Consider the following premises. ~t. R_12(a_12) -> t. forall x_12: R_12(x_12) <-> S_12(x_12). Can we infer ~S_12(a_12) from them?
 From forall x_12: R_12(x_12) <-> S_12(x_12) we can infer R_12(a_12) <-> S_12(a_12). From R_12(a_12) <-> S_12(a_12) we can infer S_12(a_12) -> R_12(a_12). From S_12(a_12) -> R_12(a_12), R_12(a_12) -> t we can infer S_12(a_12) -> t. Finally, from S_12(a_12) -> t, ~t we can infer ~S_12(a_12). Therefore, the answer is yes.