Flaws in LSAT Logical Reasoning: Uncertain Use of a Term

    LSAT Prep

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

    Before we continue with Part Six 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 seems to confound a number of students on the actual test: Uncertain Use of a Term or Concept. This particular mistake violates an argumentative principle to which authors must adhere—as an argument progresses, each term and concept discussed must be used in a consistent, coherent fashion. If an author uses some term, or discusses some concept, in different ways in making her argument, then the argument itself becomes inherently confusing and its integrity is fundamentally undermined.

    Because this can be a somewhat confusing notion to grasp in the abstract, let’s look at an example of how this specific error might appear:

    Board Member: “If this company is going to maximize its profits in the coming year, we need to fully exploit all of our available resources.”

    Human Resources Director: “Not so fast. Our employees are one of our most valued resources, and we have a strict policy against exploiting our workers.”

    Think about what’s wrong with the HR Director’s response. While it is certainly true that employees are a resource and policies exist to protect them from exploitation, is that the same use of the word “exploit” that the Board Member intends? No, of course not. The Board Member simply means “capitalize on available opportunities to maximize profits,” whereas the HR Director interprets (incorrectly) “exploit” to mean “take advantage of in a malicious or harmful way.” Hence her response fails to address the argument made by the Board Member and is flawed as a result.

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

    “depending on the ambiguous use of a key term”

    “equivocates with respect to a central concept”

    “it confuses two different meanings of the word ‘exploit’”


    So on test day be sure to keep an eye out for any argument that uses a word or idea more than once and in an inconsistent fashion. Any time an author relies on a shifting or misconstrued meaning, then the argument contains an Uncertain Use flaw and you can quickly search for an answer choice like those presented above.

    A final point about this error: because most test takers don’t really understand how this particular mistake works, answer choices like the ones above are very commonly presented as traps following stimuli with other reasoning errors. That is, you’ll see “uncertain use” or “equivocation” described as the flaw much more often than you’ll see this type of mistake actually appear in the stimulus. People pick this answer choice because they don’t truly know what it means, but don’t fall victim to that trap! Only if you see the specific type of error discussed above should you choose an answer choice that suggests uncertain usage.


    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.