The law of non-contradiction (LNC) states that A cannot be both A and not A at the same time and in the same way. For example, my car cannot be said to be both in the garage and not in the garage at the same time and in the same way. It could only be both in the garage and not in the garage at the same time if by being “in the garage” in the first instance means something different than it does in the second. For example, it would not be a contradiction if in the first instance I mean to refer to the body shop where my car is being repaired, and in the second instance I mean to refer to its normal storage space where it is currently absent.


Postmodern types disparage the LNC (as with all laws of logic) as a Western invention. No argument is made for such a claim. It is just asserted (any argument offered against the LNC would require them to presuppose its truth, because the premises and conclusion of the argument are not the same as their negation). I have a sneaking suspicion I know why they want to axe the LNC: their worldview is inherently self-contradictory.


Postmodernism claims there is no truth, or that truth cannot be known. And yet, this is a contradiction because the claim that there is no truth, or that truth cannot be known is itself a claim to know something that is true. If the LNC is true, then postmodernism is false. The LNC must be axed to save postmodernism as a worldview.


When you point out the self-referential and incoherent nature of postmodernism, the postmodernist will retort that such an analysis depends on the LNC. Since the LNC is a Western invention, it is inappropriate to subject postmodernism to its criterion. In fact, doing so is just a power play to subjugate others.


What can you say to those who deny the LNC? Greg Koukl has offered a good strategy. When someone claims the LNC is not true, but an invention of Western logic, respond, “So what you are saying, then, is that the LNC is true?” They will protest, “No, I am saying it is not true.” We might respond, “Oh, so you are saying the law of contradiction is true, then. Thank you for clarifying.” Frustratingly they will reply, “No, no. That is not what I am claiming. I am claiming the LNC is not true.” We might graciously answer, “Exactly. That is what I said you said: The LNC is true.”


I would venture to say they would be exasperated with you by this point; aggravated that you would contradict But this exposes the very problem with their claim that the LNC is a Western convention, rather than a universal and necessary feature of human rationality. While they deny the LNC with their lips, they cannot help but to recognize that “is” and “is not” are contradictory, and thus your restatement of their view contradicts their stated view. That is inescapably self-refuting. They cannot deny the existence of contradictions on the one hand, and then correct your contradiction on the other.



For a person who truly believes the LNC is a fiction of Western logic, the only appropriate response to your restatement is a confirmatory, “Yes.” But no one would respond in this way. He would initially seek to correct your contradiction, assuming you have misunderstood him. Even if one dared to respond in this way, I would venture to say he does not believe that which he speaks. For if he believed it, he would have to acknowledge that there was a difference between his believing it, and not believing it. And if such a difference exists, the LNC must be true. The LNC is a first principle of thought that cannot be avoided (rational intuition). It is universal and necessary to all human reasoning—even for those who seek to deny it.


Of course, there are other more persuasive ways of illustrating this truth that guarantee your postmodern friend will come to acknowledge the truth of the LNC. The early 11th century Medieval Muslim philosopher, Avicenna, devised an infamous way for helping someone see the irrationality involved in denying the LNC. Avicenna wrote, “Anyone who denies the LNC should be beaten and burned until he admits that to be beaten is not the same as not to be beaten, and to be burned is not the same as not to be burned” (Metaphysics 1). By no means would I suggest using this tactic, but if this wouldn’t convince your postmodern friend of his error, nothing can!