An Explanation of the Third Way of St. Thomas

Let's begin by defining our terms. First, the word "contingent", from the Latin "com" and "tangere", ('to touch upon'). Contingent means "that which need not be the case", or "something which just happens to be the case". A contingent being is a being that need not be. It is not necessary that the oak tree in your backyard be. It was planted by your grandfather, perhaps, but he need not have planted it. It just happens to be the case that he planted it. You can also purchase an ax and cut it down tomorrow. Hence, it need not be. It came into being at one time, and it can cease to be at one time.

You and I are contingent beings. It is not true to say that "you cannot not be". If that were the case, you'd have always existed. In other words, you and I are not "necessary beings" or non-contingent beings.

Now we'd like to know if there is a non-contingent being that exists. Just defining it does not show that it actually exists. So, we begin by assuming that everything that exists is a contingent being. In the diagram below, the circle represents a contingent being. A contingent being is a composite of essence and existence. It is "what" it is (represented in blue), but it "has" an act of existing (represented in green).

The circles above, then, will represent every contingent thing that had existence, has existence, and will have existence (consider them all in the present). The question is whether we need to posit anything else besides contingent beings..

Now, as was said above, a contingent being has existence. That is, it has an act of existing (esse). This act of existing does not add anything to the nature or essence of the thing. For example, you and I can come to understand the nature of an atelopus exiguus (a type of frog) without knowing whether or not such a thing actually exists. Should the frog be discovered to actually exist, its being will not add anything to the nature of the frog as you understand it already.

And so a contingent being that actually exists is a composite. A composite of what? A composite of "essence" and an "act of existing" (essentia et esse). That is why knowing what a thing is does not tell me whether or not it is, and knowing that a thing is does not tell me what it is. For example, some of those contingent beings represented in the diagram above are presumably entities that we have never encountered before. We can know that something exists on Mars by certain effects, for example, without knowing what it is specifically. In other words, essence and existence are really distinct.

At this point, recall what an analogy is. For example, consider the following analogy: cat is to meow as dog is to ______. The answer, of course, is "bark". Or, 2 is to 4 as 3 is to ______. The answer is clearly "6". Now think of the following analogy: Essence is to existence as potentiality is to actuality.

What this means is that a contingent being is a potential being that has been reduced to an actual being (it has an act of existing). 200 years ago, your oak tree did not exist. Now it actually exists. It has an act of existing. Now, one cannot say that it was impossible for the oak tree to exist. It exists now, in your backyard, which proves that it was possible for it to be. The oak tree is a possibility that has become an actuality. It is a unity of potency and act, or essence and existence. We can know what it is (essence), and we can know that it is (existence). Consider the analogy:

Now the act of existing is an act. The essence is related to the act of existing as potentiality is related to actuality. The atelopus exiguus does not actually exist any more. It is extinct. They were a potentiality to be, and as actually existing beings they were composites of essence and existence. As a composite of essence and existence, this particular frog is now a potentiality not to be (it can cease to be). To prove this, note that the atelopus exiguus is now extinct. They no longer have actual being. So too, your children do not exist. At this point, they are a potentiality to be.

Consider now the diagram above. Everything in the universe that exists is a contingent being. If one does not accept this, but argues that not everything is a contingent being, then the argument becomes much easier. For we are trying to prove just that, namely, that there is a non-contingent being besides contingent beings. So the question at this point is that if everything that is is a contingent being, a possibility made actual, what is it that accounts for the reduction of all these beings from potentiality to actuality? What brings things into being?

There are three possibilities:

  1. A contingent being brings itself into being.
  2. Contingent beings bring contingent beings into being.
  3. A non-contingent being brings things into being.

We can rule out the first two possibilities.

1. A contingent being brings itself into being. This is not possible. If a being does not have an act of existing, then it isn't a being. It is merely a potentiality. But a potentiality without an act of existing does not exist. It is nothing. And nothing brings itself into existence. In order to bring oneself into being, one would have to exist before one exists. But this is absurd. And if a thing does not exist, it cannot do anything.

2. Contingent beings bring contingent beings into being. Contingent beings cannot impart the act of existing. That is, contingent beings cannot reduce a being from potentially existing to actually existing. It is not possible for you or I to bring something into being from nothing. All we can do is bring something into being from already existing material. Even reproduction, for us, is not creation. We do not create our children. We reproduce. We provide our kids with their genetic material, but we don't create them from nothing. We receive them. So, whatever contingent beings do, they must first exist in order to do it, and whatever contingent beings act upon must first exist in order for them to act upon it. Hence, contingent beings do not impart existence.

So it is reasonable to ask: "What accounts for the existence of contingent beings?" Contingent beings do not account for the existence of contingent beings. In other words, contingent beings do not cause existence. Whatever they do, they must first exist in order to do it, and whatever they act upon must first exist in order for them to act upon it. Now a contingent being did not cause itself to be, rather, it was caused to be. Its existence was caused. A contingent being can cause, but it does not impart existence. So as a cause, a contingent being is a caused cause. For example, a carpenter causes the house to be, and so a carpenter is a caused cause. But no contingent being causes being or existence. Hence, only a non-contingent being causes being, that is, only an uncaused cause causes existence. Only a non-contingent being can account for the existence of contingent beings. A non-contingent being is not a possible being, but a being that cannot not be. A non-contingent being is a being whose essence is to be. It is his nature to exist.

In order to have a universe of contingent beings, there must be an uncaused cause. An uncaused cause does not have existence. Rather, an uncaused cause is his own existence. This uncaused cause is what we mean by God, as we will demonstrate in greater detail later. For the uncaused cause is eternal, never came into existence, is the cause of the being of all other beings, and can only be one (as we will show later).

Possible Objections and Replies

Possible Objection:

Reply: This is not quite true. We cannot create or destroy matter. But matter, as the world of science understands it, is contingent. We speak of kinds of matter. The nature of matter is distinct from its existence. This is especially clear when we are dealing with the elements. We can know what a particular element is, and this knowledge does not tell us whether or not that matter actually is. All matter is a composite of essence and existence. If it was not, it could not be multiplied. Its essence would be to exist, and so it would be pure actuality. What is pure actuality, that is, pure act of existing, can only be one, not plural, as we will explain later.

Reply: The very fact that you did not always exist is enough to show that you are not non-contingent, at least absolutely. You are not eternal. You have a received being.

Reply: The non-contingent being does not have a received being. Its nature or essence is to be, whereas your nature is to be human. Its nature is not distinct from its existence. If it were, it would be contingent, and we'd still have the giant question mark hanging over us.

Reply: Even if we suppose that a contingent being always existed, the explaination for its "existence" is not contained in itself, that is, in its nature. Its being is still received. Its essence is still distinct from its existence (otherwise it would be non-contingent). So it would still need an explaination. We could still ask: "What is the cause of its being?".

Reply: The 'him' is just generic. It is appropriate because "him" refers to a principle of a generation (fatherhood), whereas her refers to woman, to whom it belongs to receive and nurture new life in the womb. But since this non-contingent being does not receive existence, but imparts it (as the man imparts his seed, and the woman receives it), it is for the most part appropriate to use "he" instead of "her". Creation is more accurately referred to as her.

Reply: Actually, it isn't the frog's nature to be, otherwise it would still be. It was its nature to be a frog, to croak, swim, etc. What belongs to a thing's nature does so necessarily. For example, if I know that you are human, because someone told me, then I can say that you are necessarily rational, risible, and sentient, etc. But I can't say that you necessarily exist. You might have died a year ago, and it is your brother who is telling me about you. If you do exist, and you are human, you are necessarily rational. Just like a triangle necessarily has three sides. But it isn't necessarily yellow. Yellow does not belong to its nature. And blond hair does not belong to the nature of man, otherwise we'd all be blond, or those of us who are not would not be essentially human. Existence does not belong to our nature, if it did, we'd necessarily be (we'd be non-contingent). So if a thing's nature is to be, then it necessarily is.

Next Page: Chapter 20: Some Implications of God as Ipsum Esse Subsistens
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