In Thomistic philosophy, rooted in the teachings of St. Thomas Aquinas, the assertion that God does not require a cause is central. This idea stems from the concept of God as a necessary being—one whose existence is self-sustained and not dependent on anything else. To make this concept clearer, we’ll explore Aquinas’s reasoning, address challenges to his view, and provide simple analogies and rebuttals to these objections.

Understanding Necessary vs. Contingent Beings

Aquinas distinguishes between two types of beings: necessary and contingent. Contingent beings, like humans, animals, and plants, have a beginning and an end. Their existence depends on external factors. For example, a tree exists because a seed was planted and had access to sunlight, water, and nutrients. Without these conditions, the tree wouldn’t exist.

On the other hand, a necessary being is one that must exist by its very nature; it doesn’t rely on anything else for its existence. In Thomistic thought, God is this necessary being.

The Concept of the Unmoved Mover

Aquinas introduces the "Unmoved Mover" to explain motion and change in the universe. Everything in motion is set in motion by something else. However, this chain cannot regress infinitely; there must be a first cause that is not moved by anything else. This "Unmoved Mover" is what Aquinas identifies as God (Summa Theologica, I, Q.2, Art.3).

Analogy: The Domino Effect

Imagine a line of dominoes. Each domino’s fall is caused by the one before it, but the sequence starts only when an external force—like a hand—tips the first domino. In this analogy, the hand represents the "Unmoved Mover," setting everything into motion without being moved itself.

Challenges to Aquinas’s View

While Aquinas’s arguments are influential, they’ve faced criticism over the centuries. Let’s explore some common challenges and Aquinas-inspired responses.

Challenge 1: If Everything Needs a Cause, Why Not God?

Critics often ask, “If everything needs a cause, why should God be an exception?” This question seems to undermine the logic of Aquinas’s argument.

Rebuttal: Misunderstanding the Premise

Aquinas never claimed that everything needs a cause. He argued that contingent beings—those that don’t exist necessarily—require causes. However, a necessary being, like God, exists by its very nature. God is the exception because God's existence is not contingent but intrinsic, like the sun shining light by its nature.

Challenge 2: Why Can’t the Universe Be the Necessary Being?

Some argue that the universe itself could be the necessary being, existing eternally without a cause.

Rebuttal: The Universe is Contingent

Aquinas would respond that the universe shows signs of contingency. For example, stars are born and die, galaxies form and dissipate, and physical laws could theoretically be different. These are marks of a system that is not self-sustaining but reliant on external factors. A necessary being, by contrast, must exist without dependence on anything else.

Analogy: A Book That Needs a Reader

Imagine a book that only exists while someone is reading it. The universe, Aquinas argues, is like that—it requires something (God) to sustain it.

Challenge 3: Why Can’t There Be an Infinite Chain of Causes?

Another objection is that there could be an infinite regression of causes—an endless chain of things causing one another, without needing a first cause.

Rebuttal: Infinite Regress Doesn’t Explain Existence

Aquinas would argue that an infinite chain doesn’t explain why anything exists in the first place. Imagine an infinite row of dominoes. If no one tips the first one, no domino will fall, no matter how many there are. Similarly, without a first cause, the entire chain of existence would collapse.

Challenge 4: How Do We Know the Unmoved Mover is God?

Even if we accept the need for an Unmoved Mover, critics ask why we should identify this being with the God of classical theism.

Rebuttal: Properties of the Necessary Being

Aquinas argues that the characteristics of the Unmoved Mover align with what we mean by God: eternal, unchanging, all-powerful, and self-sufficient. For example, if the Unmoved Mover is the cause of all existence, it must itself contain no potential for change—qualities attributed to God.

Conclusion

In Thomistic philosophy, God is understood as the necessary being, the Unmoved Mover, and pure actuality. These concepts illustrate why God doesn’t need a cause: God’s existence is self-sustained, unchanging, and not dependent on anything else. While challenges to this view exist, Aquinas’s reasoning and analogies like the domino effect help to defend his position. For those willing to explore further, these ideas open the door to deep reflections on existence and the nature of reality.

References

Aquinas, T. (n.d.). Summa Theologica. Retrieved from New Advent.

Feser, E. (2017). Five Proofs of the Existence of God. San Francisco: Ignatius Press.

Kreeft, P. (1990). A Summa of the Summa. San Francisco: Ignatius Press.