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

1.'Some S is not P' is false

2.'Some S is P' is true

3.'Some S is not P' is undetermined

4.'Some S is P' is undetermined

5.'No S is P' is false

A1, 2 and 5 only ✓ Correct

B1, 4 and 5 only

C2, 3 and 5 only

D3, 4 and 5 only

Correct answer: (A) 1, 2 and 5 only

Explanation

From the true A, 'Some S is not P' is false, 'Some S is P' is true, and 'No S is P' is false.

The proposition given true is A type, 'All S is P'.

Its contradictory O, 'Some S is not P', therefore must be false.

Its contrary E, 'No S is P', cannot be true alongside a true A, so E is false.

By subalternation a true A makes its particular 'Some S is P' true.

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