On One Decidable Generalized Quantifier Logic Corresponding to a Decidable Fragment of First-Order Logic Natasha Alechina Abstract: On one decidable generalized quantifier logic corresponding to a decidable fragment of first­order logic Natasha Alechina Van Lambalgen (1990) proposed a translation from a language containing a generalized quantifier Q into a first­order language enriched with a family of predicates R_i , for every arity i (or an infinitary predicate R) which takes $Qx\phi(x, y_1, ..., y_n)$ to $\forall x (R(x, y_1, ..., y_n) \implies \phi(x, y_1, ..., y_n) )$ ($y_1, ..., y_n$ are precisely the free variables of $Qx\phi$). The logic of Q (without ordinary quantifiers) corresponds therefore to the fragment of first­order logic which contains only specially restricted quantification. We prove that it is decidable using the method of semantic tableaux. Similar results were obtained by Andreka and Nemeti (1994) using the methods of algebraic logic.