Under the conventional existential-import rule used in aptitude-test…

2021

Under the conventional existential-import rule used in aptitude-test syllogisms, if “All successful administrators are intelligent” is true, which of the following statements follows?

Answer: B. Some successful administrators are intelligentCONCEPTA universal affirmative proposition has the form “All S are P”, represented as S ⊆ P. In the conventional syllogism rules used in aptitude tests, the…

  1. A.

    No successful administrator is intelligent

  2. B.

    Some successful administrators are intelligent

  3. C.

    Some successful administrators are not intelligent

  4. D.

    Some intelligent people are not successful administrators

Show answer & explanation

Correct answer: B

CONCEPT

A universal affirmative proposition has the form “All S are P”, represented as S ⊆ P. In the conventional syllogism rules used in aptitude tests, the subject class S is treated as non-empty, so the universal affirmative has existential import.

Under subalternation, an A-form proposition therefore supports the corresponding I-form proposition “Some S are P”. It does not support the contrary E-form, the contradictory O-form, or an existence claim about the part of P outside S.

APPLICATION

  1. Let S be the set of successful administrators and I be the set of intelligent people.

  2. The premise “All successful administrators are intelligent” gives S ⊆ I.

  3. By the conventional existential-import assumption, S is non-empty; choose an element x in S.

  4. Since S ⊆ I, the same element x is also in I. Hence at least one successful administrator is intelligent.

CONTRAST

  • “No successful administrator is intelligent” makes S and I disjoint, contrary to S ⊆ I with non-empty S.

  • “Some successful administrators are not intelligent” requires an element of S outside I, contradicting S ⊆ I.

  • “Some intelligent people are not successful administrators” needs an element in I outside S; the premise does not guarantee that region is occupied.

CROSS-CHECK

Draw the S circle entirely inside the I circle and place one witness in S. That witness necessarily lies in both circles, while no witness is forced into the I-only region.

Therefore, the statement that follows is “Some successful administrators are intelligent”.

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