To see how Logic really works, it is simplest to proceed by example.
We'll present three example sets plus discussion. The first is drawn
from computing, where ``logic'' is the bread and butter of existence and
where the *engineering* requirements do their best to exclude or
manage ``impossible'' cases. The second is drawn from propositional
logic, which is the kind of logic that is ``closest'' to the logic of a
computer program. Finally, we present an example drawn from predicate
logic, the logic of human language and rhetoric, which is in many ways
the most difficult to logically analyze. It is also a kind of logic
that openly encourages logic puzzles, paradoxes, and Gödellian knots.

Robert G. Brown 2007-12-17