Making sure your sentences are inherently logical is one of the most important steps in becoming a good writer. You can be quite meticulous in crafting the grammar and punctuation of your sentences and very careful with your spelling and word usage, but if your material has errors in logic, all your hard work will have been for nothing. Lapses in logic can take several different forms. Some are instantly recognizable in a sentence, while others are a little more subtle and, thus, a little more dangerous. Don't let these errors sneak up on you.

Asking the Impossible: Faulty Predication

Faulty predication (also called illogical predication or — are you ready for this one? — selectional restriction violation) is one type of illogical writing. The term faulty predication means that your subject and verb don't make sense together — that is, the subject can't “be” or “do” the verb.

Take a look at these sentences:

Each of these sentences has an example of faulty predication. Obviously, a breath mint is incapable of assuring anybody of anything; a class isn't when anything; playing the net isn't where anything; and a reason isn't because anything. Each of these sentences needs to be reworded, perhaps like this:

To check for faulty predication, ask yourself if it's possible for each subject to “do” or “be” the verb. If it's not possible, then change your wording.

A Doesn't Follow B: Faulty Coordination

Faulty coordination occurs if you join (combine or coordinate) two clauses in an illogical way:

The word yet (the word that joins, combines, or coordinates the two clauses) is used incorrectly. The sentence could read:

Another example of faulty coordination comes in sentences that contain independent clauses of unequal importance. The sentences are written in a way that makes the clauses seem equal, as in the following sentence:

The cost of the car is much more important than the fact that it has tinted glass (at least, it is to most people). To correct the problem, you could make the second clause subordinate to the first (making the second clause an adjective clause).

Absolutely — Not!

One common problem with comparison occurs when you use absolute adjectives, which are words that — by their definition — can't be compared. Therefore, be sure not to use more, most, quite, rather, somewhat, very, and other qualifiers in front of them.

Round, for instance, is one of those words. Something is either round or it's not. Since one thing can't be rounder than something else, round is an absolute adjective. Other absolute adjectives include: blank, pure, complete, square, dead, straight, empty, true, eternal, and favorite.

Look at these examples:

You can't have a paper that is somewhat blank; either it has something on it or it doesn't.

Because favorite means “at the top of my list,” one place can't be more favorite than someplace else.

Putting Apples with Oranges: Faulty Comparisons

Another problem with faulty comparison occurs if you compare two unlike people, places, or things:

This sentence compares mishaps to May, which makes no sense. The sentence should be rewritten like this:

Take a look at this one:

Here people are being compared to a city — obviously, an illogical comparison. The sentence needs to be reworded, perhaps like this:

Still another problem is an ambiguous comparison, which occurs if you write a statement that could be interpreted two different ways. Look at this sentence:

This is an ambiguous comparison because readers aren't sure what the word more applies to. Does Dawn dislike traveling alone more than she dislikes Dave, or does she dislike traveling more than Dave does?

Let's Not Be Hasty! Sweeping Generalizations

Sweeping (hasty) generalizations use all-encompassing words like anyone, everyone, always, never, everything, all, only, and none, and superlatives like best, greatest, most, least.

Be careful with sentences with generalizations like this one. What happens to the writer's credibility if the country does, in fact, recover from a downturn in six months? You're far better off to write in terms of what happens most of the time than in terms of what always or never happens (not to mention that you're protected when you make a mistake). One rewording of the example is this:

Here's another example of a sweeping generalization:

Everyone? Surely a newborn baby or someone who's recovering from surgery shouldn't strenuously exercise. If you reword the sentence, you can leave some room for exceptions or for debate. Here's a rewording that is more reasonable:

I Don't Follow You: Non Sequiturs

A non sequitur is a problem in logic that states an effect that doesn't follow its cause. Put another way, in a non sequitur, the inference or conclusion that you assert doesn't logically follow from what you previously stated.

As any teacher can tell you, the fact that you turned in a paper doesn't necessarily mean you'll pass the class. What if the paper is (a) not on the assigned topic? (b) too short or too long? (c) plagiarized? (d) three weeks late? (e) written on a kindergarten level? In other words, just because one thing happened, the other doesn't necessarily follow. Here are other examples of non sequiturs:

The Missing Link: Omitted Words

Another frequent mistake in logic is to omit else or other in sentences with comparisons. Read this sentence:

The way the sentence is written, Louise isn't in the family. The sentence needs to be reworded this way:

Sometimes sentences need than or as in order to be logical:

Taking out the phrase if not better than leaves Brent said he could play the guitar as well Jessie, a sentence that's obviously incomplete. The sentence should be written with the extra as to complete the phrase:

Without Rhyme or Reason: Additional Lapses in Logic

Another type of illogical writing to check for is commonly called post hoc, ergo propter hoc, which translates as after this, so because of this (also called coincidental correlation). Here the assumption is that because one thing follows another, the first caused the second.

The second event wasn't caused by the first: the rain wasn't caused by the car being washed (although, come to think of it, it does seem to rain every time you wash your car, doesn't it?).

If you use a false dilemma (an either/or fallacy), you state that only two alternatives exist, when there are actually more than two.

Whitney Becker has other choices: she could call a cab, take the bus, or ask a friend for a ride, so she isn't limited to only two ways of getting to her appointment. If your argument has a red herring, then it dodges the real issue by citing an irrelevant concern as evidence.

The writer or speaker did something wrong; the fact that the driver ahead did something worse is irrelevant.

If you're guilty of circular reasoning, then your writing has what its name implies — reasoning that goes around in a circle, with nothing substantial in the middle. Here's an example:

That sentence has no insight because the writer gives no clarification in the second part about why the epidemic was dangerous; the fact that everyone felt unsafe and at risk doesn't explain the danger.