Aquinas' Second Proof of God: The Argument from Causation

Thomas Aquinas, one of history’s greatest thinkers, didn’t just rely on faith to explain the existence of God—he used logic and reason. His second argument for God’s existence is called the Argument from Causation. It’s a way of asking, "Why is there something instead of nothing?" Let’s explore this in straightforward terms with relatable examples and analogies.

The Big Idea: Everything Has a Cause

Look at the world around you. Every event, object, or change has a cause. For example:

• A cake exists because someone baked it.
• A building stands because workers constructed it.
• A car drives because an engine powers it.

Nothing in the world just "pops" into existence out of nowhere. Everything depends on something else to bring it into being.

The Chain of Causes

Here’s where things get interesting. Let’s say you’re enjoying a slice of that cake. The cake was caused by the baker, who used ingredients, an oven, and their time to create it. But where did the ingredients come from? Maybe the flour came from wheat, which grew because of soil, sunlight, and water. And where did the soil, sunlight, and water come from? If we keep asking "What caused this?" we end up in a long chain of causes and effects.

Now imagine tracing this chain back further and further. If everything is caused by something else, does that mean the chain goes back forever? Aquinas says no—an infinite chain doesn’t solve the puzzle. There must be a first cause, something that started everything but wasn’t caused by anything else. Aquinas argues that this uncaused cause is what we call God.

An Analogy: A Line of Falling Dominoes

Picture a line of dominoes standing upright. You tap the first domino, and the rest fall in sequence. Each domino’s fall is caused by the one before it. But if there’s no first domino to start the chain, none of them would fall. The first domino is like God—the uncaused cause that gets everything started.

A Real-World Example: Your Family Tree

Think about your family tree. You exist because of your parents, and they exist because of their parents, and so on. If you keep going back in time, where does it all begin? There has to be a first ancestor, a beginning to the chain of life. For Aquinas, the ultimate beginning of everything is God.

A Clue from Science: The Big Bang

Scientists tell us the universe had a beginning, often described as the Big Bang. But what caused the Big Bang? Science can describe how the universe expanded from a single point, but it doesn’t explain why it happened. Aquinas’s argument suggests that the ultimate cause—the one that started it all—is God.

Conclusion

The Argument from Causation asks us to think about why anything exists at all. Everything in our world depends on something else, but the chain of causes can’t go back forever. There must be an uncaused cause that started everything. For Aquinas, this is God—the source of all existence and the reason there is something rather than nothing.

By using examples from everyday life, like dominoes and family trees, we can see how Aquinas’s argument makes sense. It’s a logical way to think about the universe and its ultimate cause.

References

• Aquinas, Thomas. Summa Theologica. Translated by Fathers of the English Dominican Province. Benziger Bros., 1947. Available online at: New Advent.
• Feser, Edward. Five Proofs of the Existence of God. Ignatius Press, 2017.
• Craig, William Lane. Reasonable Faith: Christian Truth and Apologetics. Crossway, 2008.
• Hawking, Stephen, and Mlodinow, Leonard. The Grand Design. Bantam Books, 2010.