Q&A: How Do We Know Logic Is Reliable?

Greetings. To offer some preliminary remarks: I admit this question isn’t very theological, it’s much more philosophical, born out curiosity. Nevertheless, I do believe it’s an interesting question that deserves some level of reflection, even for Christians.

With that being said, here’s the question: How do we know our most basic principles of reasoning (the Law of Non-contradiction, Modes ponens, etc.) are true? As you can see, it’s an epistemological question, and I’ve found two main answers to it: (1) We know our logical principles are true through our rational intuition. It only takes a moment to reflect on a logical principle to see it’s truth. I can clearly ‘see’ intuitively that something can’t be both true and false. A tree can’t both exist and not exist. And (2): we can’t even coherently raise doubts about our logical laws, which is evidence for their truth. For instance, trying to argue against the Law of Identity is self-defeating because you have to assume the law is true to argue against it.

My problem with (1) is that it doesn’t satisfactorily answer the question. What exactly is “rational intuition”? What’s the nature of intuition. It seems pretty mysterious to me. More importantly, how do we even know human intuition is reliable? It seems the same applies to attempts to construe intuition in a conceivability sense: Why trust human conceivability as a reliable guide to truth? These concerns make me skeptical of (1).

(2), in my opinion, seems most promising as an answer. If we can’t even coherently doubt a proposition, that appears to be strong evidence that the proposition is true? The problem, however, is that our logical principles are construed as being necessarily true. While not being able to raise doubts against logical laws counts as strong evidence, does it warrant certainty? I’m not sure it does.

BTW, I’ve started listening to the first episode of your podcast. I like what I’m hearing 🙂

— Christian


This is quite an interesting question. If we can’t trust our reasoning, then we’re in deep trouble We would not be able to know anything about anything. We wouldn’t be able to know any scientific truths, we wouldn’t be able to know which candidate is the best one to vote for, we wouldn’t even be able to know that God exists or that Christianity is true (so, I certainly think your question bleeds into theology).

Belief In The Truth Of The Laws Of Logic Is Properly Basic

I would answer the question by affirming both of your proposals. We know it through rational intuition and because you cannot disprove the truth of the laws of logic without appealing to them. Logic is one of those “first principles” that we take be true without reflection, otherwise known as a properly basic belief. Properly Basic beliefs are beliefs that you a perfectly justified in holding to sans an argument for their truth, unless and until you are given some defeater to think your properly basic belief is true. I would say that the reality of the laws of logic and the nine rules of inference are among the properly basic beliefs that we hold. Some other properly basic beliefs would be the existence of other minds outside of my own, the existence of objective morality, and if Reformed Epistemology is correct, the truth of Christianity, though I haven’t studied Reformed Epistemology a whole lot so I don’t take a hard stance on it.

Some properly basic beliefs can have supporting arguments for them (e.g the truth of Christianity), but some cannot even be proven in principle. The truth of the laws of logic and the nine rules of inference would be one of them. You can’t reason logically to the conclusion that the laws of logic and rules of inference hold. Doing so would be question begging as you’d be using the very principles you’re trying to prove!

However, if the validity of the laws of logic and inference are properly basic, as I maintain, then we’re perfectly justified in taking them to be true without having any proof of that.

The Ghost Makes The Machine Rational

Now, the really interesting question is this; which worldview can best account for the validity of our reasoning? I would argue that on atheistic naturalism (which logically entails determinism), and on deterministic views of divine providence, while the laws of logic and inference would still be valid, whether we in our own minds properly evaluate evidence and properly reason to true conclusions would simply be the result of luck. If we reason to true conclusions, it would be simply the result of luck or God’s decree.

Tim Stratton, head of FreeThinking Ministries, formulated an argument that deductively proves the existence of libertarian free will, the soul, and abductively to God’s existence. The premises of the argument demonstrate both the existence of free will as well as the existence of the soul, and it indirectly points to the existence of God. Stratton’s argument goes as follows

1- If naturalism is true, the immaterial human soul does not exist.

2- If the soul does not exist, libertarian free will does not exist.

3- If libertarian free will does not exist, rationality and knowledge do not exist.

4- Rationality and knowledge exist.

5- Therefore, libertarian free will exists.

6- Therefore, the soul exists.

7- Therefore, naturalism is false.

8- The best explanation for the existence of the soul is God.

Premise 1 is true by definition. If Naturalism is true, then we’re just organic robots. If atheism is true, all there is is matter, energy, space, and time. There are no “souls” or “spirits”. Premise 1 is true by its very definition! Naturalism asserts that all that exists are natural things, in other words, everything that can be found on the periodic table. If there were any supernatural entities (which a human soul would definitely be), then naturalism, according to how its defined, would be false. What about Premise 2? Premise 2 is tantamount to saying “If all that exists is nature, then all things are controlled by the laws of physics and chemistry. If all that exists is nature, natural processes determine all things”. If it is the case that there is no immaterial soul, then it follows that we’re just “molecules in motion” as Frank Turek likes to put it. If Naturalism/Atheism is true, we are nothing but automata. All of our movements, feelings, thoughts, and opinions are causally determined by electrochemical processes in our brains, molecules, and atoms bumping about, and other physical processes. “You” are a meat machine. As geneticist Francis Crick put it “Your joys and your sorrows, your memories and your ambitions, your sense of identity and free will, are in fact no more than the behaviour of a vast assembly of nerve cells and their associated molecules.”1

So if naturalism is true, we don’t have souls, and if we don’t have souls, we don’t have free will. We’re just “molecules in motion”. What about premise 3? Is it true that “If libertarian free will does not exist, rationality and knowledge do not exist?” I think so! Tim Stratton, in his article “The Freethinking Argument In A Nutshell”, wrote “Premise (3) is equivalent with ‘if all things are causally determined, then that includes all thoughts and beliefs.’ If our thoughts and beliefs are forced upon us, and we could not have chosen better beliefs, then we are simply left assuming that our determined beliefs are good (let alone true). Therefore, we could never rationally affirm that our beliefs are the inference to the best explanation – we can only assume it. Here is the big problem for the atheistic naturalist: it logically follows that if naturalism is true, then atheists — or anyone else for that matter — cannot possess knowledge. Knowledge is defined as ‘justified true belief.’ One can happen to have true beliefs; however, if they do not possess warrant or justification for a specific belief, their belief does not qualify as a knowledge claim. If one cannot freely infer the best explanation, then one has no justification that their belief really is the best explanation. Without justification, knowledge goes down the drain. All we are left with is question-begging assumptions.”2

William Lane Craig put it this way; “There is a sort of dizzying, self-defeating character to determinism. For if one comes to believe that determinism is true, one has to believe that the reason he has come to believe it is simply that he was determined to do so. One has not in fact been able to weigh the arguments pro and con and freely make up one’s mind on that basis. The difference between the person who weighs the arguments for determinism and rejects them and the person who weighs them and accepts them is wholly that one was determined by causal factors outside himself to believe and the other not to believe. When you come to realize that your decision to believe in determinism was itself determined and that even your present realization of that fact right now is likewise determined, a sort of vertigo sets in, for everything that you think, even this very thought itself, is outside your control. Determinism could be true; but it is very hard to see how it could ever be rationally affirmed, since its affirmation undermines the rationality of its affirmation.”3

Is Premise 4 true? Yes. As you yourself pointed out, Christian,. anyone who tries to argue against rationality and knowledge has to employ the very things he’s trying to disprove. To deny this premise is to affirm it.

Given the truth of the 4 premises, steps 5-7 follow. Libertarian free will exists, therefore the soul exists, therefore naturalism is false.

As Stratton will tell you, this argument has 3 deductive conclusions and 1 inductive conclusion. The deductive conclusion is that naturalism is false, the inductive conclusion is an inference that God is the best explanation for why the human soul exists. It makes more sense to me to think that if souls exist, immaterial minds, then there was a “Mega Mind” that created all of them. Abductively reasoning that God is the best explanation for the existence of the human soul would require showing that only Theism can adequately account for the soul’s existence, while atheistic alternatives such as Emergentism fail. But, I won’t go any further into The FreeThinking Argument’s inductive conclusion than this. Check out Stratton’s writings on this yourself at http://freethinkingministries.com/

This argument kills 2 birds with 1 stone. Those birds are named Atheism and Calvinism (or at least the versions of Calvinism which employ a deterministic view of divine providence).

By the way, this is one of my portions of beef with presuppositional apologetics. As you could infer from what I’ve said in this article so far, I certainly think God must ontologically precede the validity of our reasoning and deliberation process, but you don’t need to know that God exists in order to know that you can reason properly. I would agree with the presupp crowd that you can’t account for the validity of the rational process without invoking an intelligent Mind who fashioned our minds, but that doesn’t mean you know the intelligent Mind exists as a result of knowing the rational process.

You can know an apple exists without knowing they come from trees. Presuppositionalists are always conflating the order of ontology with the order of epistemology.


Hopefully, this satisfactorily answered your question concerning whether we’re justified in believing the truth of the laws of logic and the nine rules of inference. My answer was really short, so I thought I thought I’d throw in Stratton’s FreeThinking Argument in there since the topic of your e-mail and subject matter of his argument are closely related.

Finally, I’m glad you like the podcast. Be sure to subscribe to it on iTunes, Stitcher, Spotify, Radio Public, Pocket Casts, or Anchor.fm/evan-minton. Or subscribe to the sister site CerebralFaithPodcast.blogspot.com for listening to it on your browser.


1: Francis Crick, The Astonishing Hypothesis, 1994 cited in Mariano Artigas, The Mind of the Universe: Understanding Science and Religion, Templeton Foundation Press, 2001 p. 11.

2: Tim Stratton, “The FreeThinking Argument In A Nutshell”, November 30th 2015, http://freethinkingministries.com/the-freethinking-argument-in-a-nutshell/

3: William Lane Craig, from the article “Q&A: Molinism VS. Calvinism: Troubled By Calvinists”, – http://www.reasonablefaith.org/molinism-vs-calvinism

If you have any questions about Christian theology or apologetics, send Mr. Minton an E-mail at CerebralFaith@Gmail.com. It doesn’t matter whether you’re a Christian or Non-Christian, whether your question is about doubts you’re having or about something you read in The Bible that confused you. Send your question in, whatever it may be, and Mr. Minton will respond in a blog post just like this one. 

Liked it? Take a second to support Evan Minton on Patreon!

This Post Has 4 Comments

  1. barry

    There are only two ways to "account" for logic itself.

    The first way is to give an answer that is itself in conformity to logic…which would then be begging the question, since why logic works the way it does is precisely the question.

    The second way is to account for logic with an answer that is not premised on logic. This second alternative would avoid the fallacy of begging the question, but its nature as "non-logical" would make it reasonable for the listener to immediately reject it. What fool spends any time thinking non-logical reasoning might be reliable?

    I therefore find that logic is axiomatic and therefore properly exempt from the questions of origin. Any question that forces the answer to be non-logical, or fallaciously question-begging, is an illegitimate question. You may as well pretend it is meaningful to talk about the time before time, as to ask why logic works the way it does.

    Lots of other problems with your article here, for now: I don't see how you can jump from lack of liberartian freewill to inability to correctly discern reality.

    You don't think bugs have libertarian freewill or an immaterial soul, but you surely agree with the rest of the world that they still very often correctly discern their immediate environment sufficiently as to escape predators and find food (i.e., they don't have libertarian freewill, but they manage to obtain correct knowledge of reality nonetheless).

    If bugs can have correct knowledge without needing a soul or libertarian freewill, then human beings can also have correct knowledge without needing a soul or libertarian freewill. Hence, you have not persuasively argued that our correct knowledge of reality "requires" or "necessitates" our having either libertarian freewill or an immaterial soul.

    1. Top Quark

      I therefore find that logic is axiomatic and therefore properly exempt from the questions of origin.

      You may "find" this because it's convenient for your worldview, but unilaterally absolving yourself of the burden of proof for your worldview doesn't mean you don't have such a burden.

  2. Evan Minton

    Naturalism can easily account for knowledge necessary to survival (the four Fs" as they're usually called). But I would argue that's as far as it goes.

  3. Anonymous

    What’s with all of these apologists being foundationalists? Oh, we know logic works because we wouldn’t be able to do logic without it? Brilliant! Also do you even know the difference between basicality and proper basicality without googling it?

Leave a Reply