What do you consider the Primary Sources?

[Jowgen]

I've noticed that whenever a discrepancy between books is brought up, someone tends to cite the "Primary Sources" text from... the actual source escapes me at this moment, but it specifically mentions the DMG (for rules) and the Player's Handbook (for PCs), which I have found to result in people often ruling in favour of whatever those two books say, even in cases where a newer book specifically claims to supersede a prior (e.g Rules Compedium trumped by DMG).

What I'd like to know is how everyone feels about the Primary Sources issue, as to how you interpret the rules themselves and what books you consider to be the "Prime" in regards to certain topics.

[Curbstomp]

It seems to me that it is rules-access and DM dependent. I, for example, have access to an updated 3.5 DMG and it trumps the non-updated one. But a lot of rules discussion is something that takes place at an individual table. Some spells and feats have been printed 4-5 times. Which version do we use? You might use the last one printed, or the last one printed in a book that your group has a copy of, or you might select the one that seems the most balanced, or even the one that is the most busted. It really depends on the group you are playing with and the DM.

[OldTrees1]

I consider:
The Rules Compendium to be the Primary Primary Source (despite this being false*)
PHB 3.5 to be the PS on character generation (including NPCs)
DMG 3.5 to be PS on magic items and campaign mechanics
MM 3.5 to be PS on monsters
Libris Mortis, Lords of Madness and Draconomicon to be PS on their creature types (until overruled by the DM).

*WotC wanted the Rules Compendium to trump core(as said in RC) however they decided to reprint core after printing RC. They overlooked their "most recent update" rule.

[Jeff the Green]

Do you mean RAW or the heuristics we actually use? RAW, I tend to agree with people who say that it means the first book that lays out an actual foundation on the subject. (Yes, this does make the Rules Compendium entirely irrelevant.) So the DMG, which set out rules for PrCs, trumps what CW has to say about them. (Though they still affect the ones in the book, as specific trumps general.) It also means that the XPH trumps anything the MM says about psionics, since it's the one that lays a foundation for the concept, while the MM just tangentially says that some spell-like abilities are psionic but doesn't say what that means.

My own heuristic is the same, except when the authors clearly intend to rewrite a rule for the entire game. So Rules Compendium is back in, but CW still doesn't affect other books. (Though that would also fall under my Rule 0.5: Any rule or combination that creates infinite loops or quantum superpositions is out, and any player who tries to use them is called a moron.)

[sideswipe]

prime material, to me that says books that should always be allowed no matter the campaign, unless you are specifically running a PHB campaign (bad idea)

PHB
DMG
MM1
Complete - adventurer, mage, arcane, divine, champion, scoundrel
PHB2 ?
Rules compendium (what my groups use as the definitive rules set)

though in my campaigns i run i allow all first party non campaign specific books as a norm, campaign books are allowed as long as i am asked, WOTC web stuff i would usually allow, third party.... as long as i pre approve it under scrutiny, and homebrew if i like it, along with a few feat fixes.

[Curmudgeon]

Here's the rule:

Errata Rule: Primary Sources

When you find a disagreement between two D&D® rules sources, unless an official errata file says otherwise, the primary source is correct. One example of a primary/secondary source is text taking precedence over a table entry. An individual spell description takes precedence when the short description in the beginning of the spells chapter disagrees.

Another example of primary vs. secondary sources involves book and topic precedence. The Player's Handbook, for example, gives all the rules for playing the game, for playing PC races, and for using base class descriptions. If you find something on one of those topics from the Dungeon Master's Guide or the Monster Manual that disagrees with the Player's Handbook, you should assume the Player's Handbook is the primary source. The Dungeon Master's Guide is the primary source for topics such as magic item descriptions, special material construction rules, and so on. The Monster Manual is the primary source for monster descriptions, templates, and supernatural, extraordinary, and spell-like abilities. This appears in Errata files for a bunch of books; this one is from Book of Exalted Deeds, the first one (alphabetically) in my directory of all downloaded errata.

There are only three primary source books. Rules Compendium's authority is entirely self-granted, and (by its own stipulations) all its rule changes are backed out by the Premium core books (as Curbstomp pointed out).