Consider the following premises. For all x_4, x_4 is a politician if and only if x_4 is a sailor. For all x_4, if x_4 were a lawyer, then x_4 is a sailor. For all x_4, x_4 is not a politician. For all x_4, if x_4 were a sailor, then x_4 is a lawyer. Can we infer the following from them? There is at least one x_4 for which x_4 is a lawyer.
 From the fact that for all x_4, x_4 is a politician if and only if x_4 is a sailor, and that for all x_4, x_4 is not a politician we can infer that for all x_4, x_4 is not a sailor. From the fact that for all x_4, if x_4 were a lawyer, then x_4 is a sailor, and that for all x_4, if x_4 were a sailor, then x_4 is a lawyer we can infer that for all x_4, x_4 is a lawyer if and only if x_4 is a sailor. Finally, from the fact that for all x_4, x_4 is a lawyer if and only if x_4 is a sailor, and that for all x_4, x_4 is not a sailor we can infer that for all x_4, x_4 is not a lawyer, which contradicts that There is at least one x_4 for which x_4 is a lawyer. Therefore, the answer is no.