One of the basic theorems in universal algebra is Birkhoff's variety theorem: the smallest equationally axiomatizable class containing a class K of algebras coincides with the class obtained by taking ...

Mathematics is distinguished from the sciences by the freedom it enjoys in choosing basic assumptions from which consequences can be deduced by applying the laws of logic. We call the basic ...

This is a preview. Log in through your library . Journal Information The Journal of Philosophical Logic provides a forum for work at the crossroads of philosophy and logic, old and new, with ...