Consider the following premises. For all x, x is an artist if and only if x will take a plane. For all x, if x takes a plane, then x is an artist. For all x, if x were an artist, then x is taking a plane. Can we infer the following from them? There is at least one x for which if is not true that x will take a plane if and only if x is an artist.
 From the fact that for all x, if x were an artist, then x is taking a plane, and that for all x, if x takes a plane, then x is an artist we can infer that for all x, x is an artist if and only if x will take a plane. From the fact that for all x, x is an artist if and only if x will take a plane we can infer that for all x, if x were an artist, then x is taking a plane. From the fact that for all x, x is an artist if and only if x will take a plane we can infer that for all x, if x takes a plane, then x is an artist. Finally, from the fact that for all x, if x takes a plane, then x is an artist, and that for all x, if x were an artist, then x is taking a plane we can infer that for all x, x will take a plane if and only if x is an artist, which contradicts that There is at least one x for which if is not true that x will take a plane if and only if x is an artist. Therefore, the answer is no.