OK, I'm ready to take a first pass at this.
A system may be said to use logic if and only if it meets the
following two criteria:
1) It must represent somehow within the system truth values.
This entails that it has to represent propositions about the world
(internal or external) and whether the proposition is true or false
(or somewhere in between).
2) It must use the truth value(s) in some sort of logical operation
(and, or, not, if-then-else, or fuzzy counterparts), and use the
results of the operations somehow in determining its behavior.
I think an organism with instincts will meet these criteria while
something like an apple tree or solar system will not. Any objections?
-- David McFadzean david@lucifer.com Memetic Engineer http://www.lucifer.com/~david/ Church of Virus http://www.lucifer.com/virus/