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Difficulty: HardNecessary vs. Sufficient Condition Flaws

The following argument excerpts rely on various patterns of reasoning. Which of the following arguments exhibit a logical flaw wherein a necessary condition is confused with a sufficient condition? Select all that apply.

  1. A symphony is selected for the orchestra's gala season only if it features a prominent brass section. The recently composed 'Autumn Suite' was not selected for the gala season. It follows that the suite must not feature a prominent brass section.Answer
  2. B
    No medication can be approved for widespread distribution unless it passes Phase III clinical trials. The experimental drug Myloxate did not pass its Phase III clinical trials, so it will not be approved for widespread distribution.
  3. Any candidate who secures an executive board position must have at least ten years of industry experience. Mr. Henderson has over fifteen years of industry experience. Therefore, Mr. Henderson will certainly secure an executive board position.Answer
  4. D
    A recent study demonstrated that individuals who regularly consume organic vegetables report higher overall life satisfaction. Consequently, we can conclude that eating organic vegetables significantly improves one's psychological well-being.
  5. E
    The city council argues that the new transit policy is sound because it is based on conservative financial principles. However, the council members themselves are not politically conservative, so their claim about the policy's foundation cannot be true.

Answer

The arguments regarding the symphony selection and the executive board candidate both commit necessary versus sufficient condition flaws.
The correct arguments incorrectly treat conditional requirements as mutual guarantees. The symphony argument commits an illegal negation by assuming that because the sufficient condition (selection) was not met, the necessary condition (brass section) must also be absent. The executive board argument commits an illegal reversal by assuming that meeting a necessary requirement (ten years experience) is enough to guarantee the outcome (board position).

Step-by-Step Solution

1
Analyze the prompt's task to identify the specific logical flaw being tested.
The question asks to identify arguments confusing a necessary condition with a sufficient condition. This includes illegal reversals and illegal negations.
Understanding the exact flaw to look for prevents selecting arguments with different structural errors or perfectly valid reasoning.
2
Diagram and evaluate the argument about the symphony selection.
Premise: Selected -> Brass Section. Conclusion: ~Selected -> ~Brass Section. This is an illegal negation.
The argument incorrectly assumes that failing to meet the sufficient condition guarantees failing the necessary condition.
3
Diagram and evaluate the argument about the executive board candidate.
Premise: Board Position -> 10+ Years Experience. Conclusion: 10+ Years Experience -> Board Position. This is an illegal reversal.
The argument incorrectly assumes that fulfilling the necessary condition guarantees the sufficient condition.
4
Evaluate the remaining arguments to verify they do not commit this specific flaw.
The medication argument is valid (~Phase III -> ~Approved). The vegetable argument assumes causation from correlation. The transit policy argument shifts the meaning of a key term (equivocation).
Process of elimination confirms that only the symphony and executive board arguments commit the targeted conditional flaw.

Key Concept

Necessary vs. Sufficient Condition Flaws (Illegal Reversals and Negations)
Estimated Time:2m 0s
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Topics

Necessary vs. Sufficient Condition Flaws

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