Consider the following premises. exists x_12: U(x_12) <-> P_4(x_12). forall x_12: P_5(x_12) -> P_12(x_12). forall x_12: P_12(x_12) <-> Q_12(x_12). forall x_12: P_4(x_12) <-> P_5(x_12). forall x_12: ~Q_12(x_12). Can we infer forall x_12: U(x_12) from them?
 From forall x_12: P_12(x_12) <-> Q_12(x_12), forall x_12: ~Q_12(x_12) we can infer forall x_12: ~P_12(x_12). From forall x_12: P_5(x_12) -> P_12(x_12), forall x_12: ~P_12(x_12) we can infer forall x_12: ~P_5(x_12). From forall x_12: P_4(x_12) <-> P_5(x_12), forall x_12: ~P_5(x_12) we can infer forall x_12: ~P_4(x_12). Finally, from exists x_12: U(x_12) <-> P_4(x_12), forall x_12: ~P_4(x_12) we can infer exists x_12: ~U(x_12), which contradicts forall x_12: U(x_12). Therefore, the answer is no.