What is Classical Theism? (Part 4)

Can we prove that God exists? In parts 1 – 3 of this series, I defined “proof” in terms of ‘metaphysical demonstration’ and defended the first 3 premises of an Aristotelian proof of God’s existence.

In this post, I define key terms in premises 4 and 5 of the argument. Then, I defend those premises. Before we begin, recall the argument outline:

  1. Change occurs.
  2. Change entails a distinction of actuality and potentiality.
  3. Change requires a changer, and more generally, actualization requires an actualizer.
  4. The existence of things here and now requires a hierarchically ordered causal chain of actualized potentials.
  5. Hierarchically ordered causal chains of actuality and potentiality cannot go on indefinitely, but must terminate in a first member, who is pure actuality.
  6. There exists a first mover (the first member of the chain) that is pure actuality.
  7. The first mover, existing as pure actuality, possesses the divine attributes.
  8. The first mover is God.
  9. Therefore, God exists.

Now, let’s proceed to our discussion of key terms.

Linear Chains

 Consider the arrest and detainment of a suspected armed robber. This may unfold in the following way:

  • A police chief has a warrant for a Bill’s arrest.
  • He commands officers go to Bill’s house and arrest him.
  • The officers drive to Bill’s house and arrest him.
  • The officers drive Bill to the police station.
  • Guards escort Bill to a cell where he remains until his court date.
  • On Bill’s court date, a jury convicts him.
  • The authorities escort Bill to a prison cell.

In this example, each step is causally related to the previous step. Each step follows from what happened before it. But the cause and effect relationship takes place over a long period of time, and later links in the chain are not immediately dependent on the previous events.

For instance, the police chief’s commands do not need to be present at the same time that the officers put Bill in handcuffs. The chief’s commands lead the officers to do this, but while they are doing this they do not need a constant command from the chief “Place him in cuffs, place him in cuffs, etc.” The officers maintain their own power to do so.

This represents what we might call a linear causal chain. We contrast this with the idea of a hierarchical causal chain.

Hierarchical Chains 

The book The Case for Jesus by Brant Pitre now sits on my bookshelf. The bookshelf holds up the book. If I were to remove the shelf, the book would not remain suspended in midair on its own. We can then ask a question: what holds up the shelf? (Note: I adopt this example from Dr. Feser’s lecture here).

Well, the floor of my apartment holds of the shelf. But what holds up the floor? Well, the floor is held up by the frame of the apartment building (I live on a second floor). But what holds up the frame of the building? The foundation. What holds up the foundation? The ground of the earth.

For our purposes here, we can stop the discussion at Earth. This causal chain is ordered hierarchically because each member has an immediate causal dependence on the previous member. At a moment of time, here and now, each member must exert its causal power in order for the book to be held up. If any of the members were removed or defective, then the book would not be held in place.

Imagine that we removed the frame of the house. The floor would not float. If we removed the floor, the shelf would not float. The book would immediately lose the property of “being held up” if any member of the chain is removed or becomes deficient. So, we can distinguish those causal series or causal chains ordered in a linear fashion from those ordered hierarchically.

Remember, a linear causal chain consists of members that retain their own causal power to actualize the next member even when the previous member no longer exists. In a hierarchical causal chain, each member has causal power derivatively and immediately depends on the prior member being in place in order to actualize the next member. 

A Helpful Graphic

This graphic serves to illustrate the distinction.


In a linear causal chain, the members cause future members over time and the causal dependence on the previous members is not immediate. Notice how B  goes on to cause C on its own. We can say B has “built-in” power to cause C.

In a hierarchical causal chain, things are different. B only maintains its power to cause A insofar as it derives causal power from C, which only maintains power insofar as it derives causal power from D, and so forth. There is an immediate causal dependency on prior members of the chain.

Premise 4

Returning to the main argument, premise 4 states: The existence of things here and now requires a hierarchically ordered causal chain of actualized potentials.

 Why think this is true? Take any mundane object in the universe. Dr. Feser uses a cup of coffee on pg. 26 of Five Proofs of the Existence of God. We shall consider a glass of orange juice. Consider that water makes up the majority of the orange juice. Your typical juice label lists water as the first ingredient.

The orange juice could not exist in an actualized state (i.e. it is indeed orange juice in this moment) unless the water actually existed. Given the chemical composition of the water as H2O, the molecules consist of hydrogen and oxygen.

But hydrogen and oxygen have the potential to come together in other ways. Why are they actually bonded as water here and now? At the present moment, their potential to come together as water is being actualized .

Feser points out:

You might say that it has to do with chemical bonding between atoms, but that merely rephrases rather than answers the question. For the atoms have the potential to be bonded in other ways, and yet they are not so bonded. It is their potential to be bonded in such a way that water results that is in fact being actualized. Again why? Appealing to the structure of the atom won’t answer the question either, but merely pushes it back a stage. For why are the subatomic particles combined in just the specific way they are, here and now, rather than some other way? What is it that actualizes that potential rather than another? [Five Proofs of the Existence of God, pg. 26]

As we go deeper and deeper into the reality of the orange juice, this combination of actualized potentials constitutes a hierarchically ordered chain. It’s like the book The Case for Jesus by Brant Pitre now on my shelf, held up by the floor, held up by the foundation, held up by the earth.

By examining an ordinary object, like a glass of juice, we reach the conclusion that there exists a hierarchically ordered chain of actualized potentials. Next, we consider why this chain can’t stretch back infinitely.

Premise 5

Returning to the main argument, premise 5 states: Hierarchically ordered causal chains of actuality and potentiality cannot go on indefinitely, but must terminate in a first member, who is pure actuality.

How do we know the actualization does not simply go on indefinitely? As argued previously, hierarchically ordered chains require a first member. Since each member has causal power derivatively, if there were no first member, then the secondary members would have no source to derive their power from. At some point, they would get to a previous member and have nothing before it.

How do we know it cannot regress infinitely? Or in a circle? First, even if a chain could regress infinitely or in a circular way, there is nothing to impart initial causal power to the infinite chain or circle. An infinite amount of box cars cannot move themselves down the track; they require an engine car. A circle of boxcars will not move themselves around the track either.

If there are members which only act instrumentally, then there must be a first mover to impart causal power to all of the instruments, since instruments qua instruments cannot do anything.

Pure Actuality

 We have arrived at a first member of a hierarchically ordered chain of actuality and potentiality. In order to truly be first and stop the chain, this first member cannot be a mixture of potentiality and actuality. It cannot be potentially this way or that way.  Why not?

If the first member itself were potentially this or that, then we would need a reason why a particular potentiality is actualized and not another. Something else would have to account for its actualization. In other words, it would lead us right back to the regress ruled out by premise 5.

So, it follows that the first member is not potentially this or that, but rather a purely actual reality. While this sounds very distant and abstract, we will defend premise 7 in the next post to show the purely actual reality possesses the attributes of God.


Premise 6 (i.e. There exists a first mover, the first member of the chain, that is pure actuality) follows from premises 4 and 5. In this long post, we did the following:

  • Explained the terminology behind key premises (4) and (5)
  • Defended premises (4) and (5)
  • Showed that the first member must be pure actuality.
  • Pointed out that premise (6) follows from (4) and (5).

In the next post, we defend the idea that a purely actual reality possesses the divine attributes.

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