Consider the following premises. Charles is making tea. For all y, y is a lawyer if and only if y will make tea. Can we infer the following from them? If we can, name the inference rule being used: For all y, y is not a lawyer.
 From the fact that Charles is making tea we can infer that there is at least one y for which y will make tea via existential generalization. From the fact that for all y, y is a lawyer if and only if y will make tea we can infer that for all y, if y makes tea, then y is a lawyer via universal biconditional elimination. Finally, from the fact that for all y, if y makes tea, then y is a lawyer, and that there is at least one y for which y will make tea we can infer that there is at least one y for which y is a lawyer via existential modus ponens, which contradicts that For all y, y is not a lawyer. Therefore, the answer is no.