On page one of the tutorial we supposed that negative forms like

"No S are P"

could be symbolized in two standard ways. We chose one way:

~(%x)( Sx & Px )

But there is another standard way we have used:

(^x)( Sx > ~Px )

In the tutorial we had a particular sentence in mind:

(**) "No mammals are reptiles "

Now this could be symbolized in either of two ways:

(* in PL)                       



To show these two ways equivalent we'd do two derivations from one as premise to the other as conclusion. That's what you'll find in problems one and two. (Hint: if you can do one, you can do the other in just the opposite order.)

Justification:       Sentence: