Guild Metaphysics

It seems that in many Role-playing games and their tabletop/MUD equivalents -most of them as copies of prototypes already struck and minted in D&D- the playable classes tend to follow quite a predictable pattern. We can state that all guilds fall into one of the two main and general types, from which they afterwards branch out: they are either Fighters or Magicians.
As it seems, the names are quite self-evident and descriptive. Fighter classes will focus on weapons, armour and general fast-and-evident killing methods, at which they'll probably be more profficent than anybody else. As for Magicians, they tend to rely, on the contrary, on slower and more spectacular ways of dealing with their foes, and unconventional protections.

This general set can be further subdivided into four sub-classes, two for each branch. So, the Magicians can be either of the Priest type (they use 'divine' or supernatural, god-sent magic) or of the Wizard type (they use 'profane', or natural magic), with many more possible sub-branchings, depending on the different gods and their characteristics, and in the different classes of magic and magic practitioners. And Fighters can be divided into Warriors (usually very strong, holders of huge weapons and wearers of heavy armour) and Dodgers (they rely more in fast movement and dodging for their protection, and tend to use light weapons, like daggers, and hiding-and stabbing attacks).

This would be the 'pure' set of classes generally found everywhere. Each class tends to relate to a specific stat as its main and most important base. With stats and guilds, then, we can develop the following correlations:

Strength -------------------------------------- Warrior
Dexterity -------------------------------------- Dodger
Intelligence ------------------------------------ Wizard
Wisdom ---------------------------------------- Priest

The desire to merge the best of two or more classes (easier to do in some worlds than in others) generally leads to a development of 'mixed' classes, even if they are not as proficient in the branches as those who choose the pure. Notorious examples would be Paladins (Warrior-Priests) and Wizard-Warriors.

When applying all this to the Discworld, we find it generally fits quite well. We have all the 'pure classes': Warrior Guilds (Barbarians, Musketeers, Samurai...), Dodger Guilds (Assassins, Thieves), Wizard Guilds (Witches and Wizards) and Priest Guilds.

There doesn't seem to be a priori, despite specializations, any of the mixed categories. But I'd say that's the case because the system is less rigid here than in other places. That is to say, with the exception of a few (albeit important) guild-only skills, an adventurer in the Discworld can learn almost anything (there are some exceptions, though: Wizard classes can't practice any faith, 'priestly' skills. It would seem logical for priests not to be able to practice magic, but that isn't the case). Indeed, I'd say the system rather stimulates mixing up a bit, as at least some of the classes, in a totally pure stance, may confront with some important disadvantages.

Here's also where 'rearrange' comes into. I wouldn't know about other guilds, but it certainly is a wizard's nightmare, as there are no easy solutions. Having a clear idea of the things you want to be good at (and the things you want to be mediocre and damn bad in, as well) helps a bit, but as the Spell tree touches almost every stat there is up to a high degree (in past ages, it seems, all that was required for a good wizard was extremely high Intelligence), even a 'pure' wizard rearrange seems problematic...