Logical Fallacies


A fallacy is an error in reasoning, so obviously you need to AVOID these in your persuasive writing.


Hasty generalization – This is making a generalization based on insufficient evidence instead of a great deal of evidence.  “This class is too hard,” said a student after the first assignment.

Overgeneralization – This occurs when a statement is too broad.  It often contains absolute words like all, every, always, everyone, never, no one, none, etc.  “Nobody is here today,” said someone who was here today.

Stereotype – This is a belief that all members of a particular group share certain characteristics just because they are members of the group.  “Rottweilers are killers.”

Cause-and-effect fallacy – Also called post hoc, ergo propter hoc, or “after this, therefore, because of this,” this is making the assumption that one event was caused by a previous one rather than using evidence.  Carrying a rabbit’s foot causes good luck.

Only cause fallacy – This is claiming that a complex situation has one cause.  The only reason students fail is because of a lack of sleep.

False analogy – Analogies or comparisons between two similar things are good.  However, when you use a weak one or a far-fetched one, it weakens your argument. Comparing writing a paragraph to an apple (?)

Ad hominem or Attacking the person – This involves attacking the person when you can’t or haven’t defeated their views.  “You’re ugly and your momma dresses you funny.”

Either-or fallacy or “black and white thinking” --This consists of limiting the possibilities to only two when there are actually more.  “It’s my way or the highway” instead of a compromise.

Non sequitur –This means, “it does not follow” in Latin and targets a conclusion that has no logical premise. “She is good-looking; therefore, she is nice.”

Circular reasoning – This is not giving reasons to back up your opinion and only restating the premise to make it look like you are.  “I am wonderful because I am fantastic.”

Begging the question –This is assuming that your audience accepts the opinion on which the question is based as the truth.  “Are you still beating your wife?”

Bare assertion -- This is stating that there is no argument and that “this is just the way it is.”

Oversimplification – Some things just can’t be simplified, and trying to do so ignores a portion of the issue.  “The trouble with America is a lack of respect.”

Red herring – Just as dragging a stinking smoked fish across a trail can throw a dog off a trail, so can throwing out an idea that really has little or nothing to do with the issue at hand. (The tangents you get your teachers on so you can get out of work.)

Misuse of humor – This involves using humor to cloud the issue or to attack someone. 

Appeal to force – This involves stating that since your argument is held by the majority it must be right and implies that even if it’s not, the majority will rule anyway.  The majority can be wrong.

Irrelevant appeals to authority – The authority you use to back up your claims must actually be an authority on the subject you’re discussing or they aren’t much use.  Using Dr. Seuss to sell arthritis cream.

Appeal to popular sentiment –This is associating your argument with virtues that are popular when there is no real connection (baseball, hot dogs, apple pie, and Chevrolet.”

Appeal to pity – This involves tugging on one’s heartstrings instead of using logical reasons.  Girls squirt tears to get out of tickets.

Appeal to tradition -- This happens when someone refuses to take a fresh look an idea or event and believes it simply because it has always been done that way.  Santa.  The Easter Bunny.

Hypothesis contrary to fact  --This is speculating on what would have happened under other circumstance and cannot be proven.  “If I had turned in all my work, I would have made an A.”

Obfuscation – This is “fuzzy language” often full of technical jargon or big words that in the end means little or nothing.

Ambiguity – When there are two or more possible meanings of a word or statement, the audience has to discover which one is being used.  This is sometimes used to cloud an issue.

Slanted language -- This is using words that, intentionally or not, have a strong negative or positive connotation or feeling associated with them.  Bertrand Russell gives this example:  “I am firm.  You are obstinate.  He is pigheaded.”  All are synonyms and potentially accurate, but one is meant to be an insult.  At Parent Teacher Conferences, teachers say, “Johnny finds the work challenging” instead of “Johnny hasn’t made a grade higher than a 7% all quarter.”

Composition and division -- These two fallacies have the same principle: the parts will have the same qualities as the whole or vice versa.  For example, if the choir is excellent, then each member will be excellent or vice versa.

Contradiction – This occurs when someone changes their position in mid-argument.

Rationalizing – This occurs when a person attempts to justify an action or idea with a believable reason that isn’t the real one.  “I don’t want a Corvette because they suck gas and would raise my insurance.