At 13:40 26/11/04 -0500, Hal Ruhl wrote:
What does "logically possible" mean?
A proposition P is logically possible, relatively to
1) a consistent set of beliefs A
2) the choice of a deduction system D (and then consistent
means "does not derive 0=1).
if the negation of P is not deductible (in D) from A.
Concerning many theories, to say that a proposition
(or a set of propositions) A is logically possible
is the same as saying that A is consistent (i.e you
cannot derive 0 = 1 from it), or saying that A has a
model (a reality, a mathematical structure) satisfying
it.
Bruno
http://iridia.ulb.ac.be/~marchal/
