I've recently been reading the 3rd edition Basic Fantasy RPG book, and on page fifteen it states that: "Some spells are reversible," and indicates that these spells are marked in the spell listings.
One such spell is Bless, which can be reversed to Bane another is Cure Light Wounds which can be reversed to be Cause Light Wounds.
Reading these spells it sounds like they are one spell that can be cast two ways, but that seems somewhat overpowered in this old school system. My question is: are spells that can be reversed one spell that can be cast two ways or are they two spells which must both be learned independently in order to cast them?
If possible, please provide a reference with your answer.