Avoid Logical Fallacies

Hasty generalization — a conclusion based on insufficient or unrepresentative evidence.
Deaths from drug overdoses in Fremont have doubled in the past three years. Therefore, more Americans than ever are dying from drug abuse.

Many hasty generalizations contain words like all, every, always and never, when qualifiers such as most, many, usually and seldom would be more accurate. Either have enough data to verify your statements or use qualifiers.

Non Sequitur (Latin for “does not follow”) — a conclusion that does not follow logically from preceding statements or that is based on irrelevant data.

Mary loves food; therefore she will be an excellent chef.  Mary’s love of food is no guarantee she will be able to cook.

False Analogy — falsely assumes that because two things are alike in one respect, they must be alike in others.
If we can put a man on the moon, we should be able to find a cure for the common cold. Both are scientific challenges, but quite different.

Either... Or Fallacy — the suggestion that only two alternatives exist when if fact there are more.
Either the 49ers find a new running back, or they will never make it to the Super Bowl..
Actually, the team could make it to the Super Bowl without a new running back.

Faulty Cause-And-Effect Reasoning — assuming that because one event follows another, the first is the cause of the second. Like a non sequitur, it is a leap to an unjustified conclusion.

Since Gov. Smith took office, unemployment in the state has decreased by 7 percent. Gov. Smith should be applauded for reducing unemployment.

We must show Gov. Smith’s policies caused the decrease.

Circular Reasoning — instead of supporting the conclusion with evidence, the writer simply restates the conclusion in different language.

Faculty and administrators should not be permitted to come to student council meetings because student council meetings should be for students only.

The writer has not explained the position, but has merely repeated the point.