Ovinomancer said:
Do the fictional people in your world know what the fighter class is and what that means? Do they know what the monk class is and what that means? Do they know what the XXX class is and what that means?"
For me, usually, they don't know them as "classes," but they know them as things with meaning, to varying degrees. They know that someone with supernatural martial arts skills (ie, "I can punch a dragon for 1d8 damage!") has been trained by people who know how to use those skills, and such people gather in certain organizations that occupy certain locales in the world. They know that someone who is keenly accurate with a blade (ie, "I crit on 19-20") is associated with cadres of warriors known to hone skill to that degree, who occupy certain roles and locales in the world. They know that a nature-priest who transforms into beasts (ie, "I have Wild Shape and the Druid spell list!") are linked to groups of people in the world that can do that.
And since the mechanics are expressed in the fiction (meaning, someone who crits on a 19-20 IS exceptionally accurate with their attacks, someone who punches dragons for 1d8 damage IS using supernatural martial arts skills), someone with those mechanics should also be linked to that fiction, IMO.
That's why, for me, in general, classes are primarily about fiction, not about mechanics. The mechanics are there to support the fiction. If you'd like to use the mechanics to support some other fiction, it's generally a pretty awkward fit unless you hand-wave or ignore where it doesn't fit. It's fine to do that, but I don't find it very satisfying - I prefer when my mechanics and fiction work together to build on each other, not when they're fighting because they don't really work. Think of your fiction first - the character you want to play. We'll then come up with how to represent them doing those things mechanically.
Ovinomancer said:
I'm not set on proscribing the only fiction that a fighter can be, but, realistically, if you're interested in specializing in casting spells, fighter's probably not a good mechanical fit for you.
I think one thing that might help to illustrate my point: that's a distinction in
the fluff, but it's not a distinction in
the mechanics.
Nothing, mechanically, says I can't use a longsword and a shield and re-fluff it as "a magical wand that projects a field of force that I slash with and my other hand can be used to make powerful, nearly instantaneous magical defenses made of the bones of my enemies with a simple gesture." There's nothing in a bow that says that it can't be "a powerful bolt of eldritch energy sent screaming through the air into the flesh of my foes."
I can also do it the other way around -
magic missile is my superbly accurate archer taking time, aiming, and letting an unerring arrow hit.
Burning Hands can be my character spitting some hard alcohol through a torch.
Mage Armor can be, well, regular armor.
Faerie Fire can be my character pointing out the flaws in enemies' defenses.
4e's a pretty good example of this thought process in practice - a level X ability is largely on par with other level X abilities, mechanically. You have your "martial fireballs" and your "magical multi-attacks" and the like. I find 5e generally shies away from this, though.
Anyway, the same thought that goes into you dividing magic from martial is the same thought that goes into "Monks are a specific thing," just more deeply applied.
And it's more deeply applied, for me, because it leads to a much more developed play experience, ESPECIALLY for newbies. Having monks be a specific thing is a frequent reminder that you are playing a fantasy character in a game of make-believe, not a set of stats.
Which isn't to say that a more abstract view is bad, just that I find it makes you think about a character more in terms of mechanics than in terms of fiction, which is not the most fun place for me to play D&D at.