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Why God Exists - the 1st way to know!

The First 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…

The Bible teaches in Romans 1:19 – 20 that everyone can know that God is real and what God is like based on what the universe is like. In other words, how the universe works and how things fit together can show why God must be real. In the Middle Ages, a Dominican priest named Thomas Aquinas showed how simple created things in the universe, and how things work all around us, can do this. What he discovered is sometimes called “The Five Ways of Thomas Aquinas.”

Thomas shows in the First Way why nothing can change from being a potential thing or action (such as an idea or a thought) into an actual thing or action unless something that is already real causes the change. For example, think about a crumpled-up piece of paper. In your mind, you can see that the paper has the potential to catch on fire and be turned (or moved) into a pile of ashes. Of course, a normal crumpled-up piece of paper is cool and not burning – and it has the potential to become hot and burning. But it cannot be both burning and not burning at the same time and in the same way so, something must “cause” or “move” the paper from not burning to burning. That seems simple and this obvious truth is called the Law of Cause and Effect. If you see a burning crumpled-up piece of paper (an “effect”) then something or someone must have lit the crumpled-up piece of paper on fire (the “cause” of the fire).

Thomas noticed that whenever things start to happen like this, there is a movement or a motion from what could potentially happen into what actually happens. For example, when a fire begins, it moves from being a potential fire into being a real fire. You can see this in other things also. If a tree falls, it is in motion, but something must put it in motion. If a plant starts to grow, growth is a kind of movement, but something must causes a seed to start growing. All these motions must be caused by someone or something else.

Thomas pointed out that all the movements of everyday things we see in life are the result of a long chain of cause and effect – but this chain cannot go backwards forever. This is true because if this long chain really did go back forever, then there could never have been a first mover in the chain. This is true because every motion that starts must be put in motion by someone or something else. But if there was no first mover, then there could never have been any other movements - and that would mean nothing could have gotten started moving in the first place. This is true because nothing is nothing. Nothing cannot do anything, cannot make anything, or move anything so there must be a beginner - a first mover - a first cause of all other causes and effects. And this first cause cannot be caused by anything or anyone else or it would be part of the chain instead of the foundation. This means that the first mover – must be unmoved Himself. He must be eternal – no start, no end. He must just…exist!

Now, it follows from this that only what already exists can cause something else to go from potential to actual. Another way to think about it would be to picture a pendulum hanging from a long chain. If the links in the chain do not connect with a ceiling, the pendulum cannot hang and cannot move. It does not matter how many links are in this chain, if it does not connect to the ceiling, it will fall.

In the same way, the chain of cause and effect must be connected to a source that does not need anything or anyone to cause it to exist. It must be eternal or else it would need a cause also. Chains cannot hang from nothing – they can only hang from something. The chain of cause and effect that we see in the real world is a real chain that can only be held up by something, or someone who is, Himself, uncaused.


Thomas Aquinas’s First Way is a simple illustration showing why God must exist and why He is eternal and uncaused. This is so because non-eternal things already exist in the real world all around us, and all non-eternal things need a cause. You can remember the “First Way” with the following rhyme: “First - what moves needs a mover to move, so an infinite regress no one can prove.”

Thomas Aquinas wrote,

“Whatever is in motion must be put in motion by another…but this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover…therefore, it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.” [1]

[1] Aquinas, Summa Theologica, 13.

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