In the classical square of opposition, if 'All S is P' is given as false, then which of the following could be immediately inferred from it?

1.'No S is P' is true

2.'Some S is not P' is false

3.'Some S is not P' is true

4.'No S is P' is undetermined

5.'Some S is P' is undetermined

A1, 3 and 5 only

B3, 4 and 5 only ✓ Correct

C2, 4 and 5 only

D1, 2 and 5 only

Correct answer: (B) 3, 4 and 5 only

Explanation

With "All S is P" false, O is true while E and I stay undetermined, giving 3, 4 and 5.

A and O are contradictories, so a false A makes "Some S is not P" true.

A and E are contraries, so a false A leaves "No S is P" undetermined.

A false A also leaves its subaltern I, "Some S is P", undetermined.

Thus O true, E undetermined and I undetermined are the secured results.

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