How to Attack Flaw in the Reasoning Questions on the LSAT

Flaw in the Reasoning questions require you to identify the underlying logical flaw in the argument. Over time, Flaw questions have become among the most common question types on the Logical Reasoning section of the LSAT. In fact, they account for approximately 15% of all questions and 30% of all First Family questions. Your next test will likely contain as many Flaw questions as all Main Point, Method, Parallel, Parallel Flaw, and Cannot Be True questions combined. 

In many ways, Flaw in the Reasoning questions are just like Method of Reasoning questions. They both represent an attempt to measure your understanding of abstract argument structure and contain answer choices that can be proven or disproven by directly referring to the content in the stimulus. In Flaw questions, however, the question stem indicates that the argument contains flawed reasoning. Since the test makers freely provide this fact, it is essential that you capitalize on this information!  Identify the error of reasoning in the stimulus before proceeding to the answer choices. While this list isn’t comprehensive, it represents many of the most common reasoning errors you’ll run into on the LSAT. 

• Source Arguments, “ad hominem” attacks 
• Circular Reasoning 
• Exceptional Case/Over-generalizations 
• Errors of Composition and Division 
• False Dilemma 
• Uncertain Use of a Term, Error of Equivocation 
• Internal Contradictions 
• Appeal to Authority 
• Appeal to Emotion 
• Time Shift Errors 
• Errors in the Use of Evidence, including survey-based errors 
• “Straw Man” 
• Mistaken Cause and Effect 
• Error of Conditional Reasoning 

Don’t Get Stuck! 

Test-takers often get “stuck” on Flaw questions. This is usually due to one of two reasons. Either you fail to understand the flaw and prephrase improperly or your prephrase did not match any answer choices. The latter problem is easier to fix. This usually shows that you have a good grasp of logical fallacies! But, it’s also clear you didn’t take the time to fully examine the variety of ways they can appear on the test. Alternatively, you may be getting too “boxed in” your prephrase, preventing you from recognizing the correct answer choice even though you know what you are looking for in general. 

On a rare occasion, however, you may have no idea what the flaw in the argument is. If this happens, it’s time for Plan B. If you can understand how to weaken the argument, then fundamentally you have some grasp of the flaw in it. Then you can use that information to help you determine the correct answer choice. If you know a weakness in an argument, you are capable of seeing a concrete way to attack the argument. This reveals, to some extent, the abstract nature of the flaw that is present. 

This works because arguments frequently fail to take into account any number of different possibilities, most of which are entirely irrelevant to the logical validity of the conclusion. A discrete number of possibilities, however, are relevant and should have been taken into account. Why? Because, if true, they could potentially weaken the argument. The author should only consider possibilities that could potentially weaken the argument and whose omissions amounts to a logical flaw!