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Introduction

In philosophical and theological discourse, a curious paradox arises when one challenges the very foundations of free will or the existence of God using the tools that those concepts underwrite. In simple terms, to argue against the existence of free will, one must engage in deliberate reasoning and judgment—activities that seem to presuppose free will. As one commentator quips, “When you decide after careful deliberation that free will does not exist, you demonstrate that it does exist.”. This self-referential contradiction highlights the tension between deterministic worldviews and the lived experience of choice. An analogous paradox appears in theology: using reason or moral judgment to deny the existence of God can seem self-defeating if those very faculties are thought to originate from a divine source. In the words of one argument, it is like saying “Presupposing that God exists, God does not exist,” which is a logical contradiction.

These paradoxes touch on fundamental questions about human agency, rationality, and the ultimate ground of truth. Can one coherently reject free will without undermining the credibility of one’s own argument? Can one refute God’s existence using laws of logic or moral principles that, under a theistic view, only make sense if God exists? This paper explores these questions through philosophical, theological, and scientific perspectives, drawing on the insights of thinkers such as Immanuel Kant, David Hume, St. Augustine, and St. Thomas Aquinas. We examine the historical context of the debate, the main arguments that identify a paradox, and the counterarguments from determinist and atheistic perspectives, to assess whether these challenges truly involve a self-contradiction or whether they can be resolved through careful reasoning.

Historical Context

Debates over free will and God’s existence have deep roots in Western thought. The tension between human freedom and determinism was already noted by ancient philosophers, and questions about God’s role in human reason have been discussed for centuries. Understanding the stances of influential thinkers provides a backdrop for the modern paradox in question:

Augustine (354–430 CE): Augustine insisted on human free will, arguing that without it God’s punishments and rewards would be unjust (“evil deeds are punished by the justice of God… They would not be punished justly if they had not been performed voluntarily”). He also taught that the eternal truths we grasp (for example, in mathematics or ethics) must reside in an eternal mind, namely God​

reasons.org

. Thus, for Augustine, using one’s reason or will to defy God is misguided, since those capacities flow from God.

Thomas Aquinas (1225–1274): Aquinas likewise argued that free will is real—“otherwise counsels, exhortations, commands, prohibitions, rewards, and punishments would be in vain”—underscoring that our moral and legal practices presuppose human freedom. He also believed that human reason can discover certain truths about God (as shown in his “Five Ways” proofs of God’s existence), reflecting a fundamental harmony between reason and faith. For Aquinas, using reason itself is a God-given gift; thus to deny God by means of reason is paradoxical, a misuse of the very faculty bestowed by God (though he admitted some truths of faith do exceed what reason can demonstrate).

David Hume (1711–1776): In contrast, David Hume defined free will in a modest, compatibilist way (as the ability to act according to one’s will without external constraint). Therefore, he saw no contradiction in viewing human choices as determined while still calling them “free” in a practical sense. Hume was also critical of traditional proofs of God and held that our reasoning and morals are grounded in human nature and experience rather than in a divine source. He would reject the idea that logic or ethics depend on God, or that denying free will is self-defeating—he thought such debates often arose from semantic confusion.

Immanuel Kant (1724–1804): Kant tackled free will by suggesting a dual perspective: determinism governs the empirical world, but we must regard ourselves as free in order to be morally responsible. In fact, the very concept of moral duty, for Kant, presupposes that we can choose to follow the law or not, so freedom is a necessary postulate of morality. Regarding God, Kant denied that we can prove God’s existence through pure reason, but he argued that the ideas of God and immortality function as postulates of practical reason. In other words, assuming God’s existence and a just afterlife helps make sense of the moral order (for example, the hope that virtue will ultimately be rewarded). Kant thus held that freedom and a moral divine order are things we must assume for the sake of ethical consistency, even though they cannot be known empirically.

This historical overview shows a range of perspectives. Augustine and Aquinas emphasize that free will and rational truth-seeking are grounded in God, implying that denying either undercuts the basis of reasoning and morality. Hume detaches human rationality from the divine and redefines free will in a modest way, thereby seeing no paradox in using reason to question robust free will or God’s existence. Kant acknowledges the apparent contradictions but finds a path to salvage freedom and moral faith by distinguishing between what we must assume for practical purposes and what we can theoretically know. These viewpoints set the stage for the analysis of the paradox itself.

Main Arguments

The core issue is whether there is a self-contradiction involved when someone denies the reality of free will or the existence of God while relying on faculties or principles that depend on them. We examine the reasoning behind these claims of paradox in two parts: one for free will, and one for the concept of God.

The Paradox of Challenging Free Will

Those who argue that it is paradoxical to deny free will point out that the act of arguing, choosing, or reasoning appears to presuppose the very freedom being denied. If a person writes an essay or gives a speech to convince others that free will is an illusion, we normally assume this person has deliberated, weighed evidence, and chosen to adopt that position. In doing so, they behave exactly as someone with free will would behave. The irony, as noted earlier, is that when you carefully deliberate to conclude that free will doesn’t exist, you have demonstrated your own free will in the very act of deliberation. The argument here is that reasoning is an active process that entails selecting among alternatives based on reasons. To say “I reached the conclusion that free will is false by rational consideration” implicitly means “I was not utterly compelled by fate or physics to this conclusion—I considered other possibilities and chose this because it seemed best.” That is effectively an affirmation of one’s freedom to reason.

Another way to frame this is to consider what it would mean if free will truly did not exist. If all our thoughts and actions are wholly determined by prior causes (be they divine predestination, physical laws, or biological processes), then any conclusion we reach—including “free will is an illusion”—is not chosen because it’s true, but simply happens because of preceding events. The ideal of rational inquiry is that we follow evidence and logical principles to arrive at true beliefs; that ideal assumes an agent who can respond to reasons and is not just pushed along by blind forces. In everyday life, giving advice, making requests, or debating issues only makes sense if we believe the other person has the freedom to change their mind or behavior. Otherwise, such efforts are futile. Thus, the practice of exchanging arguments itself presupposes that participants have some degree of free agency to weigh the arguments. This is essentially the point Aquinas made long ago: without free will, concepts like counsel, commands, or criticism lose their meaning.

Contemporary discussions bring in findings from science to challenge free will, yet these often inadvertently reinforce the paradox. For example, neuroscientist Benjamin Libet’s experiments in the 1980s showed that unconscious brain activity (the readiness potential) precedes a person’s conscious decision to perform a simple action by a fraction of a second. Some interpret this as evidence that the brain “decides” before the conscious mind is aware, suggesting our feeling of choosing freely is an illusion. Hard determinists like Sapolsky use such evidence to argue that all our choices are just biochemical events outside our control. However, consider what is happening when scientists and philosophers present these findings to argue against free will: they are compiling data, constructing logical arguments, and appealing to our reason. In doing so, they treat their audience as capable of rational evaluation and free judgment — exactly what would be impossible if we were nothing more than automata. If the audience truly had no choice but to believe whatever their neurons dictate, the whole exercise of providing reasons and evidence would be pointless. The determinist might respond that we are determined to go through these motions of debate, but at that point the concept of persuasion or objective truth-seeking loses its force. The paradox remains that one must assume one’s capacity for free, rational thought in order to meaningfully engage in disputing free will.

In summary, the argument for a paradox is that denying free will undercuts the credibility of the reasoning used to make that denial. If we truly believed we have no freedom in our thinking, we would have to doubt all of our conclusions as inevitabilities rather than insights. Hence, even the skeptic implicitly trusts in his or her rational agency when arguing about free will. This doesn’t prove that humans have metaphysical free will, but it suggests that in practice we cannot avoid presuming some degree of autonomy when we engage in any kind of truth-directed discourse.

The Paradox of Challenging God’s Existence

A parallel argument appears in theological contexts: using reason, logic, or moral judgment to argue against God’s existence can be seen as implicitly relying on God. This view is especially advanced by proponents of presuppositional apologetics in Christian philosophy. Their claim is that the very possibility of rational thought, logical principles, and objective moral values is founded on the existence of God, whether one acknowledges it or not. From this perspective, whenever someone engages in logical argumentation or presumes a universal moral law, they are “borrowing” from a theistic worldview. One apologist argues, for example, that even an atheist’s arguments carry an unstated premise: “every proposition we make has an invisible disclaimer at the beginning: ‘Presupposing that God exists…’.”. In other words, to use logic at all is to operate within a divinely grounded rational order. Thus, a person who declares logically that “God does not exist” would be performing an inherently contradictory act—using a tool (logic) that only exists because of the very being whose existence they are denying.

Classical theologians offered related ideas. Augustine, as mentioned, reasoned that our ability to apprehend eternal and immutable truths points to a divine eternal mind​

reasons.org

. Aquinas likewise argued that the intelligibility and orderliness of the universe (and our capacity to understand it) reflect the rationality of a Creator. If they are right, then to use the light of reason while rejecting the sun (God) that illuminates it is perverse. Another facet of this paradox appears in moral arguments. For instance, the problem of evil claims that the existence of suffering and injustice is incompatible with an omnipotent, good God. Some theists counter that this argument itself presupposes a solid standard of good and evil. We recognize something as “evil” only by measuring it against a moral law. If one denies God, one could ask, what is the basis for an objective moral law? A common theistic argument is that without God, moral values lack an absolute foundation. In that case, invoking the reality of evil to disprove God could be seen as paradoxical: the argument needs real moral truths (to say evil is truly evil) while the worldview of the arguer might not have a grounding for such truths.

The thrust of the “God paradox” argument is that reason, truth, and goodness are not neutral features of the universe but reflections of a divine source. If one accepts that premise, then trying to deploy reason or morality against God is akin to sawing off the branch on which one sits. The skeptic’s act of denial would collapse under its own weight because it relies on the very thing being denied. However, it should be noted that this argument is compelling only if one already grants that logic or morality indeed require a divine foundation. This is precisely what the critic would contest, which leads us to the counterarguments.

Counterarguments and Rebuttals

Critics of the paradox claim argue that one can deny free will or God without any incoherence, by challenging the idea that reason or morality depend on those entities. Here are several major counterarguments, along with responses from the defenders of the paradox.

Objection 1: Determinism and reason.
Determinists argue that rational deliberation can be fully understood in deterministic terms. Even a computer or AI can follow logical rules without any “free will”; likewise, a human brain could produce valid reasoning while being governed by physical laws. Thus, they claim there is no contradiction in arguing against free will: the argument was caused by evidence and logic, and if it is sound it will causally persuade others—free will or not. What matters is the reliability of our reasoning process, not some metaphysical freedom of the will.

Rebuttal: Critics respond that if our beliefs are entirely produced by non-rational forces, it undercuts our justification for them. We normally trust a conclusion because we think it was reached by evaluating reasons; if instead it happened inevitably, like a chemical reaction, can we still call it “true” or “rational”? Some philosophers warn that a purely deterministic, naturalistic view might undermine our trust in reason itself. The debate here centers on whether logical justification requires a thinker who could have considered alternatives (thus exercising freedom), or whether deterministic minds can still reliably track truth.

Objection 2: Secular foundations of reason and morality.
Atheists and secular philosophers contend that neither logic nor ethics depend on God. The laws of logic are seen as inherent features of reality or human thinking that we use because they work, not because God decreed them. Similarly, moral values can be rooted in human nature or rational principles (such as maximizing well-being or respecting others’ rights) without invoking a divine lawgiver. From this perspective, an atheist using reason and morality to critique religion is not “borrowing” from theism—they are employing universal human tools. There is no paradox, because logic and moral insight are understood as products of the natural order or of human culture.

Rebuttal: Defenders of the paradox argue that the secular account leaves some questions unresolved: Why do logical truths hold universally? Why do moral obligations feel binding? The theist posits God as the answer—logic reflects God’s rational order, and morality reflects God’s character or commands. Without that foundation, they argue, one is left with brute facts (logic “just is”) or moral relativism. The atheist may respond that not every given (like a logical law) requires a further explanation, or that morality can be grounded in rational consistency and human empathy. Thus, each side accuses the other of an incomplete worldview: the secular side is said to take reason and morality for granted, while the religious side is said to introduce unnecessary assumptions.

Objection 3: Redefining free will or mind.
Some thinkers avoid the free will paradox by adopting a different definition of free will or a different understanding of the mind. Many scientists and philosophers accept that humans make choices and reason, but they say these processes are fully caused by prior events in the brain and environment. In this compatibilist view, “free” simply means we act voluntarily (without external coercion), even if our decisions have determining causes. Therefore, one can deny ultimate free will while still relying on deliberation and rationality—there is no self-contradiction, because one isn’t denying that we think and choose, only explaining how we do so. Others even suggest that the feeling of free agency is an evolved illusion we cannot shake; recognizing this illusion doesn’t stop us from reasoning or acting, so practically there is no paradox in everyday life.

(In response,) proponents of the paradox might say this stance changes the subject rather than resolving the issue. Still, it shows that a person can reject a certain idea of free will yet consistently continue using their mental faculties and moral judgment without obvious hypocrisy.

Conclusion

In examining this paradox, we see how deeply issues of freedom and the divine are intertwined with the conditions of our thinking. For one camp, if we abandon the assumption that humans have free agency or that reason and morality are grounded in something transcendent, we risk undermining the very notions of objective truth and moral responsibility. From this perspective, the skeptic who denies free will or God is in danger of “sawing off the branch” that supports rational discourse and ethics.

However, others remain convinced that we can explain and justify reason and morality in secular terms. They view the paradox as a challenge to refine our understanding of human cognition and values, rather than proof that a supernatural foundation is required. By reinterpreting free will in compatibilist terms and finding non-theistic grounds for ethical norms, they aim to preserve coherence without invoking metaphysical entities.

Perhaps the most pragmatic lesson is that we inevitably behave as if we have free will and as if certain moral values and logical laws hold true. Some philosophers (like Kant) suggest we must proceed with these assumptions in practical life, even if we remain uncertain about their ultimate metaphysical status. In the end, grappling with this puzzle forces both believers and skeptics to examine the preconditions of their arguments. It highlights the need for any worldview to account for the conditions that make reasoning and moral judgment possible. In that sense, the paradox—whether or not one finds it decisive—usefully illuminates the mutual entanglement of faith, reason, and human agency in our pursuit of truth.

Sources:

1. Horgan, J. (2023, November 5). Free Will and the Sapolsky Paradox. Cross-Check (blog). Scientific American. “When you decide after careful deliberation that free will does not exist, you demonstrate that it does exist.”
2. Settecase, J. M. (2017, October 25). This is Apologetics: an Argument from Logic. Settecase.Wordpress.com. “Every proposition we make … ‘Presupposing that God exists….’ … a ‘logical’ denial of God’s existence is … ‘Presupposing that God exists, God does not exist.’”
3. Aquinas, T. (ca. 1270). Summa Theologiae I, Q.83. “Man has free-will: otherwise counsels, exhortations, commands, prohibitions, rewards, and punishments would be in vain.”
4. Augustine of Hippo (ca. 395). On Free Choice of the Will. “Evil deeds are punished by the justice of God. They would not be punished justly if they had not been performed voluntarily.”
5. Augustine of Hippo (ca. 400). On the Trinity (as summarized in Reasons to Believe). “Since truth must reside in a mind, Augustine argued that these eternal truths are grounded in the eternal mind of God.”​reasons.org
6. Hume, D. (1748). An Enquiry Concerning Human Understanding, Section VIII. “By liberty, then, we can only mean a power of acting or not acting, according to the determinations of the will; … if we chuse to remain at rest, we may; if we chuse to move, we also may.”
7. Kant, I. (1788). Critique of Practical Reason. (Interpretation in [15]). It is necessary to presuppose freedom, “because otherwise it would be unreasonable to hold people responsible… Holding people responsible would not make sense without free will… Therefore, there must be free will in the noumenal world.”
8. Libet, B. et al. (1983). “Time of Conscious Intention to Act in Relation to Onset of Cerebral Activity,” Brain. Neuroscience experiment showing unconscious brain activity (Bereitschaftspotential) ~0.5 s before conscious decision to move.