5 KEY POINTS
from the article:
from the article:
Imagine that you are an astronomer on a world with one moon. It is always night on your world, and the moon is the only body in the sky. You note that the moon goes through phases — sometimes it is bright and full, sometimes it is dark and new. One night (it’s always night) you are having a conversation with your atheist friend. You raise the question: Where does the moonlight come from? Your atheist friend says “from the moon itself, obviously.” But you point out that the moonlight comes and goes. This implies that there must be something else causing it to come and go. Your atheist friend says, “Moonlight doesn’t need a cause. It just exists.” But you point out that your research through your telescope shows that the moon is a rocky body with mountains and shadows, without any light of its own, and all of its light is reflected. Your atheist friend replies: “Then there must be other moons — moons we can’t see — that are the sources of the reflected light. Its moons, all the way down!” But you point out to your friend that you can’t get light from an infinite regress of mere reflection. If a moon doesn’t make its own light, you can’t provide an ultimate explanation for the light merely by positing the existence of a series of other moons that just reflect light. There must be an ultimate source of the reflected light, something that shines light according to its nature, and doesn’t merely reflect it. There must be a Sun, even though we can’t see it.
The proof of the Third Way proceeds in the same manner. In nature we see things that exist, and can go into and out of existence. Their existence is contingent (their existence is a reflection). But everything that exists can’t exist by contingency. If anything exists at all, there must be Something that necessarily exists — Something that is a source of existence, not a reflection of existence. Contingent existence — reflected existence — can’t go to infinite regress. There must be Something that exists (shines) by its own nature, and gives existence to all other things. The Source of existence must be something for which existence is not merely contingent but necessary.
The universe is contingent — it is a collection of contingent things that can go into and out of existence. Nothing in the universe represents necessary existence — everything in the universe, as well as the entire universe itself, is capable on not existing. That is, we can describe the universe (its essence) without affirmation of its existence. In fact, existence of the universe is finite — it began with the Big Bang and will end with (presumably) the Big Crunch.
The universe contains things that are capable of beginning to exist and of ceasing to exist.
Things in the universe do in fact begin to exist and cease to exist.
This represents elevation of potency (potential existence) to act (actual existence).
By the law of non-contradiction, potency and act cannot coexist in a thing in the same respect.
Therefore, the universe cannot cause itself to exist.
The universe does exist, therefore its cause of existence must be Something Whose existence is necessary and not contingent.
That is what all men call God.
Existence of contingent nature cannot go to infinite regress, just as moons reflecting light cannot go to infinite regress. There must be a Sun. The existence we see all around us is merely reflected existence, and it points in a remarkably direct way to the Source of existence. The existence of nature presupposes a Necessary Existence that is outside nature that provides the existence reflected in natural things. This is what all men call God.
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evolutionnews.org/2019/10/aquinas-third-way-and-the-moonlight
evolutionnews.org/2019/10/aquinas-third-way-and-the-moonlight