a. Soldiers do not go to that bar but sailors do. b. Doctors do not use these equations but engineers do. c. Cats do not attack big rats but dogs do. I think in (a) it is obvious that only some sailors go to that bar and not all sailors. It seems to me that (b) does not necessarily imply that all engineers use these equations. Does (c) imply that all dogs attack big rats? Many Thanks. Azz.