Which of the following statements are so related that they cannot both be…
2023
Which of the following statements are so related that they cannot both be false, although they can both be true?
A. Some professors are spiritualists.
B. All professors are spiritualists.
C. No professors are spiritualists.
D. Some professors are not spiritualists.
Choose the correct answer from the options given below:
Answer: C. A & D only — CONCEPTIn the traditional square of opposition, categorical propositions are classified by quantity (universal or particular) and quality (affirmative or…
- A.
B & C only
- B.
B & D only
- C.
A & D only
- D.
A & C only
Show answer & explanation
Correct answer: C
CONCEPT
In the traditional square of opposition, categorical propositions are classified by quantity (universal or particular) and quality (affirmative or negative).
The particular affirmative I-form and the particular negative O-form are subcontraries: they cannot both be false, although they can both be true.
APPLICATION
A (‘Some professors are spiritualists’) is a particular affirmative, or I-form, proposition.
B (‘All professors are spiritualists’) is a universal affirmative, or A-form, proposition.
C (‘No professors are spiritualists’) is a universal negative, or E-form, proposition.
D (‘Some professors are not spiritualists’) is a particular negative, or O-form, proposition.
Thus A and D instantiate the I–O pair described in the stem.
CONTRAST
B and C form the A–E contrary pair: they cannot both be true, but they can both be false.
B and D form an A–O contradictory pair: they cannot both be true and cannot both be false.
A and C form an I–E contradictory pair: they cannot both be true and cannot both be false.
RESULT
The required pair is A and D only.