Carrés exacts et carrés déductifs / 9. Syntax and semantics adjunction $Re\dashv Ex$ [0033] / [003A] Translator’s Note 9·a. The proof is completely elementary, but I judge it far from being immediate… I might decide to write it up someday! Section 8. The "proof theory" of $\Cat$ [0032] Section 10. $\cate{Sub}$-exact squares and relational calculus [0034]