In the classical square of opposition, if 'Some S is P' is given as true, then which of the following can be immediately inferred from it?

1.'Some S is not P' is false

2.'Some S is not P' is true

3.'No S is P' is false

4.'All S is P' is undetermined

5.'Some S is not P' is undetermined

A1, 3 & 4 only

B3, 4 & 5 only ✓ Correct

C2, 3 & 4 only

D2 & 3 only

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

Explanation

With "Some S is P" true, the true readings are that E is false while A and O stay undetermined, giving 3, 4 and 5.

I and E are contradictories, so a true I makes "No S is P" false.

A stands above I as its superaltern, so a true I leaves "All S is P" undetermined.

I and O are subcontraries, so a true I leaves "Some S is not P" undetermined.

Hence the secured results are E false, A undetermined and O undetermined.

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