This is a standard type of puzzle; you can buy whole books
of this kind of thing (Raymond Smullyan has several). Indeed,
the assumptions are that the speakers know each other, and
that the statements can be taken at face value as being
either true (coming from truthtellers) or false (coming
from liars). I'll bet Jack is very familiar with these
puzzles, and didn't think to spell out the ground rules
explicitly (I haven't looked at the draft text myself);
it may not be reasonable to assume that his intended audience
is familiar with these puzzles, though, and so a more thorough
explanation of what they're about might be in order.
In any case, these are logic puzzles, intended to get one thinking
about logical consistency and contradictions, and not intended
to model any real-world behavior of actual people.
Hope this helps -
Sue Willis
Suzanne Willis, Professor, Physics Department
Northern Illinois University, DeKalb, IL 60115 USA http://niuhep.physics.niu.edu/~willis/ swillis@niu.edu
phone: 815-753-0667 fax: 815-753-8565