Is there a roll to determine if a character knows of a spell's existence?

Question

Spellcraft can be used to identify a spell as it is being cast. Is there a roll to know of the existence of a spell? It seems like if you can identify a spell as it is being cast, you probably already know of the spell's existence. Or, maybe not? Maybe you can identify what magics that the components being used to cast a spell would produce, so you don't necessarily need to know of a spell's existence to identify it being cast?

I also looked up Knowledge skills, but they do not discuss knowing of a spell's existence. I would assume Arcana, Religion, and Nature could potentially be used to know of the existence of arcane, clerical/divine, and druidic/divine spells respectively. But, again, the DCs are not listed.

Obviously, the DM could adjudicate if this is not spelled out anywhere. And obviously, any spell whose existence a character did not know of, they could research. But, it is more the initial does my character know of a spell or not where I am wondering if there is a rule that describes this.

Answer 1

The game assumes all official spells are generally known; however, the GM could change this to suit their campaign.

There is not a rule that covers this. Since spell casting characters are free to select any spell from the spell lists to learn when they gain the appropriate level, the rules seem to imply that the official spells are all generally known and available to the spell casting public in the game world. Since the Spellcraft skill requires skill ranks (i.e., study and practice), we can assume that part of what goes into raising that skill's level is learning about the spells that are out there and available, even ones beyond the character's own level or outside the spells available to their class. For a real world comparison, consider a novice martial artist. They may very well know the moves a black belt is using, even if they cannot employ those moves themselves.

As a GM, you could decide that some official spells--and spells of your own creation--may be unknown to certain societies for whatever reason. For instance, the wizards of a desert nation separated by high mountains from every large body of water may not be aware of the Tsunami spell, and thus are unable to identify it when they see it being cast. You might also fence off a body of arcane spells as having belonged to an ancient civilization and they need to be rediscovered in ruins before they can be learned, cast, and identified. Certainly, it would be within the reasonable bounds of a GM's power to rule that a certain spell is not generally known and therefore cannot be identified by using Spellcraft unless the character attempting to identify it has seen the spell in use before, or found a way to learn about it before trying to identify it. Of course, as with all house rules for a given campaign, this should be communicated to players before they create characters so that they can make informed decisions. You should also consider game balance when so restricting spells.