Which of the following statements are sub-contraries? (A) All nurses are…

CONCEPT

In the traditional square of opposition, A is a universal affirmative, E a universal negative, I a particular affirmative, and O a particular negative. Subcontraries are the I and O propositions: they may both be true, but they cannot both be false when the subject class has members.

APPLICATION

1. The proposition ‘Some nurses are caring human beings’ has the I form: Some S are P.

2. The proposition ‘Some nurses are not caring human beings’ has the O form: Some S are not P.

3. These particular affirmative and particular negative propositions occupy the subcontrary relation in the traditional square of opposition.

CROSS-CHECK AND CONTRAST

For a concrete check, a hospital may contain some caring nurses and some nurses who are not caring, so both particular propositions can be true. If the affirmative particular were false, no nurse would be caring; if the negative particular were also false, every nurse would be caring. Those two universal consequences cannot both hold for a non-empty class.

• ‘All nurses are caring human beings’ and ‘No nurses are caring human beings’ are the universal affirmative and universal negative forms; these are contraries.

• ‘All nurses are caring human beings’ and ‘Some nurses are not caring human beings’ are the universal affirmative and particular negative forms; these are contradictories.

• ‘No nurses are caring human beings’ and ‘Some nurses are caring human beings’ are the universal negative and particular affirmative forms; these are contradictories.

• ‘Some nurses are caring human beings’ and ‘Some nurses are not caring human beings’ are the two particular forms; these are subcontraries.

Hence, the required pair is “Some nurses are caring human beings” with “Some nurses are not caring human beings.”