Submitted by antarchi on February 19, 2008 - 14:51.
Among the valuable properties that logical systems can have are:
* Consistency, which means that none of the theorems of the system contradict one another.
* Soundness, which means that the system's rules of proof will never allow a false inference from a true premise. If a system is sound and its axioms are true then its theorems are also guaranteed to be true.
* Completeness, which means that there are no true sentences in the system that cannot, at least in principle, be proved in the system.
From wikipedia