Logical ReasoningDifficulty: Hard

PT4 S4 Q13 Explanation

Physician: The patient is suffering

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

TopicsPrinciple-Conform

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Stimulus

Physician: The patient is suffering either from disease X or else from disease Y, but there is no available test for distinguishing X from Y. Therefore, since there is an effective treatment for Y but no treatment for X, the patient has a case of Y.

What this question is testing

Principle-Conform

Reasoning

The physician faces a choice: it is X or Y, no test can tell, treatment exists only for Y. If it is X, nothing works — game over. If it is Y, treatment works. So the only scenario where any action helps the patient is the Y scenario. The physician proceeds on that assumption.

Evaluate

This is a classic move. Imagine you are stuck in a remote area and you might or might not have cell service. You cannot test it without trying. If you have service, calling for help works. If you do not, nothing you do with the phone matters. So you act as if you have service — because it is your only path to a good outcome.

Goal

Find the principle that captures this: when success depends on an uncontrollable circumstance being favorable, act as if it is favorable.

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

The question
13.

The physician’s reasoning could be based on which one of the

Answer choices

  1. Bad Description12% picked this

    In treating a patient who has one or the other of two diseases, it is more important to treat the diseases than to determine

    This says treating the disease matters more than diagnosing it. The physician's reasoning is not about ranking treatment over diagnosis — diagnosis is impossible here, not deprioritized. The physician is choosing among treatment strategies based on which scenario allows for success, not arguing that diagnosis is unimportant.

  2. Opposite1% picked this

    If circumstances beyond a decision maker’s control will affect the outcome of the decision maker’s actions, the decision maker must

    This is the reverse of the physician's logic. The physician assumes the favorable circumstance (it is Y, which is treatable). This principle says assume the unfavorable. If the physician followed this, they would assume it is X (untreatable) and not even attempt treatment — the opposite move.

  3. Bad Description11% picked this

    When the soundness of a strategy depends on the truth of a certain assumption, the first step in putting the strategy into effect must

    This says test the assumption first. But the physician's situation is precisely that no test is available — testing is impossible. So this principle does not match. The physician must act without testing, which is the opposite of what this principle prescribes.

  4. Correct55% picked this

    When success is possible only if a circumstance beyond one’s control is favorable, then one’s strategy must be based on the assumption that

    Why this is right

    This nails the physician's reasoning. Success (curing the patient) is only possible if it is Y — that is, only if the uncontrollable circumstance (which disease the patient has) is favorable. The physician's strategy is then based on the assumption that this circumstance is favorable: treat as if it is Y. Apply the principle, and the physician's reasoning falls out as a direct application.

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

  5. Bad Description21% picked this

    When only one strategy carries the possibility of success, circumstances must as much as possible be changed

    This says change circumstances to fit the strategy. The physician cannot change which disease the patient has — the circumstance is fixed and unknowable. The principle the physician is following is to act as if the circumstance is favorable, not to alter the circumstance.

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