I'm embarrassed as a GM I don't know this answer, but I need help so I'll just ask. The following situation is actually the first time this has come up in either of my campaigns. It's come up since we've been getting a feel for the new APG and the group thought it would be fun if I assigned a class from the APG to each of the six PCs. I have a Wizard 4/Witch 1, and a Sorcerer 4/Summoner 1. I'm confused on if the W/W can cast burning hands at CL 5, or if it's just CL 4 from the wiz and CL 1 if from the witch.
My question: If a character has multiple classes, specifically in spell-casting classes, how do you figure there Caster Level (CL)? Does it matter if the classes cast from the same spell list for example a Sorcerer 4/ Wizard 4. Since they have the same spell options to choose from would the CL be 8, or just 4?
My gut is telling me you treat the classes completely seperate and you have spells known, #/day, and CL independant. Any help is appreciated
AFAIK, the progression of spellcasting classes is completely separate.
It's only when a (generally prestige) class says "+1 to spellcasting class level" that you can add spellcasting levels towards another class.
In that regard, selecting different spellcasting classes without the goal of selecting a prestige class where both are used (mystic theurge, for instance) is generally accepted as a waste of resources.
Laughing Goblin and Louis speak the truth. Spellcasting only stacks when you have prestige classes giving the almighty "+1 caster level" ability. It is for this reason that the feat Practiced Spellcaster was so common in 3.5 and why Magical Knack is so often suggested to multiclass spellcasters in Pathfinder.
Think of it like this. A sorcerer learns to use the magic in their blood. The wizard is learning to control magic through study. These are two completely different methods of using magic, two different skillsets as it were. Making them stack doesn't make sense in that regard. It'd be like me saying that because I know how to sing, I also know how to play acoustic guitar so my musical ability is the sum of the two.
For this reason, multiclassing as a spellcaster into another spellcasting class is generally a poor choice, as nothing stacks between the classes. Even meeting the prerequisites for feats gets mucked with. The sole possible exception was in 3.5, where a specialist wizard might take a level or two of sorcerer to bypass restrictions from his schools regarding magic item use. But that's no longer the problem it once was.
