[RPG] Why are high ability scores mandatory to cast spells

ability-scoresdnd-3.5emagic

After reading this answer, I was once again struck by the fact that a Dungeons and Dragons 3.5 spellcaster, no matter his level, is unable to overcome the limits imposed by his ability scores.

Like most classes that cast spells, the paladin, for example, has this sentence in its description of the class feature spells:

To prepare or cast a spell, a paladin must have a Wisdom score equal to at least 10 + the spell level.

Thus a paladin, no matter his level, is unable to cast spells if his Wisdom score is 10 or less. He can be a level 20 paladin, commander the holy and orderly hordes, lauded by all good and organized folk, feared by evil and chaotic creatures throughout the planes, his god's bloody right hand of vengeance and wrath, yet, because his Wisdom is only 10, he can't cast spells.

  1. How can a DM explain this limit to a player when the player wants his character to be able to cast spells, but the player is, for example, either unconcerned with his character's bonus spells and saving throw DCs or more concerned with an accurate statistical picture of his character than the mechanical benefits a different picture would yield?

    For example, how does the DM explain in a narrative fashion that a character must have a high Intelligence score to realize fully the wizard's spellcasting so his concept of an addled, not-so-bright but patient and persistent wizard is invalid? Likewise, that a character must have a high Wisdom score to realize fully the cleric's spellcasting so his concept of an oblivious, judgment-impaired but dedicated and devout cleric is also invalid?

  2. Mechanically, why does this restriction exist? That is, are there technical reasons to tie a character's maximum spell level to his ability score directly rather than, for example, to his class's standard spellcasting progression? I'm not looking for developer commentary (although that's great if it's available) but for game elements that make this connection necessary.

    Does, for example, a wizard need an Intelligence score of at least 10 or does a paladin need a Wisdom score of at least 11 for anything else besides satisfying that one line in the description of the class's spells class feature? Does the game for some reason descend into anarchy if, for example, a Wiz17 with an Intelligence score of 6 can cast 9th-level wizard spells or a Pal15 with a Wisdom score of 3 can cast 4th-level paladin spells?

Best Answer

The History

This actually goes all the way back to the first OD&D supplement, Greyhawk. The maximum spell level a Magic-User could cast was now limited by his Intelligence. Although interestingly, Clerics were explicitly not limited by Wisdom. The justification was that, unlike Magic-Users, a Cleric's spells were divine gifts, not based upon their skill. Intelligence also limited how many spells the Magic-User had.

Speculating, this was probably partly simulationist and partly for mechanical reasons. Arcane magical ability is tied intelligence, both lore-wise and in the the Magic-User's prime requisite was Intelligence. High level spells are more complex (the spell level system is a direct mapping from Chainmail's complexity system) so there's logic to a smart Magic-User being able to handle more complex spells than an average one.

Your Ability Scores had little mechanical impact in OD&D, primarily a bonus to experience gain. Greyhawk began increasing the existing, minor bonuses and penalties and adding new ones. Intelligence affecting Magic-Users spells was part of this increasing affects from Ability Scores. And only Magic-Users with an Intelligence below 11 were actually losing anything compared to the core game, because the 7-9 level spells were added with Greyhawk, and did not exist before ability limits.

This Ability Score limit spread to Clerics with AD&D. High level spells required a certain Wisdom and a low Wisdom could cause spell failure. You may have noticed that Ability Scores were only limiting the casting of high level spells. As KRyan touched on, this is because of Prime Requisites / Ability Score requirements. RAW, you couldn't even play a caster with a below average Ability Score in their Prime Requisite.

The Implications

So there's the historical precedent, which explains where it comes from. Was there any other reason to carry it forward, beyond tradition? It makes your Ability Score have a greater effect on your casting. The fact that spell strength is often not based on your Ability Score seems like it could be unbalancing to ignore the Ability Score requirement. I doubt it would be that bad, but I'd ask a optimization expert about it.

I personally don't have a problem with the idea that magic is too complicated for the average (Ability Score 10) person to grasp, and the smarter/wiser you are the more complicated spells you can comprehend and harness. It seems intuitive me, but if it doesn't to you and your players, I say house-rule away.