Abstract:
We exhibit infinitely many semisimple varieties of semilinear De Morgan
monoids (and likewise relevant algebras) that are not tabular, but which have only tabular
proper subvarieties. Thus, the extension of relevance logic by the axiom (p → q) ∨ (q → p)
has infinitely many pretabular axiomatic extensions, regardless of the presence or absence
of Ackermann constants.
