Consider the following premises. w -> ~P_18(a_18). forall x_18: P_18(x_18). r. Can we infer w from them? If possible, name the inference rules being used at each step.
 From forall x_18: P_18(x_18) we can infer P_18(a_18) via universal instantiation. Finally, from w -> ~P_18(a_18), P_18(a_18) we can infer ~w via modus tollens, which contradicts w. Therefore, the answer is no.