Definition:Interderivable

If two statements $$p$$ and $$q$$ are such that:


 * $$p \vdash q$$, i.e. $$p$$ therefore $$q$$
 * $$q \vdash p$$, i.e. $$q$$ therefore $$p$$

then $$p$$ and $$q$$ are said to be interderivable.