article 1).  This appears to be an argument supporting the view that an IES being must be omniscient.

While Aquinas does not appear to argue specifically that there exists a being that is a perfectly morally good person, he does argue for the existence of a supreme being who has the moral virtues of love and justice in Part I, Question 20: “God’s Love”, and in Part I, Question 21: “The Justice and Mercy of God” (especially in Article 1).  If Aquinas can prove that an IES being has the virtues of love and justice, then that comes close to the claim that an IES being is a perfectly morally good person.

Aquinas argues for the eternity of an IES being in Part I, Question 10: “The Eternity of God” (see Article 2: “Whether God is Eternal?”).  But even if a being exists eternally, and is omnipotent and omniscient now, that does not mean that this being will be eternally omnipotent and eternally omniscient.  So, I suspect that in order to show these (and other) divine attributes to be eternal, Aquinas has to establish that the IES being is IMMUTABLE, which he attempts to do in Part I, Question 9: “The Immutability of God”.

Aquinas argues, I believe, that there can be only ONE being that is an IES being in Part I, Question 11: “The Unity of God” (see Article 3: Whether God is One?”).

Aquinas argues for the immateriality of an IES being in Part I, Question 3: “Of the Simplicity of God.”  This would support the claim that an IES being is bodiless.

Aquinas does not have a section that explicitly argues that an IES being is the creator of the universe, but there is a section in Part I, Question 14: “Of God’s Knowledge” that appears to address this: Article 8: “Whether the Knowledge of God Is the Cause of All Things”.  In that section, Aquinas argues that “God is the cause [of natural things] by His knowledge.”

NOTE: If Aquinas argues somewhere that an IES being must also be an IDN being (the intelligent designer of nature), then the Fifth of the Five Ways could also be used to support the claim that an IES being is the creator of the universe.

So, in order to piece together Aquinas’ ACTUAL argument for the existence of God, we must study the reasoning he lays out in at least the following sections in Part I of Summa Theologica:

Question 3: “Of the Simplicity of God”

Question 9: “The Immutability of God”

Question 10: “The Eternity of God”

Question 11: “The Unity of God”

Question 14: “Of God’s Knowledge”

Question 20: “God’s Love”

Question 21:  “The Justice and Mercy of God”

Question 25: “The Power of God”

Furthermore, in order to link some of these properties back to the concept of an IES being, reasoning from other sections of Part I of Summa Theologica will also be required:

Question 4:  “The Perfection of God”

Question 7:  “The Infinity of God”

Question 19: “The Will of God”

So, in order to reconstruct Aquinas’ ACTUAL argument for the existence of God, one must study his reasoning from at least a DOZEN different sections (“Questions”) of Part I of Summa Theologica, not just the reasoning found in the Five Ways passage which is in the section called Question 2: “The Existence of God.”

No wonder most people want to interpret the Five Ways passage as presenting five arguments for the existence of God!  To try to figure out Aquinas’ ACTUAL argument for the existence of God is a royal pain in the ass.  It is so much EASIER to just grossly distort and completely misinterpret the Five Ways passage, and then quickly move on to some other topic.