Can a "theurge" prestige class increase the level of a different "theurge" prestige class?

Question

Consider a build something along these lines:

• Wizard (some levels)
• Cleric (some levels)
• Mystic Theurge (advancing Wizard and Cleric spellcasting)
• Binder (some levels)
• Anima Mage (advancing Binder and Mystic Theurge spellcasting)

Can that last class choice of Anima Mage actually advance Mystic Theurge?

The Anima Mage's Spellcasting class feature says:

... [Y]ou gain spells per day and an increase in caster level... as if you had also gained a level in an arcane spellcasting class to which you belonged before adding the prestige class level.

Mystic Theurge has a class feature of "Spellcasting", and half of the Mystic Theurge's spellcasting is arcane, so it seems to qualify as an arcane spellcasting class. If this is true, then advancing the Mystic Theurge's spellcasting level in this way would advance both the wizard and the cleric's spellcasting, leading to every Anima Mage level advancing Binder, Wizard, and Cleric. By RAW, is this correct?

Answer 1

No, or at least pretty much everyone agrees you can’t

As Thomas Jacobs says, there is no hard-and-fast definition given by the books for “spellcasting class.” Various non-book sources (FAQ, Customer Service, and so on) have repeatedly denied the ability to advance mystic theurge with another prestige class that advances a “spellcasting class,”¹ but such sources are not officially a part of the rules (per errata documents).²

That said, a community consensus does exist,³ and it is just about universal:

A class that advances spellcasting is not, itself, a spellcasting class; a spellcasting class is one that has its own spells.

So, with that in mind:

• assassin, bard, blackguard, cleric, druid, paladin, ranger, sorcerer, and wizard are the core spellcasting classes, even though some of them are prestige classes.

• arcane archer, arcane trickster, archmage, dragon disciple, eldritch knight, hierophant, lore master, mystic theurge, and thaumaturgist are not, even though they require or advance spellcasting.

The classes in the first list could all be advanced by mystic theurge, and the arcane ones (assassin, bard, sorcerer, wizard) could be advanced by anima mage, but the classes in the second list cannot be advanced by anima mage, even the ones that advance arcane magic.

There are two prestige classes, legacy champion in Weapons of Legacy and uncanny trickster in Complete Scoundrel, who can advance any other class. These prestige classes could advance mystic theurge and therefore advance two other spellcasting classes, one arcane and the other divine.

1. ^{I cannot find the precise location of these mentions, but I do find reference to it (and to the fact that this stuff keeps getting deleted).}

   ^{As StevenO mentioned, we hashed this argument out ages and ages ago (circa 2004, I think - as soon as the Mystic Theurge was previewed pre-3.5, in fact, as it was the first dual-caster out there). However, most of the threads discussing this were destroyed in assorted board purges, and I don't see the discussion in the official FAQ either. We did get a Sage ruling on this and, unusually, a unanimous response from customer service (believe me, that is bizarre!), along with a solid consensus from die-hard rules lawyers who were more adept with mathematical logic than I (see, for instance, our threads discussing the world damage record, most of LordofProcrastination's dirty tricks, or any serious thread discussing either Pun-Pun or his challengers, which frequently delve into cardinality, infinity, and philosophy of time as well).}

2. ^{You can find all errata for 3.5 on Wizards’ official page for 3.5 updates; each errata file opens with a section explaining how errata works and defining primary and secondary sources. At best, the FAQ and CustServ are secondary to literally everything else, but most don’t grant them even that title. See here for more on what is wrong with the 3.5 FAQ.}

3. ^{Quick examples of community consensus:
   • Here’s one thread, with one voice of disagreement
   • A second thread with no disagreement, but an unanswered call for evidence
   • Another thread with no disagreement (and an alternate interpretation of why this doesn’t work)
   • Plus I managed to find one from Wizards.com, rather difficult these days (scroll down, it’s the last four posts of the thread).
   • The Mystic Theurge Optimization Handbook makes no mention of the possibility, but lists “No Special Abilities for advancing levels” as a disadvantage; this would not be an issue if you could just progress mystic theurge with some other prestige class. It also does not use such an option in any of its example builds, which it doubtlessly would if it were considered valid.
   Note in all cases that this is taken as obvious; the consensus is really strong and most don’t realize there is any ambiguity about it.}

Answer 2

Answer: Probably not, but ask your DM.

3.5e is notorious for not defining things regarding spellcasting. Nowhere is it defined exactly what a spellcasting class is. PHB 1 p. 174 mentions the following:

Names of spellcasting classes are abbreviated as follows: bard Brd; cleric Clr; druid Drd; paladin Pal; ranger Rgr; sorcerer Sor; wizard Wiz.

These are all the spellcasting classes in the book, making "being able to cast spells" a possible definition of a spellcasting class.

But are Theurge classes spellcasting classes?

There is no definition regarding what an arcane spellcasting class is. Some will tell you that you have to cast arcane spells to be one, others say that it is bound to the classes themselves (bard, sorcerer, wizard). Looking at the mentioned spellcasting classes you have to be able to cast spells to be a spellcasting class. Theurges do not get spells on their own: instead they grant spellcasting levels in other classes rather than getting their own. This would mean that Theurges are not spellcasting classes because they don't have their own spells, and thus do not qualify as arcane spellcasting classes.

But because of the incredible vagueness of the wording involved it could be possible that you can use one Theurge class to serve as the basis for another. Given the large number of classes involved, however, your caster levels will not be on the same level as a solo-class character of that same level, making your magic less potent. Entering a Theurge class the hard way (Wizard 3/Cleric 3) is seen as undesirable given how far your levels will fall behind. A Wizard 3/Cleric 3/Mystic Theurge 10 will give your 16th level character casting like a 13th level Wizard/Cleric, giving you access to your 7th level spell as opposed to a Wizard 16 or Cleric 16 who is about to hit 9th level casting. As such, while you can cast quite a diverse scala of lower level spells your firepower will be limited.

If you present this to your DM and ask for permission to use Mystic Theurge as levels for Anima mage, and point out that it would not result in a game breaker, there is a fair chance your DM will let you play this character.

Answer 3

When you gain a level in a prestige class that raises your caster level and your spell level from another spellcasting class, the other spellcasting class MUST have it's own spell list.

i.e. You may gain a level in Arcane Trickster to raise the spellcasting levels of Wizard or Assasin because both have their own spell list, but not to raise the spellcasting levels of Mystic Theurge, Archmage, or any class without it's own spell list.

The reason is simple: Classes without a spell list are actually raising another class' spellcasting. These classes always clearly specify that they raise another class' spellcasting.