Improving Academic Performance

10 Common Logical Fallacies Found on the LSAT

Written by Mark Skoskiewicz | May 22, 2011 12:35:00 PM Z

Understanding common logical fallacies is critical to LSAT success.

Logical reasoning involves the ability to construct and deconstruct an argument. Across the four scored sections of the LSAT, you can assume that approximately half of the questions you encounter will involve logical reasoning. It is directly tested in the LSAT's logical reasoning section, and since there are two logical reasoning sections, one reading comprehension section, and one analytical reasoning section, all of which have 35 questions, 50% of the LSAT questions you see will involved logical reasoning.

But, wait, there's more to it than even that. The ability to use logic when understanding an argument is also tested indirectly in the reading comprehension section and the writing sample. Because logical reasoning is such a commonly tested skill on the LSAT, quickly identifying and understanding flawed arguments is critical to achieving a high LSAT score.

One way to understand weaknesses of an argument is knowledge of common logical fallacies.

Although the makers of the LSAT are clear that you do not need to memorize the specific terminology related to flawed arguments below, such as "Ad Hominem" or " Ad Populum," it is important to have a deep understanding of concepts like: argument, premise, assumption, and conclusion.

If you are studying for the LSAT you may consider our private LSAT tutoring. However, we also offer a weekly online small group tutoring option for where you submit logical reasoning question and have them explained to you before or during a live online LSAT review session each week.

What follows are descriptions and examples of 10 common logical fallacies, most of which are likely to appear in the logical reasoning section of the LSAT at one point or another.

  1. Ad Hominem: This occurs when an author attacks his opponent instead of his opponent’s argument.
    Example: Trina thinks guns should be outlawed but Trina doesn’t go to church, so we shouldn’t listen to her
  2. Ad Populum: Ad Populum attempts to prove an argument as correct simply because many people believe it to be so.
    Example: 80% of people are for the death penalty, therefore, the death penalty is moral.
  3. Appeal to Authority:  In this fallacious argument, the author claims his argument is right because someone famous or powerful supports it.
    Example: We should change the drinking age because Einstein believed that 18 was the proper drinking age
  4. Begging the Question: This happens when the author’s premise and conclusion say the same thing.
    Example: Fashion magazines don’t hurt women’s self esteem because women’s confidence is intact after reading the magazine.
  5. False Dichotomy: This fallacy rests on the assumption that there are only two possible solutions, so disproving one solution means that other solution should be utilized. It ignores other alternative solutions.Example: The teacher gives too many A’s and therefore must be fired because grade inflation is unfair to other students
  6. Hasty Generalization: Hasty Generalization occurs when the proponent uses too small of a sample size to support a sweeping generalization.Example: Sally couldn’t find any cute clothes at the boutique and neither could Maura, so the boutique doesn’t have any cute clothes.
  7. Post Hoc/ False Cause: This fallacy assumes that correlation equals causation or, in other words, if one event predicts another event it must have also caused the event.Example: The football team gets better grades than the baseball team, therefore playing football makes you smarter than playing baseball.
  8. Missing the Point: In Missing the Point, the premise of the argument supports a specific conclusion but not the one the author draws. Example: Antidepressants are overly prescribed which is dangerous, so they should clearly be made illegal.
  9. Spotlight Fallacy: This occurs when the author assumes that the cases that receive the most publicity are the most common cases.Example: 90% of news reports talk about negative events. Therefore, it follows that 90% of events that occur in the real world are negative.
  10. Straw Man: In this fallacy, the author puts forth one of his opponent’s weaker, less central arguments forward and destroys it, while acting like this argument is the crux of the issue. Example: My opponent wants to increase teachers’ pay but studies have shown that professors with tenure don’t work as hard at their job to improve themselves.

Understanding the common logical fallacies above should help you improve your score on the LSAT. But it could also help you win arguments in real life too. And, let’s face it, winning arguments is fun.
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