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You are here: Home / Logical Reasoning / Flaws in Logical Reasoning Part VII: Internal Contradiction

May 20, 2019

Flaws in Logical Reasoning Part VII: Internal Contradiction

Flaws in Logical Reasoning Part 7

Part 7 is here! But before we get going on the topic of internal contradiction, let’s start with a review the importance of this series Take a look at how I began the first post, where we looked at Source Arguments.

The majority of LSAT Logical Reasoning questions have an argument in their stimulus and most will contain some sort of flawed reasoning. In this series, we will address a variety of the flaws that tend to appear with some frequency. I’ll examine common mistakes that authors on the test make. This should prove useful for Flaw in the Reasoning questions (which account for about 15% of LR questions.) It should also help with other question types that require you to respond to argumentation.

Now, how about we move onto another mistake LSAT authors make, one I feel is among the easiest to spot on the test.

Internal Contradiction

This mistake is also sometimes called a “self-contradiction.” It occurs when an author’s conclusion is actually opposite the conclusion that is best supported by the given premises. In other words, an author will provide evidence that contradicts the very conclusion he or she then draws. Like many errors we have reviewed, this can be a confusing notion to grasp in the abstract. So, let’s look at an example of how this specific error might appear.

Mayor: During my previous term, my staff and I spent a great deal of time focusing on our city’s economy. As a result, unemployment reached an all-time high. Clearly you should support my re-election campaign if you are among those still looking for a job.

Attentive reading should make the mistake in the mayor’s argument immediately apparent. If unemployment during his last term reached an all-time high, then a greater percentage of citizens are without jobs. Hence, it is completely illogical to conclude that the unemployed would desire his re-election for economic reasons. The evidence here is in direct opposition to the mayor’s conclusion, and thus an Internal Contradiction error has been committed.

On the LSAT

Here’s how Internal Contradiction would likely be represented in an answer choice.

  • “the author makes irreconcilable presuppositions”
  • “bases a conclusion on claims that are inconsistent with one another”
  • “introduces information that actually contradicts the conclusion”

 A few final points to make about Internal Contradiction errors:

  1. This error tests how closely you are reading and how conscientious you are of specific details provided in the stimulus. Most test takers are conditioned to intuitively attempt to make sense of the information they encounter. This type of mistake often goes unnoticed as people subconsciously ignore or correct the conflicting ideas. The lesson? Read closely! In the example above, replace the word “high” with “low” and the argument makes sense. Many other instances of contradiction are equally as subtle or brief. One word can be the difference in a sound argument and an argument that is entirely self-contradictory.
  2. The idea of “self-contradiction” sounds to many people like “makes a mistake,” or “is in error.” Answer choices like the ones above are commonly presented as traps following stimuli with other, specific reasoning errors. You’ll see the flaw described as “information contradicts the conclusion” more often than you’ll see this mistake appear in the stimulus. People pick this answer choice because they don’t truly know what it means. Or, they assume it suggests the author’s argument is not entirely valid. Don’t fall victim to that trap! Only if you see the specific type of error discussed above—the evidence given would make an opposite conclusion seem likely—should you choose an answer choice that suggests an internal contradiction.

On test day, keep an eye out for any argument that’s conclusion depends on conflicting or contradicting information. Only then do you have an Internal Contradiction flaw and you can quickly search for an answer choice like those presented above.

[Further Reading in Flaws in Logical Reasoning: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10]

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Posted by Jon Denning / Logical Reasoning, LSAT Prep / Logical Reasoning, LR Flaws, LSAT Prep Leave a Comment

  • Rashida C
    January 24, 2015 at 2:46pm

    Jon.
    Thank you for the tips. I find them to be very helpful. I however have a question. Which of the answer choice above is most suitable in this case? I know you listed them as possibilities that the LSAT test makers may use in an answer choice. But if I was force to pick one, which would be the most appropriate considering the argument flaw presented in the stimulus?
    Thanks so much.

  • Jon Denning
    January 27, 2015 at 1:52am

    Hey Rashida – thanks for the comments and I’m really happy to hear you found the posts helpful! What the answer choice indicates is fairly predictable, although the wording is less so and context certainly will factor in. That is, you can trust that somewhere in the correct answer the test makers will discuss the fact that ideas are incompatible, inconsistent, contradictory, irreconcilable, or some other synonymous notion of things that shouldn’t logically coexist. That part is predictable. The specific words chosen are at the test makers’ discretion, however, and may also depend on the subject matter discussed, so I can’t really answer you on likelihood of one particular phrasing appearing. Just trust that if you see an internal contradiction, you can expect an answer that describes an argument that is based on logically conflicting information. I hope that helps!

About Jon Denning

Jon Denning is PowerScore's Vice President and oversees product creation and instructor training for all of the exam services PowerScore offers. He is also a Senior Instructor with 99th percentile scores on the LSAT, GMAT, GRE, SAT, and ACT.

Jon is widely regarded as one of the world's foremost authorities on LSAT preparation, and for the past decade has assisted thousands of students in the law school admissions process. He has also created/co-created a number of PowerScore’s LSAT courses and publications, including the Reading Comprehension Bible, the In Person, Live Online, and On Demand LSAT Courses, the Advanced Logic Games Course, the Advanced Logical Reasoning Course, and a number of books in PowerScore’s popular LSAT Deconstructed Series.

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