The God Debate: Aquinas to Mackie

The debate over the existence of God is one of the oldest and most significant discussions in human history. For centuries, philosophers, theologians, scientists, and everyday people have grappled with the question: Does God exist? The implications of this question touch on the nature of reality, morality, and the purpose of life itself. Some argue that the complexity of the universe and the existence of moral order suggest a divine creator, while others point to the presence of evil and the lack of empirical evidence as reasons to reject the idea of God. For related topics, see our articles on modes of thought and meditation and meaning.

In this article, we will examine the strongest arguments for and against the existence of God, presenting multiple perspectives and attempting to draw a comprehensive conclusion based on these competing viewpoints.

Highlights

• Thomas Aquinas's Five Ways (1265-1274): Dominican friar (1225-1274) formulated Quinque viæ in Summa Theologica to demonstrate God's existence; arguments from motion (unmoved mover), causation (uncaused cause), contingency (necessary being), degrees of perfection, and teleology; first three considered types of cosmological argument
• William Paley's watchmaker analogy (1802): English clergyman (1743-1805) published Natural Theology arguing watch's complexity demands intelligent designer; similarly, universe and living organisms far more complex than watch, thus must have divine creator; book went through 10 editions in first 4 years; significantly influenced Charles Darwin before he developed natural selection
• C.S. Lewis's moral argument (1952): Mere Christianity presented journey from atheism; argued awareness of moral values points to transcendent standard of good; "If whole universe has no meaning, we should never have found out"; atheism "turns out to be too simple"
• J.L. Mackie's "Evil and Omnipotence" (1955): Published in Mind (volume 64, pages 200-212); one of most forceful articulations of Logical Problem of Evil; argued belief in all-powerful, all-knowing, all-good God is "positively irrational" when evil exists; claimed three propositions contain contradiction; even Mackie later admitted Plantinga's free-will defense solved problem if understood as logical inconsistency
• Pascal's Wager (1657-58): French mathematician Blaise Pascal (1623-1662) applied game theory to show belief in God is rational; found in §233 of Pensées; published posthumously 1670; if God doesn't exist, believer incurs only finite losses; if God exists, believer gains immeasurably (eternal Heaven) while avoiding boundless losses (eternal Hell)
• Francis Collins: Human Genome Project director sees no conflict: Argues scientific discovery can lead to deeper understanding of God's creation; Einstein: "Science without religion is lame, religion without science is blind"

Arguments for the Existence of God

The Cosmological Argument

One of the most well-known arguments for the existence of God is the Cosmological Argument. This argument posits that everything that exists must have a cause, and since the universe exists, it too must have a cause. Proponents argue that the "First Cause" of the universe must be God, an eternal and uncaused being who set everything in motion.

This idea can be traced back to philosophers such as Thomas Aquinas (1225-1274), who famously formulated the Five Ways (Quinque viæ) to demonstrate the existence of God in his Summa Theologica, written between 1265 and 1274. One of these ways was the argument from motion, which claims that since everything in motion must have been set in motion by something else, there must be an initial unmoved mover—God. Aquinas's first three arguments—from motion, from causation, and from contingency—are considered types of the cosmological argument.

Modern cosmology also lends some support to this argument. The Big Bang theory, which suggests that the universe had a beginning, aligns with the idea that something (or someone) must have caused the universe to come into existence. The existence of a finite universe points to the need for a transcendent cause beyond space and time.

The Teleological Argument (Design Argument)

Another key argument for the existence of God is the Teleological Argument, also known as the Design Argument. This argument suggests that the complexity, order, and fine-tuning of the universe imply the existence of an intelligent designer. Proponents of this argument point to examples like the precise conditions necessary for life on Earth, such as the specific force of gravity or the exact distance of the Earth from the sun.

William Paley (1743-1805) famously illustrated this argument with his watchmaker analogy in his 1802 work Natural Theology, or Evidences of the Existence and Attributes of the Deity. Paley argued that if you discovered a watch upon the ground, unlike a stone, the watch's complexity would demand explanation by an intelligent designer. Similarly, Paley argued, the universe and living organisms are far more complex than a watch and thus must have been designed by a divine creator. The book was very successful, going through ten editions in the first four years alone, and significantly influenced Charles Darwin before he developed natural selection.

In modern times, the idea of fine-tuning—the precise conditions necessary for the existence of life—has been used to bolster the teleological argument. Some scientists and philosophers, such as Stephen Meyer, have argued that the improbability of life arising by chance suggests that the universe was designed with life in mind.

The Moral Argument

The Moral Argument contends that the existence of objective moral values and duties is best explained by the existence of God. This argument hinges on the idea that if moral values like good and evil, right and wrong, exist independently of human opinion, there must be a higher moral lawgiver—God.

Philosophers like Immanuel Kant and C.S. Lewis have argued that without God, morality becomes subjective and relative, depending on individual or cultural preferences. The existence of universally recognized moral principles, such as the wrongness of murder or the goodness of helping others, suggests a divine source of moral law.

In his 1952 book Mere Christianity, Lewis famously stated, "If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark." This follows Lewis's discussion of his own journey from atheism, where he explains that in trying to prove God did not exist, he found himself assuming that his idea of justice was full of sense, concluding that "atheism turns out to be too simple." The very awareness of moral values, he argued, points to a transcendent standard of good that originates with God.

Arguments Against the Existence of God

The Problem of Evil

One of the most compelling arguments against the existence of God is the Problem of Evil. This argument questions how an all-powerful, all-good God could allow the existence of suffering and evil in the world. If God is omnipotent, He should be able to prevent evil; if He is omnibenevolent, He should want to prevent evil. Yet, evil and suffering exist, leading some to conclude that God does not.

Philosophers like Epicurus and David Hume have posed this challenge, known as the logical problem of evil. Hume famously asked, "Is [God] willing to prevent evil, but not able? Then he is impotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Whence then is evil?"

While some theists have responded by arguing that evil is necessary for free will or that suffering can lead to greater goods, the problem of evil remains a significant obstacle to belief in an all-powerful, benevolent deity.

The Argument from Incoherence

Another argument against the existence of God is the Argument from Incoherence, which claims that the concept of God contains logical contradictions. For example, how can God be both omniscient and omnipotent? If God knows everything, including the future, then He cannot change the future, which would imply a limitation on His power. Alternatively, if God can change the future, He cannot be said to know it with certainty.

Philosophers like J.L. Mackie have pointed out these contradictions, most notably in his 1955 article "Evil and Omnipotence" published in Mind (volume 64, pages 200-212), which is considered one of the most forceful articulations of the Logical Problem of Evil. Mackie argued that belief in an all-powerful, all-knowing, and all-good God is "positively irrational" when evil exists, claiming these three propositions contain a contradiction. He questioned why God could not have made humans such that they always freely choose good. The traditional concept of God as described in classical theism, Mackie argued, is logically incoherent. (Note: Philosopher Alvin Plantinga later developed a free-will defense that even Mackie admitted solved the problem if understood as one of logical inconsistency.)

The Evidential Problem of Divine Hiddenness

The Evidential Problem of Divine Hiddenness asks why, if God exists, there is insufficient evidence for His presence. If God desires for humans to know and worship Him, why does He remain hidden from so many? This argument asserts that the lack of clear, empirical evidence for God's existence—especially in a world where belief in God would be so beneficial—casts doubt on theism.

J.L. Schellenberg is a key proponent of this argument, suggesting that God's hiddenness is incompatible with the idea of a loving deity who wants humans to have a relationship with Him. If a loving God exists, wouldn't He provide more evidence of His existence, especially for those who are genuinely open to belief?

Agnosticism and the Middle Ground

For many, neither the arguments for nor against the existence of God are entirely convincing. This has led to the rise of agnosticism, the view that the existence of God is unknown or unknowable. Agnostics argue that human beings may not have the cognitive capacity to answer such profound questions, and thus, it is best to withhold judgment on the matter.

One famous argument related to the God question is Pascal's Wager, found in §233 of the Pensées (1657-58) by French mathematician and philosopher Blaise Pascal (1623-1662). Pascal's notes were published posthumously in 1670. Pascal applied elements of game theory to show that belief in God is rational. He argued that individuals engage in a life-defining gamble regarding belief: if God does not exist, the believer incurs only finite losses (certain pleasures and luxuries); if God does exist, the believer stands to gain immeasurably (eternal Heaven) while avoiding boundless losses (eternal Hell). Pascal suggested that a rational person should adopt a lifestyle consistent with God's existence and strive to believe in God.

Agnosticism offers a middle ground for those who find both theism and atheism lacking in definitive proof.

Can Science and Religion Coexist?

Another important aspect of the God debate is the relationship between science and religion. Some argue that science and religion are in conflict, with scientific inquiry undermining the need for belief in God. Others, however, maintain that science and religion address different questions: science explains how the universe works, while religion addresses why it exists.

Albert Einstein once said, "Science without religion is lame, religion without science is blind," suggesting that the two fields can complement one another. Scientists like Francis Collins, the director of the Human Genome Project, have argued that scientific discovery can lead to a deeper understanding of God's creation.

Frequently Asked Questions

What is the cosmological argument for God's existence?

The cosmological argument posits that everything that exists must have a cause, and since the universe exists, it too must have a cause. This "First Cause" must be God, an eternal and uncaused being who set everything in motion. Thomas Aquinas (1225-1274) famously formulated the Five Ways (Quinque viæ) in his Summa Theologica (written 1265-1274) to demonstrate God's existence. His first three arguments—from motion, causation, and contingency—are considered types of the cosmological argument. The argument from motion claims that since everything in motion must have been set in motion by something else, there must be an initial unmoved mover—God. Modern cosmology lends some support: the Big Bang theory suggests the universe had a beginning, aligning with the idea that something (or someone) must have caused the universe to come into existence.

What is Paley's watchmaker argument?

William Paley (1743-1805), an English clergyman, illustrated the teleological (design) argument with his famous watchmaker analogy in his 1802 work Natural Theology, or Evidences of the Existence and Attributes of the Deity. Paley argued that if you discovered a watch upon the ground, unlike a stone, the watch's complexity would demand explanation by an intelligent designer. Similarly, Paley argued, the universe and living organisms are far more complex than a watch and thus must have been designed by a divine creator. The book was very successful, going through 10 editions in the first 4 years alone, and significantly influenced Charles Darwin before he developed his theory of natural selection. Modern proponents point to "fine-tuning"—the precise conditions necessary for life—suggesting the universe was designed with life in mind.

What is the problem of evil?

The Problem of Evil questions how an all-powerful, all-good God could allow the existence of suffering and evil in the world. If God is omnipotent, He should be able to prevent evil; if He is omnibenevolent, He should want to prevent evil. Yet evil and suffering exist, leading some to conclude that God does not exist. Philosopher David Hume famously asked: "Is [God] willing to prevent evil, but not able? Then he is impotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Whence then is evil?" J.L. Mackie's 1955 article "Evil and Omnipotence" (published in Mind, volume 64, pages 200-212) is considered one of the most forceful articulations, arguing that belief in an all-powerful, all-knowing, all-good God is "positively irrational" when evil exists. However, even Mackie later admitted that Alvin Plantinga's free-will defense solved the problem if understood as one of logical inconsistency.

What is Pascal's Wager?

Pascal's Wager is found in §233 of the Pensées (1657-58) by French mathematician and philosopher Blaise Pascal (1623-1662), published posthumously in 1670. Pascal applied elements of game theory to show that belief in God is rational. He argued that individuals engage in a life-defining gamble regarding belief: if God does not exist, the believer incurs only finite losses (certain pleasures and luxuries); if God does exist, the believer stands to gain immeasurably (eternal Heaven) while avoiding boundless losses (eternal Hell). Pascal suggested that a rational person should adopt a lifestyle consistent with God's existence and strive to believe in God. This pragmatic approach to belief doesn't prove God exists but argues that believing is the rational bet regardless of certainty.

What was C.S. Lewis's moral argument?

In his 1952 book Mere Christianity, C.S. Lewis presented a moral argument for God's existence based on his own journey from atheism. Lewis argued that the existence of universally recognized moral principles—such as the wrongness of murder or the goodness of helping others—suggests a divine source of moral law. He famously stated: "If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark." Lewis explained that in trying to prove God did not exist, he found himself assuming that his idea of justice was full of sense, concluding that "atheism turns out to be too simple." The very awareness of moral values, he argued, points to a transcendent standard of good that originates with God.

Can science and religion coexist?

Many thinkers argue that science and religion address different questions: science explains how the universe works, while religion addresses why it exists. Albert Einstein stated: "Science without religion is lame, religion without science is blind," suggesting the two fields can complement one another. Francis Collins, director of the Human Genome Project, argues that scientific discovery can lead to a deeper understanding of God's creation. Some maintain that science and religion are in conflict, with scientific inquiry undermining the need for belief in God. However, others point out that many foundational scientists were religious (Newton, Galileo, Mendel), and that scientific laws themselves might be seen as evidence of an orderly creator. The relationship remains a subject of ongoing philosophical and theological debate, with perspectives ranging from complete conflict to full compatibility.

Conclusion

The debate over the existence of God is unlikely to be resolved anytime soon. Both sides offer compelling arguments: theists point to the existence of the universe, the apparent design in nature, and the moral law as evidence for a creator, while atheists argue that the presence of evil, the incoherence of the concept of God, and the lack of empirical evidence challenge the idea of an all-powerful deity.

Ultimately, whether one believes in God depends on a combination of personal experience, philosophical reasoning, and the weight one places on different types of evidence. For some, the existence of God provides a meaningful framework for understanding life, while for others, the absence of convincing evidence leads them to doubt. What is clear, however, is that the God debate will continue to shape philosophical, theological, and scientific thought for generations to come.