In Arkham Horror, an investigator must pay the sanity cost of a spell before making a spell check to see whether it would succeed. If the spell's sanity cost is X, and the investigator has only X sanity, can that investigator willfully attempt to cast the spell in order to go insane?
For example, Gloria has only 1 sanity, and she needs to reach the other side of Arkham all the way from St. Mary's Hospital, but moving there on foot will take her 5 turns due to some ongoing Mythos environment. She has the spell Withering, which has a sanity cost of 1. Even though she does not have the lore to cast it successfully, can she use that spell to go insane and teleport herself all the way to Arkham Asylum?
To recap: Spells cannot be used unless they can be paid, but can you game the system when the situation demands it such that you obtain the benefits of paying everything you have?