Is there a difference between "Able to cast x lvl spells" and "Ability to cast x lvl spells"?

Question

I was looking at the Eldritch Knight prestige class and saw one of its requirements is "Able to cast 3rd-level arcane spells." I thought "Hmm, well my 1st level sorc with 18 Charisma is "able to cast 3rd lvl arcane spells" because his stat is high enough, so if I took Fighter at second level then I should be able to start Eldritch Knight at 3rd." My DM disagrees, reading it as "you have to be a 5th lvl wizard, or 6th lvl sorcerer, etc., to be able to cast 3rd lvl spells."

Most of the prestige classes I see have the same wording, so I figured that was a valid view of it. But then I saw that the Savant prestige class has a slightly different wording for its requirement: "Ability to cast 2nd-level spells."

This made me think they decided to differentiate: to me, while a 1st level wizard might be "able" to cast 2nd level spells because he has 12 int, he doesn't have the "ability" to cast them.

I noticed that most of the time, prestige classes that want to hold level entry at a minimum level will put in direct skill requirements: Dragon Disciple requires 5 Knowledge (Arcana) skill ranks. This means you can't enter it until your 6th level, because you can't have 5 points in a skill until level 5. This is cut and dried with no potential for confusion.

I think that your stat (assuming you have a casting class) being high enough should qualify you as being "able" to cast whatever level spell is specified, though you might not have the "ability" yet. It opens up some more interesting options to casters who might want to get going down a particular road if they don't mind trading in special class abilities for whatever prestige class they're qualifying for.

Answer 1

Your GM is correct. Until you are higher level you are not able to cast higher level spells. The entire point of prestige class entry requirements is to gate entry to more experienced characters, and your interpretation basically reduces to just saying "an arcane spellcaster" which if that's what they meant, it's what they'd say. You need to actually be able to cast the spell, so you need appropriate level + high enough stat + correct class + not having swapped out your spellcasting ability for some other ability and so on.

Remember that this is supposed to represent some kind of in game qualification.

"Welcome to the Guild of Master Evokers! So you want to join, eh?"

"Yes!"

"OK, show us your stuff, cast something big - you know, a fireball or whatever."

"Well, I can't now - but I have the ability to one day!"

"What does this look like, Hogwart's? Don't let the door hit you in the ass on the way out."

In this context, "able to cast" and "ability to cast" mean the same thing. The designers' neglecting to use the exact same verbiage for every writeup is... pretty typical, actually, and not indicative of any deliberate nuance.

Also there seems to be a misunderstanding about a high stat possibly letting you cast higher level spells early - this is not the case. "In addition to having a high ability score, a spellcaster must be of a high enough class level to be able to cast spells of a given spell level." -d20PFSRD

Answer 2

I'm not a native English speaker, so downvote me if I'm wrong, but I understand able as something that can be done. A newborn bird has wings, but he is not able to fly until he fully develops them, and learns how to. More complex example: a plane is not able to fly if the fuel tank is empty, until it is refuelled.

But as I said, I'm not a native speaker, so I must do my research. I think in the wiktionary definition this aception applies:

4.Having the necessary powers or the needed resources to accomplish a task.

Has a level 1 wizard the necessary powers or the needed resources to cast 2nd level spells? Well, again I'm not the most suited to answer, but I think he hasn't. So he isn't able to cast 2nd level spells until he levels up.

Answer 3

“Able to cast” and “Ability to cast” are identical under the rules

There is no difference between the wording of these prerequisites. Both refer to the ability to cast a spell of the required level (as in, you can actually cast the spell and have its effect take place), as a spell (Spell-like Abilities don’t usually count), and of the appropriate sort (Arcane or Divine) if relevant (Sorcerers are Arcane).

High ability modifiers do not give you higher-level spell slots

Furthermore, you do not get bonus spells of a given level unless you can already cast spells of that level.

In addition to having a high ability score, a spellcaster must be of a high enough class level to be able to cast spells of a given spell level.

See the Abilities and Spellcasters if you don’t believe me. You have to scroll down below the table to read the rules for how the table works.

So a Sorcerer 1 with 18 Charisma gets 1 bonus 1st-level spell, and zero bonus 2nd-level, 3rd-level, and 4th-level spells, despite what the table says, because a Sorcerer 1 cannot cast 2nd-level, 3rd-level, or 4th-level spells. If you had 20 Charisma, you’d get 2 bonus 1st-level spells, but still no spells of higher level, until you get more Sorcerer levels.

This is why spellcasters usually don’t multiclass

Generally speaking, spellcasters multiclass poorly because of this: the only way to get higher-level spells is to keep taking spellcasting levels. Martial characters may get slower BAB when they take other classes, but they still get BAB. Skill-based characters may get fewer skill points from levels in other classes, but they still get skill points (and their max rank still increases). And in both of those cases, they can still take feats or prestige classes that require BAB or skill ranks because they’re still getting those things. Spellcasters, however, can only get more spells by continuing in their own class (or a prestige class that advances it).

This is why the “holy mantra” of 3.x optimization, listed twice on the unofficial “Ten Commandments,” is “Thou shalt not lose spellcasting levels.” Spells are the most powerful thing, and you only get them by continuing to take spellcasting levels. I don’t want to oversell things here – optimization is a minor part of the game at most tables, and is actively frowned upon in many – but to the degree to which you do care about mechanical power, lost spellcasting levels should be considered very carefully.