Liar’s Paradox

Logicians have an exercise called “The Liar’s Paradox” which is used to illustrate a number of things. The basic scenario is this: Your ship goes down, and eventually you drift ashore, where you are greeted by a native who informs you that everyone on this island always lies. Can you believe him? If what he says is true, what he says is false, and if what he says is false, what he says is false. Striking up a conversation faces insurmountable obstacles.

It is a fact of history that the rise of philosophy was accompanied almost simultaneously by the rise of its dark twin, sophistry. The philosopher sought to be a wise man but the sophist was content to be a wise guy, employing language for gain, skeptical that such a thing as truth was worthwhile even if it were within reach.

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What can be done with someone who subverts the very means of communication? What can be done when it is no longer merely a question of the abuse of particular terms but of the rejection of language as a vehicle of truth?

If the choice between philosophy and sophistry is an arbitrary opting for one or the other, then we are all sophists. Philosophers like Plato and Aristotle would have been repelled by the suggestion that their pursuit of truth had no more to commend it than the sophist’s pursuit of power. They had to show that the position of the sophist was incoherent, that the Isle of Liars cannot exist.

John Paul II, in Fides et Ratio, confronts the fact that the Gospel must now be preached in a culture where some at least profess a skeptical relativism, even a nihilism. His first move against this is a little sketch of what he calls “implicit philosophy.” Despite the great divergences among human beings, there appear to be inescapable truths we all share. The pope mentions the principle of contradiction, among a number of other items. This was the principle ultimately at issue between philosopher and sophist, and fittingly so, it being the first principle of all. A thing either is or is not: This principle is observed in every children’s quarrel: “You did!” “I didn’t.” “You did.” “I didn’t,” and so on unto tears or fighting. It is the last refuge.

Such reflections reveal the existence of principles that are accepted by everyone, even by those who try to reject them. The native who met you on the beach had to exempt his revelation from what he was revealing. “We all always lie” has to be exempted from the reach of the revelation, on penalty of being no statement at all. And this means that it is impossible to lie always. It is not just that effective lies are parasitic on the truth, but that even ineffective lies require the contrast of truth to achieve their tawdry status.

The philosopher’s aim in disputing the sophist was not to get the sophist to accept principles he did not yet hold, so much as to show him that there were principles he could not reject. This means that they do not belong to the philosopher, as if the sophist must adopt the philosopher’s position. The sophist already holds the principles he pretends to reject.

You may wonder what I am up to. You might equally well wonder what the pope is up to by bringing up such matters, but his point is one of fundamental importance.

The Holy Father has characterized ours as a culture of death, one that attempts to turn evil into good. These are severe criticisms, so severe that they might seem to be an attack on reason itself, on the natural order. If things are as bad as he says, our nature must seem depraved, rotten through and through.

That is not his point. It is not the Catholic way to be wary of reason or to confuse thinking with defective thinking. With exuberant urgency, the pope sings the praises of reason and becomes almost lyrical about its natural reach. At a time when professional thinkers have given up on reason, it is the pope who reminds them of its range. In so doing, he makes clear how essentially perverse it is for us to abuse our minds and to mimic reasoning for foul and fallacious ends. Talk must not be cheapened to the level of the liar’s paradox because words are rungs in the ladder that leads us to the Word of God. The culture of death is a debased culture, not culture tout court, and relativism and nihilism are not viable philosophical options; they are the negation of reason and of the dignity of the human person.

There is comfort in such reminders. The next time you feel that you have come ashore on the Isle of Liars you can remind yourself that it is an impossible place. But even imaginary gardens have real serpents in them, and the Father of Lies is likely to be slithering about. How it must pain him to remember that he is a fallen angel. Let him lie.


This article originally appeared in the January 1999 issue of Crisis Magazine.


  • Ralph McInerny

    Ralph McInerny was a popular writer, philosopher, and teacher, as well as the co-founder of Crisis Magazine. He passed away on January 29, 2010.

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