Eight Problems of Logic in Writing

Persuasive writing avoids these rhetorical flaws

(An excerpt from Stet Again!)

Few things ruin a piece of good writing quicker than a bad argument. The theme may be as clear as distilled water. The words may fit the topic, and the sentences may flow like warm honey. The rhetorical flourishes may all be subtle, and the tone seductive. But if the writer falls into the many logical errors to which all argument is prone, the whole effort is jeopardized.

Here we look at eight logic problems in writing: faulty generalization, false dilemmas, the post hoc ergo propter hoc argument, the ad hominem argument, question begging, the improper appeal to authority, imperfect or false analogies, and the non sequitur. Examples and editorial strategies are suggested for each.

Faulty generalization

This is perhaps the most common error in argument construction. Broad generalizations about difficult and controversial topics seldom stand scrutiny; hence, one useful rule of thumb for editors is: The stronger the generalization, the more bells should go off in the editor's mind.

Fortunately, faulty generalizations give off powerful signals. Often they are preceded by absolute words like all, always, anyone, every(one)(thing), only, never, and none. Frequently they are flagged by superlatives: best, greatest, most, least. The recommended editorial treatment is to qualify the absolutes and superlatives.

Example and strategy: "Hamlet is the best play ever written in English" can be easily changed to "Many scholars agree that Hamlet is one of the best plays..." once the author agrees.

False dilemma

This error usually takes the form of presenting two (or three) alternatives as if they were mutually exclusive, when they are really just the obvious options or the ones the writer finds easiest to manipulate. The words and phrases that commonly signal false dilemmas are these: either...or; the only alternative/possibility/choice is; since X is obviously false/has not worked, Y is clearly true/our only choice. The recommended treatment is to break open the dilemma by broadening the statement or, where called for, the entire argument.

Example and strategy: "Either the courts or the individual conscience is entitled to speak on abortion, but not both." Here, the editor must point out the logical problems created by the implication that there are only two possible camps to be in. It is well within the realm of logic for both conscience and courts to speak, for example. Or the dilemma can be broken open by querying the role of the church and other moral leaders.

Post hoc ergo propter hoc

This error is among the most common fallacies of thinking and therefore of writing. The Latin phrase means "after this, therefore on account of this." The error lies in assuming that establishing a chronological relationship automatically establishes a causal one. Some of the key signals to look for, of course, are words that highlight conclusory statements: therefore, thus, consequently, as a result, accordingly, on account of. But not all post hoc errors are that easy to spot.

Example and strategy: "The period following the U.S. hydrogen bomb tests in the South Pacific was marked by uncharacteristic and dramatic weather changes, directly related to the tests." As the statisticians say, "Correlation is not causality." In the absence of strong evidence to bolster the writer's implication, the statement draws a hidden and unwarranted conclusion and therefore should be qualified, perhaps by inserting some phrase like "leading many meteorological experts to conclude that the changes were..." before the word "directly," followed by the evidence itself.

Argument ad hominem

This logic error substitutes discrediting one's opponent for discrediting the opponent's arguments. The fallacy is sometimes difficult to identify, primarily because the individual involved may be relevant to the issue. For example, the 1947 conviction of James Michael Curley for mail fraud while in office became an issue in his 1949 campaign for reelection as mayor of Boston. But in most cases, the ad hominem argument should not be allowed to stand.

Example and strategy: "Karl Marx's poor performance as a provider for his own family is reason enough to doubt the validity of his social and economic theories." Marx's ability to earn a living may or may not have anything to do with the validity of his theories, which are quite large in scale. The editor must ask the author either to present historical and economic facts discrediting the theories, independent of Marx's performance as a provider, or show that Marx's application of his theories in his own household caused his family economic hardship.

Question begging

Question begging comes in two main forms. One is a form of circular or tautological reasoning. Setting out to make a point, the writer posits the conclusion the reader is expected to make, then supports or "proves" it by some restatement or assertion of the original point. The conclusion gives rise to the reason, which supports the conclusion.

Example and strategy: "The study of history gives excellent insights into human nature because one can learn much about personal character by learning about the events and circumstances of the past." Here, the reason provided for the proposition in the first half of the sentence is simply the proposition's restatement in slightly different words in the second half. The editor needs to flag the error with "Tautol." or "Circ. Arg.," improve the sentence simply by breaking off the last half of it, and follow up by asking the author to give a concrete example.

A second form of question begging is the smuggled assumption. In this case the writer hides an assumption in the statement of a proposition and proceeds to prove or support the proposition by drawing on the hidden assumption.

Example and strategy: "Capital punishment is forbidden in Sweden and its homicide rate is lower than ours. We should therefore abolish capital punishment." The hidden assumption is that the relationship between the absence of capital punishment and Sweden's low homicide rate is a causal one. What should be proven — that we should abolish capital punishment — is supported by this assumption. A useful editorial strategy is to state the question that is, in fact, begged by the offending sentence: "Does lack of capital punishment cause low murder rate? Are there other factors?"

Improper appeals to authority

Appeals to authority are common in all writing: "As Churchill once said...," "Four out of five doctors agree...," "According to the AMA Journal...," "Research shows...." But appeals to authority have different weights, and not all authorities are trustworthy beyond their fields of expertise. Henry Kissinger's statements about Russian cuisine are less authoritative than his statements about Soviet foreign policy.

Nor is the evidence provided by polls necessarily authoritative.

Example and strategy: "Forty-seven percent of New York viewers characterized William Hurt's performance in The Accidental Tourist as his best ever." The editor could pencil in any or all of the following questions in the margin: "What New York viewers?" "What are their qualifications for judging acting?" "What was the size of the sample?" Other questions editors can put to appeals to authority include: "Is this authority competent in this field?" "Is the authority providing evidence, reasoned analysis, or merely opinion to support the argument?" "Is the authority known to have a specific bias?" "Is the authority's statement up-to-date?"

Imperfect or false analogy

Reasoning by analogy attempts to make a case by comparing something known with something not known or not as well known. The potential for error lies in an unwarranted leap of logic: The writer jumps from the fact that two partners in the analogy share one or more characteristics to the assumption that the second partner in the analogy shares an additional characteristic of the first, which characteristic is relevant to the matter at hand. The logical argument of the false analogy has this syllogistic form:

X and Y share characteristics a, b, and c.

X has the further characteristic z.

Therefore, Y must share characteristic z.

Example and strategy: "Education cannot possibly prepare a couple for parenthood. Trying to educate them for such a task is like trying to teach them to swim without putting them in the water; it can't be done." Here the argument assumes a set of shared characteristics between parenthood and swimming — overcoming fears, learning new skills, adapting to a new environment, adopting new behavior patterns, and so forth. But, the editor can point out, swimming and parenthood are also very different from each other. A terse "Analogy doesn't work. Swimming skills physical; parenting skills psychosocial" should wake the author up.

The great value of analogical argument lies in the insight revealed by the unexpected juxtaposition of two elements. But all analogies break down when pressed too far. The trick the editor must learn is to find where the line is and not let the writer cross it.

Non sequiturs

A non sequitur is a conclusion or inference that "does not follow" from the premises offered. Some examples of non sequiturs are

Delton drinks too much. He probably beats his kids, too.

Phogbound is a politician. Can we trust him?

Elyse has perfect Sunday school attendance; I'll bet she's well behaved at home.

Non sequiturs are similar to false analogies in that both depend on the transfer of imputed characteristics from one context to another to make the point. But non sequiturs are more fallacious forms of reasoning than false analogies because the relationships on which they depend are usually more tenuous. There may be a certain "reasonableness" to non sequiturs; for example, Elyse's perfect Sunday school attendance may lead us to think she's a "nice little girl," but there may be another, better reason that explains her behavior (perhaps her parents make her go); she may be a perfect hellion at home. The editor can simply query: "Perfect attendance = good behavior @ home?"

Logic is crucial to sound argument and persuasion, and thus to clear writing. It is, as Jean de la Bruyère has said, "the art of making truth prevail." But logic can also be overdone. Some of our most profound experiences — love of country, romantic passion, religious awe, aesthetic joy — defy logic, and these too must be expressed. The beginning editor will thus slowly learn the lesson taught by Pascal, which experienced editors already know, that "the last function of reason is to know the infinity of things that surpass it."

—Bruce O. Boston

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