Flaws in LSAT Logical Reasoning: Appeal to Authority

    LSAT Prep

    [Read Part 1 , Part 2 , Part 3 , Part 4 Part 5 , Part 6 , and Part 7 of this series here.] 

    Before we continue with Part Eight of our examination of common flaws found in LR questions on the LSAT, let’s once again take a brief moment to review why it’s so important to understand these argumentative errors. Here’s how I began the first post in this series, where we looked at Source Arguments:

    Considering the vast majority of LSAT Logical Reasoning questions will have an argument in their stimulus, and the vast majority of those arguments will contain some sort of flawed reasoning, I thought I would take a moment to address a variety of the flaws that tend to appear with some frequency. In a series of posts I’ll examine a number of common mistakes that authors on the test make, which should prove useful for both Flaw in the Reasoning questions (a type that accounts for about 15% of all LR questions), as well as other question types that require you to respond to argumentation.

    With that in mind, let’s turn our attention to another type of mistake that LSAT authors make, and one that has some real-world applicability, as well: Appeal to Authority. I suppose this could just as easily be titled, “Appeal to Improper Authority,” as this error occurs when an argument is based on evidence provided by someone who could be considered a person of authority/expertise on a subject, or in a field, that is not necessarily related to the subject in the conclusion. In other words, just because someone is an expert regarding one particular topic, does not necessarily qualify that person to speak with authority on other topics.


    Let’s take a look at an example:              

    “World-renowned physicist Dr. Patricia Mitchell assures me that exposure to natural sunlight, even exposure resulting in mild sunburn, is still significantly less of a cancer risk than brief exposure to the artificial light in a tanning bed. So I make sure to tell all of my friends that if they’re looking to get a tan this summer they should do it outdoors, and not at the tanning salon!”

    Granted, we could probably point out a number of errors here, but perhaps the most glaring is that the author concludes that tanning outdoors is preferable to tanning in a salon based on the opinion of a physicist (mathematician specializing in physics), when there is no reason to believe a physicist would have particularly compelling or relevant insights into biological processes such as cancer development. Were the doctor a dermatologist (skin doctor), or even a medical doctor in general, perhaps the expertise of that field would be applicable and persuasive, but a doctor of physics cannot be presumed to be an authority in a field far removed from her area of achievement.


    Here’s how this type of error would likely be represented in an answer choice:

    “the judgment of experts is applied to a matter in which their expertise is not relevant”

    “the argument improperly appeals to the authority of the supervisor”

    “bases a conclusion solely on the authority of the claimant, without seeking further proof”


    Two final points to consider regarding Appeal to Authority errors:

    1. On rare occasions a conclusion will be based on the authority of a person or group whose expertise does seem to apply to the subject at hand, however another person or group with equally relevant authority will offer contradictory evidence or claims. In this case the Appeal to Authority error still exists, but instead of appealing to an improper authority, instead the author makes the mistake of discounting one authority in favor of another, when there is no clear indication of which authority should be considered correct. Two equally authoritative sources with contradictory views simply indicate that a strong conclusion in either direction is questionable.

    2. In instances where multiple authorities are sited, the test makers won’t test your ability to determine degrees of authority or relevant knowledge; for instance, in the tanning example above they wouldn’t have a dermatologist (skin doctor) argue for tanning beds and an oncologist (cancer doctor) argue for sunlight, and then force you to decide which is more reliable authority on skin cancer.

    So on test day be sure to keep an eye out for any argument that draws a conclusion based on the opinions of an authoritative source or so-called “expert.” Just because someone is a reliable authority in one particular field does not necessarily mean that expertise will be relevant to other fields.


    Be sure to review the other posts addressing a wide variety of common flaws you are likely to encounter on test day. Commit them all to memory and you’ll find yourself well prepared to respond to nearly any argument you come across.