Logical Fallacies

Logical fallacies are faults in reasoning. You'll find such fallacies often in advertisements and political speeches, but also in everyday conversations around the lunch table. Perpetrators may misuse evidence, distort ideas, sabotage the discussion, or reach false conclusions. Some arguments contain multiple offenses.

Whenever logical fallacies occur, arguments fall apart. As a result, you should avoid such faults in your own arguments and recognize them in the reasoning of others.

Misused Evidence

Some faulty reasoning comes from misusing evidence—providing false premises or deriving illogical inferences. The most common types of misused evidence appear below.

• An ad hominem attack criticizes the person making the claim rather than the claim itself.

  The representative wants to cut social programs, but what he really needs to cut is his hair.

• A false analogy uses a misleading metaphor, pretending that dissimilar situations are similar.

  Our privately owned company is a rock—completely solid but not going anywhere. A rolling stone gathers no moss, but we are gathering moss because of being private. If we go public, this rock will still be solid, but it'll start rolling, and the moss will fly off. Won't that be a beautiful sight—a moss-free company?

• A half-truth misrepresents a situation by cherry-picking evidence and ignoring part of the story.

  Schools with low-scoring students are failing and should lose their funding, which should be given to schools with high-scoring students.

• If-only thinking argues using a situation that did not occur, and so is pure speculation.

  If only we had bought the laundry detergent I wanted, our washer would not have broken down.

• Impressing with numbers involves dazzling readers with statistics to hide a faulty argument.

  In a recent poll, 20 percent of voters were over 55, and 62 percent of them approved of fewer regulations on the 23 percent of businesses that produced less than 15 percent of carbon emissions.

• Obfuscation uses confusing language and technical terms to hide a weak or controversial argument.

  If we recalibrate the client-vendor coefficient to optimize outsourcing of insourced assets, particularly human resources entitled to complete compensatory packages, we can minimize revenue outputs and maximize inputs.

Distortions

Some arguments distort the issue itself, shutting down discussion. Watch for the following distortions in others' arguments, and avoid them in your own.

• A bare assertion states a position and denies any possibility of discussion.

  Our competition has nothing to offer our customers. I don't want to hear about anything they are marketing. It's all garbage.

• A complex question is a verbal trap that allows no good answer.

  When will you stop trying to destroy the company and face up to the terrible damage you have done?

• Either/or thinking contrasts the arguer's position to an extreme and unacceptable alternative.

  You have a clear choice: Either pass my proposal to revamp the sales force, or go bankrupt.

• An oversimplification represents a complex situation in simplistic terms.

  Our allies are countries with human rights, and our enemies are countries without them.

• The straw-man fallacy sets up an argument that the opposition would never make and then easily knocks it down, much like a straw dummy "defeated" by a medieval knight.

  Don't buy your groceries from a store that wants to sicken its customers. Come to Manny's Market for fresh, healthful foods.

Sabotage

Some arguments go beyond distortions, using illogical means to manipulate their audiences. The most frequent types of sabotage appear below.

• An appeal to pity tries to guilt the person into action.

  When you step on the scale, remember that every extra pound you have is food that could have fed the hungry.

• An appeal to popular sentiment manipulates the person by evoking something beloved.

  Grandmas across America make their sweet pies with Flaky Fanny's Preformed Pie Crusts.

• Bandwagoning argues that everyone else is doing it, so you should, too.

  What do all the happy people have in common? Where do they go three times a week for fun and friendship? How do they get so fit? Simple. Pilates! Come join the cool kids!

• Misuse of humor tries to convince an audience with a joke instead of an argument.

  If your insurance company makes you sweat, hire Jacobson and Hanley. We'll given them a legal workout that'll have them dripping.

• A red herring is a shocking statement that distracts from the real issue. (The term comes from the practice of dragging a fish across a trail to throw off scent dogs.)

  Water is the universal solvent, rusting metal and tearing down mountains. Imagine what it is doing inside your stomach. Calm that stomach with soda.

• Threatening people is what bullies do to get their way.

  If you think our family counseling is expensive, you'll hate paying for your divorce.

False Conclusions

False premises, inferences, or assumptions can result in false conclusions. Incorrect reasoning can as well. In an inductive argument, a conclusion can be false simply because it does not apply to all cases. Watch for these types of false conclusions.

• An appeal to ignorance uses a lack of evidence to argue for a conclusion.

  We haven't been able to figure out why our sales are slumping, so they really must be climbing.

• A broad generalization uses limited evidence to create a sweeping conclusion.

  I've talked to two other salespeople who are concerned about the new catalog. I'm telling you, everybody hates it.

• Circular reasoning uses the conclusion of the argument as a premise.

  I'm not going to give the auditors access to our books. They have very little evidence of wrongdoing. Their case is so slim. They need lots more evidence if they want access. I'm not going to give them the evidence they need.

• A false cause claims that one condition causes another when the two conditions are related only in a time sequence.

  Every time I watch the Packers, they lose. I've stopped watching them so that they can go to the Superbowl.

• A non sequitur is a conclusion that does not follow logically from its premise.

  We have five main departments in the company, so the letterhead has to be maroon.

• The slippery slope fallacy argues that a single step will create a calamitous avalanche of events.

  If we let Jim run home to take care of his sick son, everybody's "son" will suddenly be "sick."