Contradictories
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
A and O are contradictories; so are E and I. Contradictories always have opposite truth values.
Show
If "All S are P" is true, "Some S are not P" is false — necessarily, and vice versa.
Watch for
This is the one square-of-opposition relation that survives every interpretation. The rest come with fine print.