User:Lord Farin/Backup/Definition:Natural Deduction/Elementary Valid Argument Forms

Definition
In most treatments of PropLog various subsets of the following rules are treated as the axioms. Some of them are obvious. Others are more subtle.

These rules are not all independent, in that it is possible to prove some of them using sequents constructed from combinations of others. However, when a set of proof rules is selected as the axioms for any particular treatment of this subject, those rules are usually selected carefully so that they are independent.

Also known as
Some sources refer to axioms of natural deduction as '''elementary valid argument forms. It can be argued that, as no set of proof rules is intrinsically "axiomatic", this term is preferable.