The argument from reason is an argument for the existence of God based on the nature of reason and rationality. It claims that theism, specifically Christian theism, best accounts for the existence and nature of reason, while atheistic worldviews cannot adequately account for reason and rational thought. The argument was formulated and popularized by Christian philosopher and apologist C.S. Lewis.
At its core, the argument from reason states that rational thought itself presupposes the existence of God. If God does not exist, then there is no basis for rational thought, since atheistic materialism reduces thoughts to merely neurochemical reactions in the brain. But clearly rational thought does exist – otherwise we could not reason, form arguments, make inferences, etc. Therefore, there must be a rational foundation for rational thought, which theism provides but atheism does not.
C.S. Lewis argued that there are three main alternatives when it comes to explaining reason and rationality:
- Reason is an illusion.
- Reason is the unintended byproduct of irrational causes.
- Reason has a rational foundation.
The first option, that reason is an illusion, is self-defeating. As soon as you make the claim that reason is illusory, you are using reason to make that claim, which defeats the original premise. Reason cannot both exist (in order to make the argument) and not exist (if it is illusory) at the same time.
The second option states that reason developed through non-rational evolutionary causes such as natural selection acting on random genetic mutations. However, the statement “reason developed through non-rational causes” implicitly relies on the validity of reason in order to make that logical deduction. You cannot use reason to argue that reason itself developed without reason. This is circular and incoherent.
The third option is that reason has a rational foundation. This maintains that reason is objectively valid and sound. But what could serve as the rational grounding for reason itself? Lewis argued that theism, specifically Christian theism, provides the necessary explanatory foundation. The transcendent, immaterial, eternal God who exists beyond space and time created humans as rational, reasoning beings in His image (Genesis 1:27). God Himself is supremely rational, and He implanted human beings with reason and rationality as part of being made in His likeness.
Therefore, Lewis concluded that the existence of rational thought points to and requires the existence of a supremely rational God as the source. Without God, reason has no basis. Atheism has no explanatory power for reason since atheism only posits the natural, material world as all that exists. Matter alone cannot produce or ground reason. Only the eternal, rational God provides the necessary foundation.
Lewis argued that every time we make a rational inference, we are relying on the theistic worldview. He stated it this way: “One absolutely central inconsistency ruins [the atheistic worldview]…It is the fatal flaw…which shows this pretentious edifice to be a house of cards. That flaw is the very neatness with which it is so flexible. The materialist theory can explain everything, and explain it in many different ways…” (Miracles, Chapter 3).
In other words, atheism fails the test of being able to provide a foundation and explanation for reason itself. Materialism reduces everything to physical processes, but physical processes alone cannot account for the immaterial nature of logical thought. Only theism maintains that humans have both physical and non-physical natures since they are created by an immaterial God.
The argument from reason also defeats scientific materialism, which says that science alone can explain all of reality. But science itself relies on logical reasoning. So to claim reason is illusory or strictly material would undermine science as well. Science requires the validity and soundness of reason to even do science. Therefore, the existence of reason points to God as its basis.
In his book Miracles, Lewis gave this succinct summary of the argument: “Unless human reasoning is valid no science can be true. It follows that no account of the universe can be true unless that account leaves it possible for our thinking to be a real insight. A theory which explained everything else in the whole universe but which made it impossible to believe that our thinking was valid, would be utterly out of court.” (Chapter 3).
The argument from reason has been formulated in both deductive and abductive forms. The deductive form is as follows:
- No worldview other than theism can account for the existence of rationality/reason.
- Reason/rationality exists.
- Therefore, theism is true.
And the abductive form:
- Reason/rationality exists.
- The best explanation for the existence of reason/rationality is the existence of God.
- Therefore, it is reasonable to believe God exists.
In summation, the argument from reason claims that the existence of reason itself requires the existence of God. Without God providing the necessary preconditions for reason, we could not have confidence in rational thought since it would have arisen from irrational, material processes. But we clearly do use reason. Therefore, it follows that there must be an eternal rational God as the basis for reason. Only Christianity provides the grounding in an eternal, immaterial, supremely rational divine mind as the source of human reason. The argument from reason powerfully demonstrates that denying God’s existence leads to irrationality.
Key Points about the Argument from Reason
Here are some key points to understand about the argument from reason:
- It was popularized by C.S. Lewis but builds on insights from past Christian thinkers like Augustine.
- It states that reason/rationality requires a rational foundation, which only theism can provide.
- The existence and validity of reason point to the existence of God.
- Without God, reason would arise from non-rational causes, undermining confidence in reason.
- It shows atheism/materialism cannot account for reason itself.
- The deductive form shows theism is the only worldview that accounts for reason.
- The abductive form says God’s existence best explains the existence of reason.
- It defeats the claims of scientific materialism and philosophical naturalism.
- Christian theism maintains humans are rational beings because we are made in God’s image.
- The supremely rational eternal God grounds human reason and rationality.
Understanding these key points provides a framework for understanding the argument from reason. The core claim is that denying God’s existence leads to irrationality, while Christian theism coherently explains the existence of reason itself.
Objections to the Argument from Reason
There are several main objections that have been raised against the argument from reason over the years. Understanding the common counterarguments can help strengthen the argument by showing where the objections falter.
The Genetic Fallacy Objection
One common objection is that the argument from reason commits the genetic fallacy. The genetic fallacy ignores the validity of a claim and instead only focuses on where the claim came from. Critics say the argument from reason does this by attacking the origins of reason in naturalism rather than the validity of reason itself.
In response, defenders note the argument from reason does not commit the genetic fallacy because it is not claiming “reason came from irrational processes, therefore reason is invalid.” Rather, it is recognizing the intrinsic contradiction in the claim “reason came from non-rational causes.” The issue is not where reason came from, but that however reason arose, it must have a rational foundation.
The argument recognizes reason is valid but states reason needs to arise from rational foundations. Attacking the irrational origins of reason in atheism is not a genetic fallacy but rather exposing the incoherence built into the atheistic origins claim itself.
The Evolution Objection
Another common objection is that evolution can account for the development of reason through natural selection. As human brains evolved, the capacities for reason emerged as advantageous traits that improved survival changes.
In response, evolution does not rescue the atheist position because evolution is an irrational process driven by random mutations. An unguided process dependent on chance mutations cannot produce the immaterial realities of logic, truth, and reason. As philosopher Angus Menuge notes, “Irrational causes only produce another iteration of themselves.” Atheism has no rational source to impart reason into the evolutionary process.
Additionally, natural selection can only select for behaviors and traits that improve survivability. But many forms of rational thought have no impact on survival or reproduction. Higher mathematics, ethics, metaphysics cannot be accounted for by their survival value. But they are real and valuable forms of reason.
The Reason is Physically Based Objection
Other critics argue that modern neuroscience shows that reason and rationality are based in the physical brain. Rational thought emerges from the brain’s neuronal complexity. Therefore, reason is in fact physically based, not an immaterial reality that requires a divine source.
However, this fails to explain how physical neuronal firings produce the abstract universals of logic and reason. No amount of neuronal connections can bridge the gap to generate the laws of logic from purely material processes. Electrons and neurons do not reason; minds do. Studies may show correlations between brain activity and reason, but correlation does not prove causation or explanation.
Additionally, the content of rational thought often concerns things outside of the physical world, like ethics, mathematics, logic, or metaphysics. So there must be more to reason than just brain chemistry.
As philosopher J.P. Moreland notes, “It is one thing to say that brain events are part of reason. It is quite another to say that brain events alone are identical with reason.” Theism offers the best explanation for the physical and non-physical aspects of reason coming from an eternal divine mind.
The Laws of Logic Objection
Some critics argue that the laws of logic themselves are brute, necessary features of reality that exist whether God exists or not. For example, the law of non-contradiction would hold true even in an atheistic universe. Since the laws of logic seem to be necessarily true, they do not require God’s existence.
Defenders of the argument from reason respond that God is the ontological ground of all necessary truths. God’s own rational nature is the basis for realities like logical laws to be true in all possible worlds. Though they are necessarily true, they require a Necessary Being (God) as their ground and source. Without God, there is no basis for immutable truths. So even logical laws point to a divine foundation.
Additionally, the fact that the laws of logic are immaterial realities points to an immaterial source in God. They provide evidence of realities beyond the physical world which a materialist worldview struggles to explain.
So in summary, the main objections do not refute the force of the argument from reason. They fail to explain how reason could emerge from non-rational causes. The deductive and abductive forms show that God’s existence is the only coherent explanation for the realities of reason, logic, truth, and rational thought that we rely on daily.
Examples of the Argument from Reason
Looking at examples of the argument from reason in action can further illustrate its force:
- Mathematics: Mathematics is a profoundly rational system of thought. But math is not a physical reality present in the universe. The number 4 does not exist out in the world. Mathematical concepts concern abstract realities that cannot be reduced to mere matter. The very existence of mathematical reasoning requires a rational source beyond a purely material universe. This points powerfully to a supremely rational God as the ground of mathematical reason which is invested in humans as His image bearers.
- Morality: We recognize objective moral truths like murder is evil and kindness is good. But these moral categories of good and evil cannot be explained by atheism which only recognizes physical matter. Therefore, the existence of moral reasoning indicates we are more than just material beings and that objective moral realities exist, grounded in God’s moral nature.
- Abstract Thoughts: Our minds have the capacity to dwell on abstract concepts removed from the physical world such as justice, beauty, ethics, meaning, etc. But atoms moving around in the brain cannot explain contemplating these conceptual realities. Their existence points to the reality of human souls and minds beyond the physical realm, best explained by theism.
- The Existence of Truth: Truth by nature is that which corresponds to reality. Believing in truth assumes that there are objective realities which exist outside of our minds. But materialism struggles to account for the concept of truth pointing to objective reality. Our recognition of truth points to God as the ground and basis for knowable, objective truths that exist for us to discover.
These examples and many more show the concrete outworking of the argument from reason. In each case, a key aspect of human reasoning and rationality finds its best explanation in the existence of the rational Christian God rather than in atheistic materialism.
Implications and Conclusions
The argument from reason has profound implications for the truthfulness of the Christian worldview:
- It shows that denying God’s existence leads down the road to irrationality by undermining reason itself.
- Christian theism alone provides the necessary grounds for reason, logic, truth and the abstract concepts humans reflect on.
- It strongly points to humans having both physical and spiritual natures, contrary to materialism.
- The very existence and use of reason reflects God’s image imprinted on humanity.
- It shows that a supreme rational Mind is the ontological ground of reality, rather than just blind matter.
- The transcendent source of human reason is revealed in the Bible as the eternal logos or divine Logic of God (John 1).
In conclusion, the argument from reason powerfully shows that denying God’s existence leads to absurdity and incoherence. It proves that the existence of reason itself points to and requires the existence of God. As the source of the rational foundations of reality, God’s own supremely rational nature grounds the human capacity to reason, think rationally, and draw logical inferences. The argument from reason therefore provides a compelling case that the Christian faith is true because only the biblical worldview can account for the existence of reason.