Fallacies

How to avoid errors in logic

Fallacies Defined

Statements that may sound true but are deceptive and dishonest.

Deal directly with the issue

Don’t disguise emotion for logic. Appealing to emotion is only okay if

both the reader and the author understand the appeal is to emotion rather than logic. Can the appeal to emotion tie in with your logical reasoning?

Non Sequitur

Statements that do not follow logically from the previous statement.

As a militant feminist, Emma was doomed to disappointment in her love life.

Avoid abstract ideas and circular reasoning

Appealing to an abstraction is not logical.

Common sense tells us idealists cannot be great leaders.

Avoid circular reasoning. I feel sympathy for her because I

identify with her.

Identify generalizations

Sweeping generalizations are overly broad. Men make poor proofreaders because they

don’t pay attention to details. Hasty generalizations are made after

examining too few pieces of evidence. My sister’s experience with smoking shows

me that smokers can quit anytime they want.

Use credible authorities

Don’t use an authority in a place where his or expertise does not apply.

Because Suzanne Sommers was an actress, she knows the best way to get tight abs.

Avoid false analogies. If we can create sophisticated computers,

we should be able to cure cancer.

Use logical reasoning Avoid gaps in cause and effect

reasoning. Post hoc, ergo propter hoc (After this, therefore because of this

Of course, Ella flunked her English course. Just last month, she started hanging out with smokers.

My neighbor’s power went out when I dried my hair. If I use my hair dryer again, my neighbor won’t have power.

Use logical reasoning

Avoid either-or reasoning when more than one option exists. False Dilemma

Overcrowded prisons have left us with two alternatives: let criminals loose on the street or make capital punishment a real threat.

Avoid personal attacks

Argument ad hominem: An attempt to divert attention from the facts by attacking motive or character.

Don’t listen to his argument against raising tuition; he’s a high school dropout who drinks every night.

Avoid logical fallacies

Deal directly with issues. Make sure your evidence is sound and

related to the issue. Check your reasoning for embarrassing

gaps. Identify generalizations and make sure

they are sound.