This is an Old School attitude.
Take a look at the way things began with OD&D. You had three (3) Main Classes to choose from: Fighting Men, Magic-Users, and Clerics. The first one hits people and wears stuff to help them not get hurt when they get hit in return. The second one uses spells and isn't allowed to wear bulky, restrictive or unfashionably metallic stuff like armor. The third one gets to hit people, cast some spells, wear some armor, and serve a higher power.
When you only have those three options to work with, you had best come up with a little bit more than just "I'm a fighter. Ugh." or "I'm a magician. Please don't hit me." or "I serve the great god Utumnovax and you shall all serve me or die under torture." Oops. The Cleric got a little rambunctious, but then she had the opportunity to watch the other two slobs blow their chance at truly defining themselves as something more than stock stereotypes yanked off the the same shelf in the backroom where we tend to store the cliches, bad ideas, really bad ideas and
Characters are essential to the whole RPG experience. Nine-tenths of any rule-set is devoted just to sorting out how to make the little darlings as special as can be, loading them up with all sorts of powers, feats, talents, flaws, quirks, multiple-pages of detailed backgrounds, portraits--oh, sorry, wrong edition. I skipped my coffee this morning. Probably a bad idea.
Three Classes is a bit restrictive for most people, even Gygax went and plopped the Thief into the mix with Supplement One: Greyhawk. And NO, I do not count the Elves, Dwarves, or Hobbits as Classes despite what the Big Guy says--they are still pretty much Fighting Men, only in strange costumes like aliens in Classic Star Trek, and they get some minor bonuses for being somewhat specialized or different. That's how I see the rules, that's what I have observed in terms of how others have handled them back in the day, and while I do not approach things in that manner, personally, it is one interpretation of the core rules that still seems to infect people's attitudes to this day.
As far as I'm concerned, the Thief, just like the Races-as-Class, are all variations on the Fighting Man. And for the sake of the women in the audience I will drop the inaccurate and inappropriate 'Fighting Men,' for the simpler and less sexist Fighter. I know, I know; sheerest heresy letting women into the fragrant fraternity of dice-rolling fat-beards, but by all means if you have a problem with it please feel cordially invited to go fuck yourself.
So, back on track, Three Classes has been ricocheting in my head almost as perniciously as that damned Rick Astley song video that comes up when you get Rick-Rolled by someone who just learned about the very cutting edge of 1990's humor just yesterday. I know that even OD&D morphed into a system that used other classes, but when you look through Supplement Two: Blackmoor, or Supplement Three: Eldritch Wizardry, all the supposedly "new" classes are pretty much just variations and mutations of the Three Core Classes. Not the most terribly ground-shaking revelation, I admit, but I'm not engaging in penny-ante psycho-archaeology here, I'm mapping out my own process and peeling back the assumptions underlying the choices that lie at the heart of OD&D with the express intent of seeing what lurks down in those fetid bowels of this formerly well-trod path and following things back to the very roots of the game. By going back to the source itself, the well-spring from which OD&D was originally derived, I can then make different choices and pursue different objectives as I work my way back up and out of the cavernous depths where lies Mymir's Well, as it were.
Three is a good number. I like Three. When I was running my Xembor D20 campaign I had mashed all the Classes down into Three Primary Classes that held all sorts of options for specialization as direct and explicit parts of those Classes. I boiled it all down to Tool Users, Skill Users, and Spell Users. It made sense on paper, and it allowed me to develop a batch of NPCs and even run a few scenarios before that particular group fell apart. The idea still nags at me, and coming back to the OD&D rules for some inspiration has been very interesting. The notion of using only Three Classes is a good idea to build off of, a good place to start. Maybe I'll have to adjust things as I go along, but for now I'll try to stick with the notion of boiling it all down to Three Core Classes.
Ah, and this is where we run into the shimmering green iceberg. How can we discuss Classes without knowing how we will be handling Attributes, or knowing the most basic underlying principles and assumptions of the Setting?
I shall return to this thread once I have addressed the not so little matter of how I want to deal with Attrributes (which handily deals with skills/feats/powers/spells all in one nifty package), and it is time that I gave you all some more explicit description and illustration of the Setting of Riskail, besides the fiction that is accumulating over at the companion blog.