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Why God exists - the 2nd Way to know!

Updated: Jul 12, 2021

The Second Way we can know that God is real!

© 2021 Patrick C. Marks, All rights reserved

The following is a preview from the FAQ section of my new book…

Romans 1:19 – 20 says that how the universe works and how things fit together show everyone why God must exist, so people are without an excuse for not believing God is real. In the Middle Ages, Thomas Aquinas showed five simple ways about how things exist and work in the universe that show why God must be real. His “Second Way” to show this is sometimes called “the Way of the First Cause.”

The “First Way” explained that the law of cause and effect cannot go back forever because then the chain of cause and effect would be grounded in nothing. This is so because nothing cannot do or make anything, so there must be an eternal “something” or “someone” that caused everything else. But many people ask, “if everything needs a cause, then who caused God? Why should God be the exception to the law of cause and effect?”

To answer this, Aquinas points out that not everything needs a cause. Only what begins to exist needs a cause. This is true because what begins to exist is made by something that already exists. For example, you began to exist when the cells from your father and mother joined together – but the material in your father and mother’s cells, and all the nutrients you took in as a new, growing baby, were things that existed before you did. This means you, and every other living being, is a “dependent” (or contingent) being. You are dependent for the start of your existence upon things already existed (cells, nutrients, water etc) before you started to exist.

Not only that, but you continue to exist right now, in the present, because all the nutrients, water and so on that you need to be alive, each and every day, is stuff that already exists. You are not just dependent on those things to begin to exist, but you are also dependent on those things to keep on existing – if these other things did not exist, or stopped existing, then you would stop existing also. Imagine if water suddenly stopped existing. If that happened, you would stop existing. But water is a dependent thing also. Water is made up of hydrogen and oxygen atoms, so the existence of water depends on the existence of hydrogen and oxygen atoms. Thus, every minute of every day, everything around us depends on pre-existing things in order to keep on existing.

But if everything that begins to exist is dependent, where did everything come from? This is another chain that cannot go back forever. If everything is dependent, then everything must depend on something. There must be a starting point, something that gives existence to everything else, but this starting point must also keep everything existing at every moment.

That means the starting point itself cannot depend on anything else or it would not be the starting point. And it also cannot be something that causes itself to exist either. For example, you cannot be self-caused because then, in order to cause your own existence, you would have to exist before you started to exist in order to create yourself – and that is impossible. So, there must be something or someone that has always existed and does not owe existence to anything or anyone else.

Another way to think about it is to imagine a long chain suspending a lamp over a table. The lamp will not stay hanging up over the table unless the chain that holds it up is connected to the ceiling. This is like the cause-and-effect chain Aquinas talked about in the First Way. But Aquinas is also saying that each link in the chain is dependent on the link before it and after it in order to be a part of the chain at all. So, each link is dependent on something before it or else it could not exist right now as part of the chain.

What this means is there must be something that causes the whole chain to exist at every moment, something that is not dependent on anything else. Philosophers call this need the “uncaused cause” or “the Being that exists necessarily.” So, because we can see things in the universe today that are dependent, that is, things which began to exist, then there must be something or someone that is independent. There must be something or someone who has always existed.

The Bible teaches us that God has always existed. It says in Psalm 90:2, “Before the mountains were born, Or You gave birth to the earth and the world, Even from everlasting to everlasting, You are God.” God, as the everlasting, uncreated Being is exactly the description of what is needed to explain the dependent things we see in the universe today. God makes it possible for everything to keep existing, moment by moment.

The Bible also tells us God has the power within His own Being to make everything else. Jeremiah 32:17 says, “Behold, You have made the heavens and the earth by Your great power and by Your outstretched arm! Nothing is too difficult for You…” Again, this is a description of a Being that is uncaused but can cause everything else. It fits what is needed to explain the great chain of cause and effect.


An easy way to remember The Second Way is this: “Aquinas’s second way says you can’t exist before yourself, so God must have existed forever by Himself.” The Second Way is about “efficient cause.” For example, you do not cause your own existence (moment by moment) and you did not exist before you existed in order to create yourself either, so you are dependent on something else to begin existing and keep on existing. Since an efficient cause must be something that causes the existence of something else (or causes a change in something else), this chain cannot go backwards forever. If it did, there would be no first efficient cause. If there was no first efficient cause of everything, which makes everything able to keep existing right now, then nothing at all would exist right now. This means there must be a first efficient cause of everything – something that holds everything else up. The uncaused, first efficient cause of all other causes is what we call God. The Bible tells us God is everlasting and that He has power in Himself to cause everything else to exist.

Thomas Aquinas’s wrote,

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….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. [1]

[1] Aquinas, Summa Theologica, 13.

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