ABSTRACT
Let T be the term algebra as before. Let R c be the relation of interdeduci b ility w ith respect to LK , and let Ac be the class of all models of R c ; the algebras in Ac I shall call c-algebras. There holds the
THEOREM l c Ac is the class of all algebras A = < u (A ), 3 , n , u > w ith a distinguished element e in A which, in addition to ( a ^ ) ,
and Ac is also the the class of all algebras defined by the set D c consisting of D i together with this equation.
