Fallacies of Logos

Recognizing a Manipulative Appeal to Logos

Diagramming the argument can help you determine if an appeal to Logos is manipulative. Are the premises true? Does the conclusion follow logically from the premises? Is there sufficient, typical, accurate, and relevant evidence to support inductive reasoning? Is the speaker or author attempting to divert your attention from the real issues? These are some of the elements you might consider while evaluating an argument for the use of logos.

Pay particular attention to numbers, statistics, findings, and quotes used to support an argument. Be critical of the source and do your own investigation of the "facts."

Fallacies that Appeal to Logos

Hasty generalization: jumping to conclusions based upon an unrepresentative sample or insufficient evidence.

Example: "10 of the last 14 National Spelling Bee Champions have been Indian American. Indian Americans must all be great spellers!"

Appeal to ignorance—true believer's form: arguing along the lines that if an opponent can't prove something isn't the case, then it is reasonable to believe that it is the case; transfers the burden of proof away from the person making the claim (the proponent).

Example: "You can't prove that extraterrestrials haven't visited earth, so it is reasonable to believe that they have visited earth."

Appeal to ignorance—skeptic's form: confusing absence of evidence with evidence of absence; assumes that if you cannot now prove something exists, then it is shown that it doesn't exist.

Example: "There's no proof that starting classes later in the day will improve the performance of our high school students; therefore, this change in schedule will not work."

Begging the question: circular argument because the premise is the same as the claim that you are trying to prove.

Example: "This legislation is sinful because it is the wrong thing to do."

False dilemma: misuse of the either/or argument; presenting only two options when other choices exist

Example: "Either we pass this ordinance or there will be rioting in the streets."

Post hoc ergo propter hoc: Latin phrase meaning "after this, therefore because of this"; confuses correlation with causation by concluding that an event preceding a second event must be the cause of that second event.

Example: "My child was diagnosed with autism after receiving vaccinations. That is proof that vaccines are to blame."

Non-sequitur: Latin for "does not follow"; the conclusion cannot be inferred from the premises because there is a break in the logical connection between a claim and the premises that are meant to support it, either because a premise is untrue (or missing) or because the relationship between premises does not support the deduction stated in the claim.

Example (untrue premise):"If she is a Radford student, she is a member of a sorority. She is a Radford student. Therefore she is a member of a sorority."

Smoke screen: avoiding the real issue or a tough question by introducing an unrelated topic as a distraction; sometimes called a red herring.

Example: "My opponent says I am weak on crime, but I have been one of the most reliable participants in city council meetings."

Straw man: pretending to criticize an opponent's position but actually misrepresenting his or her view as simpler and/or more extreme than it is and therefore easier to refute than the original or actual position; unfairly undermines credibility of claim if not source of claim.

Example: "Senator Smith says we should cut back the Defense budget. His position is that we should let down our defenses and just trust our enemies not to attack us!"