What Is the Argument from Reason, and How Does It Destroy Atheism?
What did C. S. Lewis say about faith and reason?
This is the argument from reason, and the argument from reason is a transcendental argument. Its most famous proponent was C. S. Lewis. But I’m going to start by telling you what philosopher Paul Gould, from Palm Beach Atlantic University, says about it. This is Paul Gould’s introduction to the argument from reason—and then I’ll tell you what C. S. Lewis himself says about it.
So listen carefully to this, because this is a good, solid argument. Paul Gould explains C. S. Lewis’s articulation of the argument from reason on his website thusly:
“If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true.
And hence, I have no reason for supposing my brain to be composed of atoms.
Naturalism discredits our processes of reasoning—or at least reduces their credit to such a humble level that it can no longer support naturalism itself.”
Let me pause here. Naturalism is the belief that only the world of matter and energy and natural processes exists.
C. S. Lewis Philosophy
Gould continues: Lewis is noting a deep conflict between naturalism and the reality of reason. On the other hand, on theism—specifically, I would say, Christian theism—reason and intelligence are a natural fit. A rational God exists, and part of what it means to be created in the image of this rational God is to possess intelligence.
Thus, an argument from reason to God could be formulated as follows:
If the natural world is intelligible, then God exists.
The natural world is intelligible.
Therefore, God exists.
Now let’s see what Lewis himself says. This is from The Weight of Glory and Other Addresses. Lewis writes:
“This one absolutely central inconsistency ruins the naturalistic worldview.
The whole picture professes to depend on inferences from observed facts.
Unless inference is valid, the whole picture disappears.
Unless reason is an absolute, all is in ruins.
Yet those who ask me to believe this world-picture also ask me to believe that reason is simply the unforeseen and unintended byproduct of mindless matter at one stage of its endless and aimless becoming.
Here is flat contradiction.
They ask me at the same moment to accept a conclusion and to discredit the only testimony on which that conclusion can be based.”
What Is an Argument From Reason?
So here are the premises of Lewis’s argument, as they’ve been defined:
No belief is rationally inferred if it can be fully explained in terms of non-rational causes.
In other words, if a belief is formed purely—or originally—by non-rational causes… if it can be ultimately explained by non-rational causes, then that belief is, by definition, non-rational. Are you following me? You might even say irrational.
If naturalism is true, then all beliefs can be fully explained in terms of non-rational causes.
Okay, so you know where we’re going here with the conclusion:
Therefore, if naturalism is true, then no belief is rationally inferred.
That’s the natural outcome of premise one and premise two.
Transcendental Argument
Now, item four:
We have good reason to accept naturalism only if it can be rationally inferred from good evidence.
Therefore:
There is not, and cannot be, a good reason to accept naturalism.
This is sort of like the evolutionary argument against naturalism from Alvin Plantinga. It’s very reminiscent of the transcendental argument for God from Cornelius Van Til and Greg Bahnsen—and yours truly—but it’s a little different. This is an argument from reason.
Naturalism Defeated
If naturalism is true, then no beliefs are rational.
And if no beliefs are rational, then naturalism is not rational.
And you should only believe in things if they are rational.
Therefore, you shouldn’t believe in naturalism.
It’s pretty cut and dry, I’d say.
🎥 Want to Watch the Full Debate?
If this whet your appetite for more, you need to watch the full discussion on the Argument from Reason. We dive deep into the logic, theology, and implications of this devastating critique of naturalism.
👉 Watch it now on YouTube: https://youtube.com/live/eF5DKrDqCI8
Don’t just read about the argument—see it in action.
⚒️ Join the Hammer & Anvil Society
Are you a Christian man who wants to sharpen your mind, harden your theology, and forge unbreakable convictions? Then join the Hammer & Anvil Society, our community for men committed to thinking deeply, standing firm, and contending boldly for the faith once for all delivered to the saints.
👊 Weekly challenges. High-level discussion. Real accountability.
🔨 Because iron sharpens iron—and you were made for more.
👉 Apply to join today. Act today and you can try it for eight weeks absolutely free.