This is the fifth installment in a series of articles demonstrating the reasonableness of the claims of the Catholic Church. Part I here; Part II here; Part III here; and Part IV here.

(LifeSiteNews) — In the previous installment we demonstrated that the existence of God can be known with certainty from what we observe of “motion,” or change, in the world around us.

In this article we will explore a second path by which we can attain certainty about the existence of God: the argument from “efficient causality.”

The distinction between the ‘first way’ and the ‘second way’

The similarities between these two proofs can often leave readers confused as to the precise nature of the difference between them.

St. Thomas explains the distinction as follows:

The first and more manifest way is the argument from motion.^[1]

And:

The second way is from the nature of the efficient cause.

As we noted in the previous article, St. Thomas’s proofs for the existence of God all begin with something which we can easily observe in the world around us.

The “first way” begins with our sensory perception that the things of our experience are subject to change. When a craftsman carves a domino out of wood, we can observe the motion of his hand, and the changes that take place in the wood.

The “second way” begins with our perception that the things in the world around us have been caused by something other than themselves. When a craftsman carves a domino out of wood, we observe that the craftsman is the cause of the domino.

There is a distinction between the observation of motion and the observation of efficient causality, and thus the proofs proceed from a different point, even though there is a similarity in how they develop.^[2]

But what is “efficient causality”?

Efficient causality

The “second way” will not be too difficult to understand once we understand the meaning of the term efficient causality.

First, let’s see what we mean by cause and effect.

• A cause is anything which contributes in any way to the producing of a thing.   
• An effect is the thing produced by the causes.

The relationship between cause and effect is called causality.

There are countless different causes in the observable universe. However, they can all be categorized as either intrinsic or extrinsic.

• Intrinsic causes are “in the thing,” they are part of it, and they cannot be separated from it. For example, the wood of which a domino is made. 
• Extrinsic causes are external to the thing. For example, the craftsman who carved the domino.

Intrinsic causes can be further subdivided into material and formal causes:

• The material cause is the matter of which a thing consists. For example, the wood marble, or gold of which a particular statue is made. 
• The formal cause is that which constitutes a thing as precisely the thing that it is. It is that which determines and specifies the matter. For example, a marble statue of a particular size, shape, weight, and so on.^[3]

Extrinsic causes can be subdivided into efficient and final causes:

• The efficient cause is that which produces an effect by its own action. For example, the sculptor is the efficient cause of the marble statue. The efficient cause may have its effect through an instrumental cause, which in this case might be the chisel and hammer with which the sculptor works.
• The final cause is that towards which the efficient cause is directed in the production of the effect. In this example, the sculptor may wish to make a statue of Our Lady so as to move men to prayer. Of course, things need not be consciously aware of their final causes; the wooden torch does not intend to burn and give light, but the nature of the wood does dispose it towards the end of burning.

All causes fall under one these four categories: material causes, formal causes, efficient causes, and final causes. For the rest of this article, we will be concerned only with the nature of the efficient cause.

How we can demonstrate the existence of God from the nature of the efficient cause

When we observe the world around us, we see that everything of which we have experience is the product of an efficient cause. The wooden desk at which I am working was made by a carpenter. The desk is the effect, and the carpenter is the efficient cause. I am sitting at the desk typing and I am the efficient cause of the words appearing of my computer screen, the keyboard, and other parts of the computer’s hardware and software being instrumental causes. The screen was made by a computer manufacturer, an efficient cause, using machinery, that is, instrumental causes.

When we consider the multi-stage process by which a computer is manufactured, we will easily realize that there must be a whole sequence of efficient causes producing their own effects prior to a complete and working computer arriving on my desk. Such patterns of causation are observable all around us.

It is with this undeniable fact that St. Thomas begins the “second way”:

In the world of sense we find there is an order of efficient causes.

Now, neither the computer, nor the manufacturer, nor the machinery, could bring themselves into existence. And when we observe the world around us, we will see that this is true of everything of which we have experience:

There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible.

A thing may be an efficient cause of something else, but nothing of which we have experience is its own efficient cause. No man ever produced himself and no machine ever produced itself, and nor does anything else in the observable universe.

An infinite series of efficient causes is impossible

The conclusion above is one we must draw from the data provided by our senses, data which is certainly reliable, as we saw in a previous article.

However, this conclusion leaves us with a difficulty, which requires further reasoning to resolve.

The difficulty is that if everything is the product of an efficient cause, then nothing can act as an efficient cause of any other thing, until it has itself been produced by an efficient cause.

But if everything must be produced by another thing before it can produce any other things, how was any effect ever produced?

A common way to attempt to evade this problem is to push the problem further and further back in time. But the problem of efficient causality doesn’t go away just because you push the chain of causality back billions of years.

To see this more clearly, let’s imagine a particular man (let’s call him Tom) who has a son. Tom is the efficient cause of his son’s existence, his son is the efficient cause of the existence of his grandchildren, his grandchildren are the efficient cause of the existence of his great-grandchildren, and so on, for all future generations. The existence of each generation is dependent on every generation in the chain. If Tom hadn’t existed then, his great-grandchildren wouldn’t exist now.

It is important to note further that while Tom can be an efficient cause in a chain of causation for all future generations of his family, he cannot be the cause of his own existence, nor of his parents, nor any of his ancestors. Tom only exists because of a previous sequence of efficient causes. He is as dependent on the existence of those efficient causes as his descendants are on his existence.

Further, we know Tom’s parents, and grandparents, and great-grandparents were also efficient causes and the products of efficient causes. We know that as human beings they could not have produced themselves but must have been produced by an efficient cause of the same nature.

Therefore, while we can entertain the idea that Tom’s line of descent may go forward in time indefinitely, we can’t trace the line of his ancestors back to infinity. That is, we cannot find a human ancestor who could have produced himself.

And evolution would not solve this. It would simply leave us with a longer sequence of efficient causes, none of which would have been able to produce itself. And what is true of human beings, or other living beings, is true of all the things of which we have sensory experience, without exception.

Therefore, St. Thomas writes:

Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one.

The first cause in a sequence must exist, because, as we have seen, the existence of the later causes is dependent on it. Each intermediate cause is subordinated to the preceding cause. If Tom hadn’t existed, neither would his grandchildren. If Tom’s first ancestor hadn’t existed, neither would Tom. To take either of these men away, is to take away all their descendants.

As St. Thomas says:

Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause.

But we have seen that there can be no first efficient cause, which is of such a nature as to itself be the effect of another cause. That is, a produced thing, like a human being or a machine, cannot be its own efficient cause. 

Therefore, to account for the universe that we observe with our senses, we must posit the existence of a first efficient cause, which is of such a nature as to be itself uncaused. There must be an uncaused cause. 

If such a being did not exist, we would be unable to account for a universe which consists of beings that cannot be their own efficient causes.  

And therefore St. Thomas Aquinas concludes: 

But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God. 

The being that is the First Efficient Cause is the principal cause of all the effects in the universe. It is the origin of all existence and all change. The being that is the Uncaused Cause necessarily has no origin and must therefore be eternal.  

This eternal being which causes all the other things that exist, is truly the being that is signified by the word “God.”