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Aquinas' fifth way and presuppositional apologetics

Updated: Jul 2, 2022

In a recent discussion on the third man podcast, it was sometimes mentioned by the party representing Thomism that Aquinas' fifth way is the same (or not materially different) than Van Til's (or might I say Biblical) idea that all things are absolutely dependent on God for their meaning and their existence. However, I believe there is a significant difference between what Van Til meant when he wrote that every fact is dependent for its existence and meaning on the all-controlling plan of God, and what Aquinas meant in his fifth way.

Aquinas' five ways, basically summarised, take the following form: It begins with man’s knowledge from sensation and then, to account for the facts of sensation, find a sufficient reason for them in the existence of God [1].

Aquinas' fifth way illustrated
The fifth way: "as the arrow is shot to its mark by the archer."

Aquinas' fifth way

To quote Aquinas verbatim when he provides the fifth way in his Summa Theologica:

The fifth way is taken from the governance of the world. We see that things which lack intelligence* (such as natural bodies) act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result.
Hence it is plain that not fortuitously (by chance), but designedly, do they achieve their end.
Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer.
Therefore, some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

* Intelligence means the ability to choose between or to discern.

Britannica summarises the fifth way as follows:

Aquinas’s fifth and final way to demonstrate God’s existence is an argument from final causes, or ends, in nature (teleology). Again, he drew upon Aristotle, who held that each thing has its own natural purpose or end.
Some things, however—such as natural bodies—lack intelligence and are thus incapable of directing themselves toward their ends. Therefore, they must be guided by some intelligent and knowledgeable being, which is God.

Britannica, The Five Ways

The doctrine of the providence of God

The Reformed doctrine with regards to our subject matter can be summarised as follows:

Our self-contained God is the final reference point of everything created. On account of his counsel, creation, control, governance, and providence as well as his interpretation, every fact as well as the plan of the universe is precisely what it is.

H.G Stoker, Jerusalem and Athens

Similarly, article 13 of the Belgic confession states:

We believe that this good God, after creating all things, did not abandon them to chance or fortune but leads and governs them according to his holy will, in such a way that nothing happens in this world without God’s orderly arrangement...

Article 13, Belgic Confession

Van Til's Reformed position (without saying whether it disagrees with the fifth way) can therefore be stated as follows:

By God's creative work and His providence, all things are created and maintained in their existence and their operation in relation to each other. There are no maverick molecules. Everything depends on God for its existence and for its meaning.

Basic differences

Now, some Thomists today consider themselves to be Reformed. So, they would hold to both Aquinas' fifth way and the words of the confession. But, as we'll see, the starting point of the fifth way pleads ignorance with regards to whether there is a Creator-sustainer or not, hence, the starting points of Aquinas' and Van Til's respective projects are different.

The basic difference between Aquinas' approach and Van Til's approach, is that the former is a bottom-up approach, and the latter is a top-down approach.

For Aquinas, the natural man starts with mere existence. There is no concreated or innate knowledge of God within the constitution of man. Therefore, the fifth way starts by observing nature and observing that the objects of nature seem to have an inherent telos (an intentional actualisation of potential). Since these things lack intelligence, it means that they are incapable of directing themselves to actualise their potential. Therefore, like an arrow follows the path as determined by the archer's placement, the objects of nature must be directed by an intelligence which we then call God.

For Van Til, the revelation of God in man and around man is inescapable. As soon you take your first breath, you know yourself in relation to your Creator. Every aspect of your being, life and environment is pre-interpreted by God. You, like the objects of nature, are fully dependent on the creative plan of God for your existence and meaning. That you are living in God's created world as God's created image-bearer is clear from the start of your life. Therefore, since this is God's world and you are God's creature, the objects of creation will sustain the relationships that God determined them to have - and this provides us with a surefire foundation for future scientific exploration as we work to subdue and rule over creation as God has intended for us to do.

The arrow and the archer

Aquinas' arrow example is useful. For Van Til and Aquinas, the archer would be analogous to God (Creator). The arrow would be analogous to creation.

Aquinas starts off his argument by being ignorant of the archer. He then observes that the arrow is following a nicely determined path. From experience, Aquinas knows that objects that lack intelligence cannot move as such. He also observes that multiple arrows nearly always follow the same path to hit the target. Therefore, the arrow(s) required intelligence that caused and guided the movement.

Van Til starts off his argument by intimately and inescapably knowing the archer. Knowing the archer, Van Til, based on the words that the archer has told him (revelation), knows that the arrows not only have but will continue to follow the pre-defined path as the archer has determined it - even if the archer were to decide to aim at a different target altogether, it would not frustrate him.

A critique of Aquinas' fifth way

There are many questions that can potentially be raised against the fifth way.


Aquinas observes that objects with no intellect "act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result". Since these objects lack intellect, it means they cannot discern or choose to always act in this way. Since they "always" or "nearly always" act in the same way without the ability to choose to act in this way, it cannot be due to chance that they act this way. Hence, they must be directed by a being with intelligence that we call God.

An interesting concession that Aquinas makes is that the objects don't always act in the same way, but merely nearly always. The question is why there are cases where the objects don't act in the same way, and whether in these cases it is also by design or by chance?

More concerningly for the argument, just because the objects of nature have for the known past always acted in a consistent way toward an end, it does not mean that they will continue to do so. It, therefore, does not make sense to infer God from merely observing that nature has acted consistently in the past. It might cease doing so in the future because of chance. Perhaps the way nature acts now is due to chance? Perhaps it's due to chance that they remain consistent in the way they act? If the Thomists were to disagree by stating that Aquinas clearly rules out chance, it must be pointed out that he only rules out chance because of the perceived regularity in nature. He infers that there must be a Creator and not a principle of chance at work. However, starting with observation, it's an open question whether a Creator exists or not. Chance might still reign supreme.

Another, more intuitive, way to see why the argument is unconvincing for me, is that the Christian must admit that it is possible for God to make an axehead float (work differently in the objects of Creation at different points in time). An axehead floating is not a predictable result we would expect based on past experiences. Moreover, it is possible that God could make an axehead float without necessarily revealing to us that He has done so (as in the case of 2 Kings 6, when God made an axehead float for Elisha). In this case, we would no longer observe nature acting consistently and the argument would fall apart.

If we don't start with a view of nature as God-dependent, with ourselves as God-dependent, and with nature sustaining the relationships that God intended, the only conclusion for Aquinas' fifth way must be that chance might reign supreme, and the Christian God might not (notice that I intentionally reversed the order to show the same conclusion from another side). Or, at the very best, that it is highly probable based on past experience that God is at the back of the purposes in nature. The basic error of the fifth way is, therefore, that it treats nature as a self-contained system that can be known without revelation from God.

Eve thought she could do just fine without special revelation even in the pre-fall garden. The result was the most devastating event in the history of mankind. It's no different today.

Some intelligent being that probably exists?

A further critique of the fifth way is found in an envisioned conversation between Mr Grey and Mr Black as written by Van Til. Mr Grey was an Arminian, and Mr Black an unregenerate man.

Mr Grey offers Mr Black the following argument:

But just now I am only asking you to admit that there is a great accumulation of evidence of the sort that any scientist or philosopher must admit to be valid for the existence of a God back of and above this world.
You see this watch. Isn’t it highly probable that a power higher than itself has made it? You know the purpose of a watch.
Isn’t it highly probable that the wonderful contrivances of nature serve the purpose of a god? Looking back we are naturally led to a god who is the cause of this world; looking forward we think of a god who has a purpose with this world. So far as we can observe the course and constitution of the universe there is, I think, no difficulty on your own adopted principles, against belief in a god.
Why not become a theist? You do want to be on the winning side, don’t you? Well, the Gallup poll of the universe indicates a tendency toward the final victory of theism.

Mr Black's answer is devasting and preys on the failure of Mr Grey to have the correct starting point in his apologetic. Mr Black answered Mr Grey:

You speak of evidence of rationality and purpose in the universe. You would trace this rationality or purpose back to a rational being who is back of the universe who, you think, is likely to have a purpose with the universe.
But who is back of your God to explain him in turn? By your own definition your God is not absolute or self-sufficient. You say that he probably exists; which means that you admit that he may not exist. Probability rests upon possibility. I think that any scientific person should come with an open mind to the observation of the facts of the universe. He ought to begin by assuming that any sort of fact may exist.
I was glad to observe that on this all-important point you agree with me. Hence the only kind of god that either of us can believe in is one who may or may not exist. In other words, neither of us does or can believe in a God who cannot not exist.
It was just this sort of God, a God who is self-sufficient, and as such necessarily existent, that I thought you Christian theists believed in?

This brings out the difference between Aquinas in his fifth way and Van Til more clearly: Either one presupposes God back of the ideas of possibility or one presupposes that the idea of possibility is back of God. Either one says with historic Reformed theology on the basis of Scripture that what God determines and only what God determines is possible, or one says with all non-Christian forms of thought that possibility surrounds God [2].

For Aquinas, even though the facts of experience in their telos might (currently) lend themselves toward the idea that God is at the back of their purpose, they might stop behaving as such in the future, and the fifth way would fall apart. It remains an open possibility if it is not presupposed that God is at the back of all possibilities.

Van Til, in another context, makes the same point as follows: If the facts of the universe surrounding man are what they are because they reveal the creative-redemptive activity of God, then how can one rightly argue whether God is back of them? A child does not ask whether the furniture of the house in which he lives belongs to his father. So a creature who knows that he is a creature cannot consistently ask whether the facts that he sees are created by God.

It is only the sinner who wants to retain his sinful independence who can ask this question. Natural theology presupposes the actual or at least the possible independence from God of the facts that he meets with in his daily experience. But to admit that these facts could even possibly be anything but created by God is to insult God. There is no such thing as possibility except for the plan or purpose of God. Natural theology first envelops God in infinite mystery and then asks whether he is the light of men [3].

A further, more devastating critique is found in Mr Black's second paragraph. If God is at the back of this universe to explain it, who or what is at the back of God to explain Him? Since from the fifth way it is probable that God may not exist (which is the same as saying that it is probably that God may exist), it means that it is possible that God might not exist. What then, is the source of possibility and impossibility if it is not God Himself?

Therefore, in making the non-existence or existence of God a mere possibility, the Thomist apologist has effectively ceased to argue for God who cannot not exist. Any God he manages to prove with high probability is not the self-contained God of the Bible. The self-contained God of the Bible is the sole determiner of possibility and impossibility. He is the one who meets man everywhere - He is inescapable. We've offended Him, and He is offering us redemption in Jesus Christ.

Multiple intelligent beings

The fifth way also seems to be compatible with multiple probably intelligent beings that guide nature.

Aquinas' fifth way redeemed

The reason the fifth way is convincing is not because of the "airtight logic" or the neutral starting point of the argument. It's despite those things.

Nature acts in accordance with the all-encompassing plan of God. From the point of Creation up until eternity, God will be in complete control. Nature is absolutely dependent on God for its meaning and existence.

If we think of nature as a self-contained independent system, it doesn't change the fact that God in His providence and goodness has created a world for us which He governs with a certain predictable regularity and irregularity that makes life interesting and fun. There are no givens for God, and there is no principle of chance that can subvert His purposes.

This means that when unbelievers live in God's world, they too enjoy God's providential government of this world, but they refuse to give thanks to God. Instead, they view nature as self-existent and self-contained. God is excluded from the start of their reasoning process.

When Aquinas develops his fifth way, he believes himself to start from a neutral perspective. But, as we've shown, this cannot get us the Christian God. It necessarily entails a finite god that may or may not exist. The fifth way, I think, preys on the actual state of affairs. God is in control. People know God is in control. Therefore, despite the inconsistencies of the fifth way, it feels persuasive because it strikes something deep within us, that the facts of experience are not brute facts. We aren't the determiners of our own destiny. The rains that come (or don't come) on the clouds are not due to chance. There is inherent meaning in the world.

The fifth way can be redeemed by going top-down instead of bottom-up: God is in control. Due to His providence, we can live consistent and predictable, yet not boring lives in God's world. If you reject this, your only other appeal is chance, and there can be no such thing as knowledge in a world that is driven by chance and related by chance. It is Christ or chaos.


[1] Cornelius Van Til and Eric H. Sigward, The Pamphlets, Tracts, and Offprints of Cornelius Van Til, Electronic ed. (Labels Army Company: New York, 1997).

[2] Pilgrim. 2022. A Defense of Reformed (biblical) Presuppositional Apologetics by Cornelius Van Til. [ONLINE] Available at: [Accessed 25 April 2022].

[3] Cornelius Van Til and Eric H. Sigward, The Pamphlets, Tracts, and Offprints of Cornelius Van Til, Electronic ed. (Labels Army Company: New York, 1997).

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Feb 26, 2023
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Thanks for writing this article. I always wondered whether Aquinas' fifth way is compatible with the presuppositional view of apologetics. I think I now understand why it isn't. I presumes upon God's faithfulness.


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