Pseudopsyche
First Post
I think we can all agree that labels/keywords such as "mage" could be abused or misused to create poor rules. My main point is that they could also have some value. The difference between "is a Mage" and "can cast Magic Missile" is more about granularity than anything else. An Arcane Student feat could just as easily say, "You qualify as a Mage for the purposes of using magic items" as "You may add some spells to your spell list".The distinction becomes functionally meaningless in practice. What falls into the "mage" bucket is essentially arbitrary, without relevance to the characters that people play. At least "If you can cast Magic Missile..." is a clear mechanical and fictional criteria, and it opens it up to a Fighter, Thief, Assassin, Druid, Cleric, or Barbarian who takes a hypothetical "Arcane Student" feat (that gives them a few cantrips), regardless of which class they take.
I mean, why give Character X some advantage or benefit just because they checked the right box at character creation, and prohibit Character Z from getting that same benefit because they didn't? Whether or not you cast the Magic Missile spell might be relevant for whether or not you can use the Wand of Magic Missiles, but it says jack all about HD size, armor proficiency, role in the world, or if you should be able to qualify for metamagic feats.
Both granularities have their advantages. You might say that it makes more sense for a warlock who can cast Burning Hands but not Magic Missile to be able to use a Wand of Burning Hands more easily than a Wand of Magic Missile. I might say that it's simpler and more streamlined for a warlock player who finds a Scroll of Evard's Black Tentacles to remember that warlocks count as Mages instead of having to consult a rulebook to determine if Evard's Black Tentacles is a "warlock spell".
As someone else pointed out, this discussion is really all about abstraction, which is the practice of treating two distinct things as being essentially the same, in some context. I'm not arguing that a Wizard and a Warlock are the same, but I am suggesting that there are enough contexts in which a Wizard and Warlock should be treated as the same, that it's worthwhile to create the abstraction.
If I publish an adventure with the last remaining wand of a long-lost Thassilonian arcane spell, I just want to be able to say that any Mage can use it, instead of having to enumerate specific arcane classes or arcane spells that can serve as prerequisites instead. Or, if you like, any character can use it, but any Mage can attempt to learn the spell.