The relation between two particular propositions that have the same subject and predicate but differ in quality is

Two particulars with the same subject and predicate differing in quality stand in sub-contrary opposition.

These are the I and O propositions.

They share quantity, both being particular, but oppose in quality.

Sub-contraries cannot both be false, though both may be true.

This same-quantity, opposite-quality pair of particulars is the sub-contrary relation.