Which pair of propositions stands in a relation where the truth of one implies the truth of the other, but not conversely (subalternation)?

AAll plastics are synthetic (implies 'Some plastics are synthetic') ✓ Correct

BSome plastics are synthetic

CSome plastics are not synthetic

DNo plastics are synthetic

Correct answer: (A) All plastics are synthetic (implies 'Some plastics are synthetic')

Explanation

All plastics are synthetic implying Some plastics are synthetic illustrates subalternation.

Subalternation runs from a universal to its corresponding particular of the same quality.

The truth of the universal guarantees the truth of the particular falling under it.

The reverse does not hold, since the particular being true leaves the universal undecided.

This one-way descent from all to some is exactly the subalternation relation.

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