Consider the following premises. s_3 or ~R_12(a). ~s_3. forall x_12: R_12(x_12) <-> S_12(x_12). Can we infer S_12(a) from them?
 From forall x_12: R_12(x_12) <-> S_12(x_12) we can infer R_12(a) <-> S_12(a). From s_3 or ~R_12(a) we can infer R_12(a) -> s_3. From R_12(a) -> s_3, ~s_3 we can infer ~R_12(a). Finally, from R_12(a) <-> S_12(a), ~R_12(a) we can infer ~S_12(a), which contradicts S_12(a). Therefore, the answer is no.