In the classical square of opposition, if 'Some S is not P' is true, then which of the following could be immediately inferred from it?

1.'Some S is P' is false

2.'All S is P' is false

3.'No S is P' is undetermined

4.'Some S is P' is undetermined

5.'All S is P' is undetermined

A1, 3 and 5 only

B2, 3 and 4 only ✓ Correct

C3, 4 and 5 only

D1, 2 and 3 only

Correct answer: (B) 2, 3 and 4 only

Explanation

With "Some S is not P" true, A is false while E and I stay undetermined, giving 2, 3 and 4.

A and O are contradictories, so a true O makes "All S is P" false.

E stands above O as superaltern, so a true O leaves "No S is P" undetermined.

I and O are subcontraries, so a true O leaves "Some S is P" undetermined.

Thus the secured results are A false, E undetermined and I undetermined.

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