The Two Kinds of Causal Demonstration

The Two Kinds of Causal Demonstration 

Matthew Bellisario O.P. 2020

I am currently reading Saint Thomas' Summa Contra Gentiles. I recently purchased the Aquinas Institute's beautiful publication as well as Brian Davies' guide and commentary on the work. I find that reading the Summa along with Davies' commentary is helping me to better digest the work making my study more fruitful. If you are planning on reading the Summa I highly recommend you purchase Davie's work to go along with it. 

"The human understanding cannot go so far of its natural power as to grasp His substance, since under the conditions of the present life the knowledge of our understanding commences with sense; and therefore objects beyond sense cannot be grasped by human understanding except so far as knowledge is gathered of them through the senses. But things of sense cannot lead our understanding to read in them the essence of the Divine Substance, inasmuch as they are effects inadequate to the power that caused them. Nevertheless our understanding is thereby led to some knowledge of God, namely, of His existence and of other attributes that must necessarily be attributed to the First Cause. There are, therefore, some points of intelligibility in God, accessible to human reason, and other points that altogether transcend the power of human reason." Summa Contra Gentiles Chapter 3

The beginning of the Summa Contra Gentiles deals at great length with arguments for knowing the existence of God. There are two ways of knowing about God, the first through natural reason and the second through His Divine Revelation. This post concerns the use of natural reason. Although man through natural reason alone can come to know the existence of God, (Defined at Vatican I) it is rather difficult for many people to arrive at this conclusion due to several difficulties. The first of these difficulties being the consequences of original sin which makes it harder for us to perceive truth because of our weakened intellect. Aquinas also says that it requires assiduous study and effort which many cannot do for a variety of reasons. (Chapter 4)

Beginning with the basics Aquinas argues for a particular manner of examining causality in order to arrive at knowledge for the existence of God. Being that most Catholics today are ignorant of basic Thomistic philosophical principles and logical reasoning, Davies explains the two ways in which Aquinas demonstrates causality. One is from the top-down and the other from the bottom-up. Understanding these two methods goes a long way in understanding how to properly reason and examine the world around us. Although we all use these methods we really do not think about them with any specificity. 

In his guide, Davies writes, "Aquinas recognizes two kinds of causal demonstration: (1) from cause to effect, and (2) from effect to cause." Traditionally these two methods were referred to by theologians by their Latin terms as proper quid (of the reason for, from cause to effect) and the second being quia (That, from effect to cause) In general we can use both of these methods to examine things in relation to others so we can learn what their teleology is, what their nature and essence are and so forth. There is a problem however with using the first method in our natural reasoning for God's existence. 

Davies uses the following example in demonstrating the two causes. 

 Demonstration from cause to effect.

1. Hydrogen is the element with atomic number one.

2. The element with atomic number one is the lightest gas.

3. So hydrogen is the lightest gas. 

4. Any balloon filled with the lightest gas rises in air.

5. So any balloon filled with hydrogen rises in air. 

 Demonstration from effect to cause.

1. This balloon is rising in the air.

2. Every rising balloon is full of something that makes it rise.

3. So this balloon is full of something that makes it rise.

4. Everything that fills a balloon and makes it rise must be lighter than air.

5. So this balloon is full of something lighter than air. 

In order to argue from the top-down as it were, we must have some knowledge of the thing as we perceive it through our senses. We must be able to know something about it through some type of investigation of the object itself. Even though we cannot see hydrogen, we can perform experiments with hydrogen and prove its existence by certain truths about it. We can measure its components and define its characteristics. It is observable as a thing. The problem we have with God is that we cannot examine God through our senses or perform any type of experimentation in a lab to find out about the nature or essence of God. Unless we are given Divine Revelation or some miraculous infused knowledge of God that is not ordinarily known through the senses there is no possible way to use method one and we would no longer be using natural reason alone with this knowledge. The point is, we do not know the nature or essence of God from natural reason the way we can concerning hydrogen. If God does exist, however, this is not really surprising since God would transcend every visible essence by virtue of what God is not. This means that coming from natural reason alone, we must reason from the bottom-up as it were and look at the effects which we can perceive through the senses to get an idea of the existence of God. 

When we observe creation itself we can deduce by the way things work in nature that there must be an ultimate cause, although we are very limited to what we can know about God. For example, we cannot know about the Trinity or of Jesus's incarnation by natural reason which is why God gave us His Divine Revelation. Some theologians especially in Protestant circles have criticized those who try to demonstrate God's existence through natural reason, yet even Scripture attests to this possibility. Romans 1:20-21 offers us insight, "For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made. His eternal power also and divinity: so that they are inexcusable. 21 Because that, when they knew God, they have not glorified him as God or given thanks: but became vain in their thoughts. And their foolish heart was darkened." Although our intellect is weakened its faculties are not totally destroyed. 

Aquinas argues then that God is not self-evident in the way that sensible things are which can be measured by some material means from the top-down. He says, "Absolutely indeed the existence of God is self-evident, since God's essence is His existence. But since we cannot mentally conceive God's essence, his existence is not self-evident relatively to us." (Chapter 11) Using natural reason alone man can only use the second method by looking at the effects first rather than the cause to know God exists. Hence Aquinas says, "...because we cannot see His essence, we are brought to the knowledge of His existence, not by what He is in Himself but by the effects which He works." (Chapter 11)

This brief examination of Aquinas' Summa Contra Gentiles is an excellent way to understand the two kinds of causal demonstration. I think that understanding this is important for us so we can better articulate our faith in general. I hope to share more insight that I find from my reading and study of Thomas's Summa Contra Gentiles and Davies' book as I make my way through them.