Consider the following premises. forall x_18: W(x_18) -> S_1(x_18). forall x_18: S_1(x_18). forall x_18: S_1(x_18) -> W(x_18). Can we infer W(a_9) or s_2 from them?
 From forall x_18: W(x_18) -> S_1(x_18), forall x_18: S_1(x_18) -> W(x_18) we can infer forall x_18: W(x_18) <-> S_1(x_18). From forall x_18: W(x_18) <-> S_1(x_18) we can infer forall x_18: S_1(x_18) -> W(x_18). From forall x_18: S_1(x_18) -> W(x_18), forall x_18: S_1(x_18) we can infer forall x_18: W(x_18). From forall x_18: W(x_18) we can infer W(a_9). Finally, from W(a_9) we can infer W(a_9) or s_2. Therefore, the answer is yes.