Originally Posted by

**bryangoodrich** I checked my textbook this morning that has a list of the rules, and I see how it works. Though, the book lists that it requires the extra step I mentioned--i.e., to close the assumptions with conditionals. Then we get the argument form

$\displaystyle A \lor B$

$\displaystyle A \rightarrow C$

$\displaystyle B \rightarrow C$

$\displaystyle \vdash C$

This formulation doesn't use ranges of justification, which threw me off. The ideas and necessary steps are pretty much the same, clearly, but I think this specification is more intuitive since it requires specifying what we conclude from the assumption blocks.