contrapositive

4 triples
GPTKB property

Random triples
Subject Object
gptkb:converse_Barcan_formula ◇∀xP(x) → ∀x◇P(x)
gptkb:raven_paradox All non-black things are non-ravens
gptkb:Soundness_theorem if a formula is not valid, then it is not provable
gptkb:Barcan_formula ◇∃xφ(x) → ∃x◇φ(x)