"Otherwise" Statements

[DavidS674]

After doing game PT 55 s2 game 4 I'm wondering does an "otherwise" statement always imply a biconditional? If not, how do I distinguish between when it does and doesn't? I think I've been pretty solid on conditional reasoning so far but this term is confusing to me.

[Misti Duvall]

Yeah, that is one tricky rule! When used as it's used in PT55, G4, otherwise does indicate a biconditional. The key is that it's giving a second piece of information, which is what biconditionals always do (give two pieces of information). Off the top of my head, I can't think of an LG rule that would use otherwise in another way.

The bottom line: if you've got two conditional rules that are reversals or negations of each other, it's a biconditional. Sometimes these are written as two separate rules and sometimes they're written in the same rule.