The famous Five Ways passage by Aquinas in Summa Theologica does not contain five arguments for the existence of God. Rather, it contains ZERO arguments for the existence of God.  There is actually only one argument for the existence of God in the Summa Theologica, and the reasoning in the Five Ways passage only represents a tiny piece of that very long and complicated argument.

The Five Ways passage presents arguments for these five metaphysical claims:

(MC1) There exists a UFC being.  

(“a UFC being” = a being that is an unchanged first changer – often misleadingly translated “unmoved first mover” )

(MC2) There exists an FEC being.  

(“an FEC being” =  a being that is a first efficient cause)

(MC3) There exists an FN being.

(“an FN being” = a being that is a first necessary being, a being that is necessary but does not get its necessity from another being)

(MC4) There exists a COP being.

(“a COP being” = a being that is the cause of all perfections)

(MC5)  There exists an IDN being.

(“an IDN being” = a being that is an intelligent designer of nature)

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NOTE:

The above list of five metaphysical claims is a revised version of the list of five metaphysical claims that I spelled out in Part 3 of this series of posts.   There are two key metaphysical claims by Aquinas that are derived from one or more of the above five metaphysical claims, but I jumped the gun by including those two key claims in the previous list of five metaphysical claims that Aquinas argues for in the Five Ways passage.  The two additional key metaphysical claims are argued for by Aquinas in other passages that occur later in Summa Theologica:

(MC6) There exists and IES being.

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

(MC7) There exists an AP being. 

(“an AP being” = a being that is actus purus, i.e. pure actuality, with no potentiality)

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Aquinas’ argument for the existence of God can be summarized this way:

(MC6) There exists an IES being.

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

Therefore:

(G) God exists.

The Five Ways passage comes close to providing an argument for (MC6), but some additional reasoning is required.  The Five Ways passage, however, makes no attempt to prove the conditional claim (CC1).  Several (at least a dozen) other passages in Summa Theologica provide a long and complex line of reasoning in support of (CC1), as we shall see.

I had initially thought that I would use the strategy of working backwards from the main conditional premise that Aquinas needs to support:

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

The argument for (CC1) needs to be something like this:

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.

I was planning to work backwards from various conditional claims linking the existence of an IES being to the existence of an IES being with a divine attribute:

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

However, Aquinas’ argument for the existence of God is even more lengthy and complicated than I first thought, so it is a bit discouraging to use the strategy of working backwards from (CC1) to reconstruct his reasoning.  So, I am changing my strategy, and I will be starting in the MIDDLE of his reasoning and working my way both forward, to arrive at the conditional claim (CC1), and backwards to the initial five metaphysical claims made in the Five Ways passage.

The middle of Aquinas’ reasoning occurs when he shifts from discussion and argument about abstract metaphysical properties of God to the more recognizable religious properties of God.  The core religious property of God is KNOWLEDGE, in Aquinas’ view, and this religious property is derived from the metaphysical property of IMMATERIALITY (although I include “eternally bodiless person” as a basic defining divine attribute).

Here is the passage where Aquinas makes the shift from the derived metaphysical property of IMMATERIALITY to the core religious property of KNOWLEDGE:

I answer that, In God there exists the most perfect knowledge. … Therefore it is clear that the immateriality of a thing is the reason why it is cognitive, and the mode of knowledge is according to the mode of immateriality. … Since therefore God is in the highest degree of immateriality, as stated above (Q. VII, A. 1), it follows that He occupies the highest place in knowledge.

(Summa Theologica, Part I,  Question 14, Article 1: Whether There is Knowledge in God?)

By starting in the middle of Aquinas’ reasoning, I break the complex task into two main pieces: (1) working backwards from the conclusion that an IES being is IMMATERIAL to the metaphysical claims made in the Five Ways passage, and (2) working forward from the conclusion that an IES being has PERFECT KNOWLEDGE to the derived religious/theological properties of God:  the creator of the universe, an eternally omniscient person, and an eternally perfectly morally good person.

The religious property of omnipotence is derived not from PERFECT KNOWLEDGE but from some of God’s metaphysical properties.  So, I will also have a third task: (3) working backwards from the existence of an eternally omnipotent person to the metaphysical claims made in the Five Ways passage.

Since being IMMATERIAL appears to imply that God is bodiless, if I can trace the reasoning for the claim that an IES being is IMMATERIAL backwards to the metaphysical claims in the Five Ways passage, then that will cover the property of being bodiless (though Aquinas needs to show that God is eternally bodiless, so some additional reasoning will probably be needed).

The following diagram shows the general flow of the reasoning (click on the image below for a clearer view of the diagram):