(1.) Is there an alternative explanation that is possible? An alternative explanation is a different reason for the same claim. Probing the alternative explanations or reasons for a claim is an excellent way to open up weaknesses in the author's logic.

(3.) What assumptions do the reasons rest on? An assumption is what one takes for granted to be true, but which actually may not be true. All arguments rest on some common assumptions. This common ground makes it possible for two people to have a dialogue in the first place, but these assumptions, because they are based on groundless ideas, make for a "sweet spot" of attack in argument.

• Example: "John was late because his previous class is on the far side of campus." (The assumption is that it takes a long time to get from the far side of campus to class. If John walked the same speed as the one presenting the argument, the assumption would be a shared one. However, it may be the case that John actually walks much faster than assumed, and that he was late for another reason.)

  Either/Or: Narrowing the options to just two extremes when in actuality more options exist. Example: Either John was late because he forgot where the class was, or because he didn't want to come. (Actually, John may have been late for another reason not listed here. Maybe he fell down a manhole.) Example: Either spend the entire night proofreading your paper or you will get an F in the course. (Actually, you might ask the teacher for a one day extension so that you don't have to kill yourself with an all-nighter. The point is that there aren't just two options.)

  Non Sequitar: The conclusion/claim doesn't follow from the reasons. Example: I saw John talking to a pretty girl this morning. Therefore, he is late to class because he's probably eating lunch with her. (It doesn't follow that talking to a pretty girl would lead to a truant luncheon.) Example: Some cars drive recklessly along the roads where pedestrians walk, endangering them. Therefore, we should ban pedestrians from walking down some roads. (It doesn't follow that you should punish the pedestrians instead of the cars.)

  Slippery Slope: Exaggerating the consequences. Example: If John is late to class, he'll miss the material and do poorly on the test. When his father sees his bad grades, John will be whipped and then he'll run away and join the circus. (Actually, John may do fine on the test even though he missed class.) Example: Students who arrive late to class will receive low grades, which will then prevent them from declaring their majors. If students can't declare the majors they want, they'll lead miserable lives fulfilling careers they hate until they finally commit suicide. (Actually, even if students receive a low grade, it doesn't mean they won't be able to bring up their other grades in other classes and still declare the majors they want.)

  Fallacy of Authority: Accepting for truth what is claimed simply because someone said so. Example: John was late to class because his the school psychologist said John was having bouts of depression and may not attend class. (Actually, what the psychologist said may be wrong. Maybe John even lied to her.) Example: John Grisham, an expert in law, says law is a tedious yet exciting practice. So it must be the case that law is a tedious, exciting practice. (Actually, what Grisham says may not be true. He hasn't supplied any reasoning for his assertion, and he's a popular fiction writer rather than a lawyer.)

  Faulty Cause and Effect: Attributing the wrong cause to the effect. Example: John was late to class because he went to the dentist yesterday and had a root canal. (Actually, John may be late for another reason.) Example: The horses are acting strange because there's a deep storm brewing. (Actually, the horses may be acting strange because they're hungry.)

  Hasty Generalization: Generalizing from a sample that is too small. Example: John was late to my physics class all last semester. Therefore John is just an unpunctual, late person. (Actually, last semester John may have had difficulty getting to physics, but no trouble getting to his other classes.) Example: I conclude from the several pleasant, hard-working AUC students I met this morning that all AUC students are pleasant, hard-working students. (Actually, you may have just met the only three nice students on campus.)

  Select a fallacy above to see an explanation of it in this window.

• Hasty Generalization           
• Faulty Cause and Effect
• Fallacy of Authority
• Slippery Slope
• Non Sequitar
• Either/Or

Practice with fallacies