Consider the following premises. For all z, if z were a lawyer, then z is reading a book. For all z, if z reads a book, then z is a lawyer. For all z, z is a lawyer or z will not read a book. Can we infer the following from them? For all z, z is a lawyer if and only if z will read a book.
 From the fact that for all z, if z reads a book, then z is a lawyer, and that for all z, if z were a lawyer, then z is reading a book we can infer that for all z, z will read a book if and only if z is a lawyer. From the fact that for all z, z will read a book if and only if z is a lawyer we can infer that for all z, if z were a lawyer, then z is reading a book. From the fact that for all z, z is a lawyer or z will not read a book we can infer that for all z, if z reads a book, then z is a lawyer. Finally, from the fact that for all z, if z were a lawyer, then z is reading a book, and that for all z, if z reads a book, then z is a lawyer we can infer that for all z, z is a lawyer if and only if z will read a book. Therefore, the answer is yes.