Which of the following propositions are so related that they cannot both be false, though they can both be true?

Statements 1 and 3 are the pair that cannot both be false yet can both be true.

Statement 1, 'Some poems are artworks', is a particular affirmative.

Statement 3, 'Some poems are not artworks', is the matching particular negative on the same terms.

A particular affirmative and its particular negative are subcontraries, which may both be true but never both false.

Statement 2 is universal and Statement 4 is merely the converse of Statement 1, so neither forms this relation.

Thus the subcontrary pair is the first and the third.