Consider the following premises. If William were an artist, then James is a janitor. James is not a janitor. James is a janitor if and only if William is an artist. Can we infer the following from them? If we can, name the inference rule being used: William is an artist.
 From the fact that James is a janitor if and only if William is an artist we can infer that if James were a janitor, then William is an artist via biconditional elimination. From the fact that if James were a janitor, then William is an artist, and that if William were an artist, then James is a janitor we can infer that James is a janitor if and only if William is an artist via biconditional introduction. Finally, from the fact that James is a janitor if and only if William is an artist, and that James is not a janitor we can infer that William is not an artist via biconditional elimination, which contradicts that William is an artist. Therefore, the answer is no.