Which of the following statements are logically equivalent to the statement Some professors are spiritualists?

1.Some spiritualists are professors.

2.Some non-spiritualists are not non-professors.

3.No spiritualists are professors.

4.Some professors are not non-spiritualists.

A1, 2 & 4 only

B1 & 4 only ✓ Correct

C2 & 3 only

D3 & 4 only

Correct answer: (B) 1 & 4 only

Explanation

Statements 1 and 4 are logically equivalent to some professors are spiritualists.

Statement 1, some spiritualists are professors, is the valid converse of the I form.

Statement 4, some professors are not non-spiritualists, is the obverse of the same I form.

Both conversion and obversion of an I proposition preserve its exact meaning.

Only the converse and the obverse retain the full logical force of the original I proposition.

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