wikipedia says "An inference rule containing no premises is called an axiom schema or it if contains no metavariables simply an axiom."
but why can't we trivially make a premise ("A is true") part of an axiom schema ("B -> C") by doing something like "A & B -> C"?
- what's the difference? (my background is some ugrad math)
- what's a concrete difference in what they can do?
thank you