Logical ReasoningDifficulty: Easy

PT106 S1 Q4 Explanation

Dental researcher: Filling a cavity

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsPrinciple-Strengthen

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Stimulus

Dental researcher: Filling a cavity in a tooth is not a harmless procedure: it inevitably damages some of the healthy parts of the tooth. Cavities are harmful only if the decay reaches the nerves inside the tooth, and many cavities, if left untreated, never progress to that point. Therefore, inside the tooth are in imminent danger from that cavity.

What this question is testing

Principle-Strengthen

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
4.

Which one of the following principles, if valid, most strongly supports the

Answer choices

  1. Bad Conclusion Match9% picked this

    Dentists should perform any procedure that is likely to be beneficial in the long term, but only if the procedure

    As soon as we see this rule would tell a dentist that they should perform a procedure, we know it's a bad match for justifying our conclusion, which is saying that a dentist shouldn't perform a procedure. This rule is saying, If procedure is likely to be beneficial long-term dentist should and → perform the doesn't cause immediate procedure damage

  2. Bad Conclusion Match2% picked this

    Dentists should help their patients to prevent cavities rather than waiting until cavities are present

    As soon as we see this rule would tell a dentist that they should help patients prevent, we know it's a bad match for justifying our conclusion, which is saying that a dentist shouldn't perform a procedure.

  3. Correct85% picked this

    A condition that is only potentially harmful should not be treated using a method that

    Why this is right

    This is saying if condition is only → should not be treated w/ potentially harmful method that's def harmful The conclusion is talking about situations in which the nerves are not in imminent danger from a cavity. Is a cavity that's not imminently threatening nerves a condition that is "only potentially harmful"? Sure, it said that "many cavities never progress to the point of reaching the nerves inside the tooth, and thus that many cavities are not harmful". Is filling a cavity "a method that is definitely harmful"? Yes, we're told that filling a cavity "inevitably damages some of the healthy parts of the tooth". So this rule applies to cavities that haven't reached the nerve and applies to the method of filling cavities, and it counsels us that we shouldn't use the method of filling cavities when we have the condition of an only potentially harmful cavity, which matches our conclusion.

    Skill tested: Principle-Strengthen · how this choice captures the argument's function is the move to repeat next time.

  4. Bad Evidence/Conclusion Match1% picked this

    A condition that is typically progressive should not be treated using methods that provide

    Can we say that having a cavity is a condition that is "typically progressive"? No, we don't know whether cavities usually / typically / most of the time progress. Can we call filling cavities a method that "provides only temporary relief"? No, the paragraph never said that the relief provided by filling a cavity eventually goes away.

  5. Bad Conclusion Match3% picked this

    A condition that is potentially harmful should not be left untreated unless it can be

    As soon as we see this rule would say we should not leave a cavity untreated, we know it's a bad match for justifying our conclusion, which is saying that a dentist shouldn't treat the cavity. This answer says If a potentially harmful then the condition condition can't be kept → should be under constant surveillance treated

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