Consider the following premises. forall x_13: S(x_13) <-> T(x_13). exists x_13: T(x_13) -> S(x_13). forall x_13: ~P_8(x_13). forall x_13: P_8(x_13) or ~T(x_13). Can we infer forall x_13: S(x_13) from them?
 From forall x_13: S(x_13) <-> T(x_13) we can infer forall x_13: S(x_13) -> T(x_13). From forall x_13: P_8(x_13) or ~T(x_13) we can infer forall x_13: T(x_13) -> P_8(x_13). From exists x_13: T(x_13) -> S(x_13), forall x_13: S(x_13) -> T(x_13) we can infer exists x_13: T(x_13) <-> S(x_13). From forall x_13: T(x_13) -> P_8(x_13), forall x_13: ~P_8(x_13) we can infer forall x_13: ~T(x_13). Finally, from exists x_13: T(x_13) <-> S(x_13), forall x_13: ~T(x_13) we can infer exists x_13: ~S(x_13), which contradicts forall x_13: S(x_13). Therefore, the answer is no.