According to the Christian philosopher Peter Kreeft, and many others, Aquinas gives five different arguments for the existence of God.  In the Handbook of Christian Apologetics (IVP, 1994; hereafter: HCA) by Peter Kreeft and Ronald Tacelli, there is a chapter that lays out twenty different arguments for the existence of God, and the first five arguments are versions of Aquinas’ Five Ways:

A word about the organization of the arguments.  We have organized them into two basic groups: those which take their data from without–cosmological arguments–and those that take it from within–psychological arguments.  The group of cosmological arguments begins with our versions of Aquinas’ famous “five ways.” (HCA, p.49)

Kreeft is Catholic, so it is not surprising that he puts these arguments by Aquinas at the front of his list of arguments.  On pages 50 through 58 of HCA, Kreeft and Tacelli lay out five different arguments for the existence God that they take to be versions of five different arguments for the existence of God presented by Aquinas in Summa Theologica (Part I, Question 2, Article 3: Whether God Exists?).

I believe, however, that Kreeft and Tacelli are WRONG on this point, and that Aquinas has only ONE argument for the existence of God, or possibly TWO arguments.  I will need to study the details of Aquinas’ case for God a bit further in order to make a final determination on whether he has ONE argument or TWO arguments for God.  (Note: This alternative way of understanding the Five Ways passage is presented by Knut Tranoy in A Critical History of Western Philosophy; see pages 110-112).

Kreeft and Tacelli, I suspect, were deceived by the misleading title of the famous Five Ways passage in Summa Theologica:  “Whether God Exists?”.   Since Aquinas gives five different arguments in that passage, this makes it seem as though he was giving five different arguments for the existence of God.  But this is a gross distortion and a serious misunderstanding of the Five Ways passage.  There are exactly ZERO arguments for the existence of God in the Five Ways passage.

The problem is that Aquinas does not define what he means by “God”, and that what he apparently means by “God” is NOT what the word “God” means in the English language, especially in relation to the Christian religion and Christian theology.  So, in the Five Ways passage, Aquinas does NOT argue for the existence of “God” in the ordinary sense of the word, as used by Christian believers and Christian philosophers and apologists.

The word “God” is a proper noun, the name of a single being.  The meaning of this name is based on a definite description, a list of properties or characteristics that (allegedly) belong to one, and only one, person.  A bare-bones definite description of this person would include the following properties (at least in relation to the use of the word “God” by Christian believers, and especially Christian philosophers and apologists):

• the creator of the universe
• an eternally bodiless person
• an eternally omnipotent person
• an eternally omniscient person
• an eternally perfectly morally good person

Although the ordinary use of the word “God” probably does not entail the possession of each and every one of these properties by the being in question (because the ordinary use of famous names typically is criterial  and thus allows some wiggle room, allowing the name to be properly applied so long as the being in question possesses MOST of the properties in the definite description and no other being possesses MOST of the properties), it is clearer, logically cleaner, and more theologically conservative to treat the list of properties in this definite description as necessary conditions for the proper application of the name “God” to a particular being, and to take them jointly as a sufficient condition for the proper application of the name “God” to a particular being.

What Aquinas actually argues for in the Five Ways is the following five metaphysical claims:

(MC1) There exists an AP being.  

(“an AP being” = a being that is actus purus, i.e. pure act)

(MC2) There exists an FEC being.  

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

(MC3) There exists an IES being.

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

(MC4) There exists a COP being.

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

(MC5)  There exists an IDN being.

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

Aquinas goes on in OTHER passages of Summa Theologica to use (MC3) as the basis for an argument for the existence of God (in the ordinary sense of the word that I have outlined above), and one could argue that he has a second argument for the existence of God that is based on (MC1).  Each argument can be summarized as a modus ponens that contains a metaphysical claim as the first premise and a conditional claim that links the metaphysical claim to the existence of God:

THE IES ARGUMENT

(MC3) There exists an IES being.

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

Therefore:

(G) God exists.

THE AP ARGUMENT

 (MC1) There exists an AP being.

(CC2) IF there exists an AP being, THEN God exists.

Therefore:

(G) God exists.

It might be the case that Aquinas intended for the two key metaphysical claims to function together in a single argument for God (or possibly although this was not his intention, this might be an improved way to make use of Aquinas’ reasoning about God to formulate an argument for the existence of God):

THE COMBINED IES & AP ARGUMENT

(MC6)  There exists a being that is both an IES being and an AP being.

(CC3) IF there exists a being that is both an IES being and an AP being, THEN God exists.

Therefore:

(G) God exists.

Whether Aquinas gives ONE argument or TWO arguments for the existence of God, it is clear that the Five Ways passage contains arguments for only five metaphysical claims, and contains ZERO arguments for the conditional claims in the above modus ponens arguments for the existence of God.  Crudely speaking, the Five Ways passage is concerned with only HALF of Aquinas’ argument for the existence of God: the metaphysical claim but not the conditional claim.

But, more accurately, MOST of Aquinas’ reasoning about the existence of God is found in later sections of Summa Theologica that contain a lengthy and complex chain of reasoning consisting of four or five phases (see  post 2 of the I Don’t Care series for a chart that lays out the phases) in order to support the conditional claim(s) in the above argument(s).  So MOST of Aquinas’ argument for the existence of God is found OUTSIDE of the Five Ways passage.

Each of the conditional claims in the above modus ponens arguments is a summary of a lengthy and complex line of reasoning by Aquinas and can be broken down further into a series of conditional claims of the following form:

(P1) If there exists a being with property W, then there exists a being with properties W & X.

(P2) If there exists a being with properties W & X, then there exists a being with properties W & X & Y.

(P3) If there exists a being with properties W & X & Y, then there exists a being with properties W & X & Y & Z.

Therefore:

(P4) If there exists a being with property W, then there exists a being with properties W & X & Y & Z.

(P5) If there exists a being with properties W & X & Y & Z, then God exists.

Therefore:

(CC) If there exists a being with property W, then God exists.

Aquinas provides reasoning in support each of the conditional claims in this more complex argument, but he does so OUTSIDE of the Five Ways passage.  Thus, MOST of the reasoning that Aquinas provides in support of the existence of God is OUTSIDE of the Five Ways passage.

This means that Kreeft and Tacelli (and many others as well) have completely misunderstood Aquinas’ argument(s) for the existence of God and have only touched upon a small portion of the actual reasoning that Aquinas puts forward for the existence of God in Summa Theologica.

Given this point of view, let me re-state and clarify the meaning of the title of this series of posts:

I DON’T CARE about the first five arguments in Chapter 3 of HCA by Peter Kreeft and Ronald Tacelli, because those arguments are gross distortions and serious misunderstandings of the actual argument(s) for the existence of God given by Aquinas in Summa Theologica.

HOWEVER, I am very much interested in the actual argument(s) that Aquinas gives for the existence of God in Summa Theologica, and I plan to study his reasoning on this issue more closely and then present it in greater detail in future installments of this series.