- #26

yossell

Gold Member

- 365

- 16

But: Phi -> (Psi -> (Phi & Psi)) is a tautology, so all instances of it are axioms. So, if you can prove Phi, and you can prove Psi then, by this axiom and two instances of Modus Ponens, you can prove the conjunction.

But now we've got to try and work out how to get that final universal quantifier in place...damn this system...