Corrigendum to 'Categorical abstract algebraic logic: The criterion for deductive equivalence'

摘要

We give a correction to the paper [2] mentioned in the title. I was recently made aware that a good colleague of mine from the Universitat de barcelona, Jose Gil-Ferez, has provided in [1] a counterexample to my Theorem 13 (the Criterion for Deductive Equivalence) of [2]. Moreover, despite the fact that I have not yet seen Jose's counterexample, I have now discovered a simple, but grave, mistake in the proof of the key Lemma 9 of [2].