For which of the following forms of categorical propositions conversion is…
2022
For which of the following forms of categorical propositions conversion is valid?
(A) Some S is P
(B) Some S is not P
(C) No S is P
(D) All S is P
Choose the correct answer from the options given below:
Answer: B. A, C and D Only — ConceptConversion is an immediate inference formed by interchanging the subject and predicate while preserving the proposition’s quality. A conversion is…
- A.
A, B, C, D Only
- B.
A, C and D Only
- C.
B, C and D Only
- D.
A, B and D Only
Attempted by 6 students.
Show answer & explanation
Correct answer: B
Concept
Conversion is an immediate inference formed by interchanging the subject and predicate while preserving the proposition’s quality.
A conversion is valid only when the converse does not distribute a term that was undistributed in the original. In traditional categorical logic, E and I convert simply, A converts by limitation when its subject class has existential import, and O does not convert.
Application
Proposition | Type | Conversion |
|---|---|---|
A: Some S is P | I | Some P is S (simple conversion) |
B: Some S is not P | O | No valid conversion |
C: No S is P | E | No P is S (simple conversion) |
D: All S is P | A | Some P is S (conversion by limitation) |
Contrast
The set A, B, C and D includes B, the O-proposition, whose conversion is not valid.
The set A, C and D contains the I- and E-propositions that convert simply and the A-proposition that converts by limitation.
The set B, C and D includes B, the O-proposition, and omits A, whose conversion is valid.
The set A, B and D includes B, the O-proposition, and omits C, whose conversion is valid.
Result
Therefore, under the traditional interpretation with existential import, conversion is valid for A, C and D only.