There is a moment in almost every public argument about faith when the words stop landing. A citation is read aloud. The verse is clear. The hearer does not receive it. He relocates it, renames it, or asks what it has to do with the topic. The speaker repeats the sentence. The hearer repeats the deflection. Nothing accumulates.

An old warning covers that moment. In the Sermon on the Mount, after telling his hearers not to judge a brother hypocritically, Jesus adds a limit: “Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you.” The line is not a slur. In the world that produced it, dogs were scavengers and swine were unclean. Neither could tell a holy thing from scraps. Pearls thrown into that setting were not merely unused. They were trampled, and the one who threw them risked being torn.

The same counsel appears, in plainer speech, in Proverbs. “Speak not in the ears of a fool: for he will despise the wisdom of thy words.” The verses just before it describe a meal with a man whose heart is not with you. You spend pleasant words.

You leave having lost them. The fool of that proverb is not the untaught. He is the man who has already decided against instruction. What he returns is not confusion. It is contempt.

A recent exchange on video makes the pattern easy to watch. A former Muslim presses a Muslim speaker on whether Islamic law treats people equally before the law. He cites the Quran’s inheritance rule that a male receives the share of two females.

The speaker suggests the line must be a hadith. The citation is repeated from the Quran. The subject shifts to monotheism, to the book’s preservation, to the claim that Islam is just. Later the same speaker says the Quran was written 114 years ago, then retreats. On the penalty for leaving the religion, a standard formulation is set down. It is not answered. The topic is replaced.

None of this is unusual. It is what the older texts predict once the words have been offered and despised. The New Testament’s account is blunt. The natural man does not receive the things of the Spirit of God, “for they are foolishness unto him: neither can he know them, because they are spiritually discerned.” A veil remains over the minds of those who do not believe. Hearing, they hear not. The gospel, when it is hidden, “is hid to them that are lost.” The inability is not a shortage of explanations. It is the condition of the hearer.

That condition changes what a public argument can do. It does not cancel the duty to state the thing plainly. It does cancel the expectation that another hour of the same words will open an ear that has already closed. The servant is told to instruct in meekness those who oppose themselves, if God perhaps will give them repentance. The “if” is the whole sentence. Instruction is the speaker’s part. Repentance is not.

American argument likes to treat every refusal as a failure of rhetoric. If the case had been cleaner, the charts better, the tone kinder, the other side would have yielded. Scripture’s picture is less flattering to the speaker and less hopeful about the method. Some hearers are the simple, who lack knowledge and can be taught. Some are scorners. Reprove a scorner and he hates you. Rebuke a wise man and he loves you. The difference is not in the quality of the rebuke. It is in the heart that meets it.

The practical rule that follows is older than any modern debate format. When a house will not receive the messengers or hear their words, they are to leave and shake off the dust. When hearers oppose themselves and blaspheme, the speaker may say that their blood is on their own heads and go elsewhere. After a first and second admonition, a factious man is to be rejected. Of some have compassion. Others save with fear, pulling them out of the fire. Not every refusal is the same refusal. The text that forbids casting pearls also forbids treating every man as a swine.

The danger runs in both directions. Endless argument with a despiser does not usually produce a convert. It produces a speaker who begins to answer a fool according to his folly and becomes like him. It also cheapens the thing being offered. A pearl handled as a prop in a quarrel is no longer quite a pearl. The warning is as much about the honor of the holy thing as about the safety of the speaker.

None of this is an argument for silence in public. The same book that says not to cast pearls says to preach to every creature, to be ready with an answer, and to let speech be gracious and seasoned. The first offering is general. The limit arrives after the offering has been trampled. A man may state, once and clearly, that the male share is double the female share, that the text says so, and that this sits uneasily with equal standing before the law. He is not required to spend the evening proving that the sentence is a sentence.

The harder admission is that the deadlock is not mainly intellectual. People who know God and refuse to glorify him become vain in their imaginations, and their foolish heart is darkened. Professing themselves wise, they become fools. The light shines in darkness, and the darkness does not comprehend it. A debate can display that. It cannot repeal it.

What remains is a modest use of speech. Say the thing. Say it without strutting. Notice when it is being despised rather than weighed. Then stop. The stop is not contempt for the person. It is respect for the difference between an ear that can hear and an ear that will not, and for the old instruction not to spend what is holy where it will only be trodden underfoot.