A New Explanation of 3 for 1 basis in OD&D

For decades there has been a debate on how to interpret what seem to be rules for ability score modification in Original Dungeons & Dragons (OD&D). Do the actual scores change, or is it just for experience bonus determination? I found a piece of information that leads to a new understanding of the text that finally solves the inherent contradictions and questions the text brings up.

The Text

In OD&D Volume I: Men & Magic p10-11, we get the following text:

Changing Character Class: While changing class (for other than elves) is not recommended, the following rule should be applied: In order for men to change class they must have a score of 16 or better in the prime requisite (see below) of the class they wish to change to, and this score must be unmodified. [...]

...

Explanation of Abilities:

The first three categories are the prime requisites for each of the three classes: Fighting-Men, Magic-Users, and Clerics. [...]

Strength is the prime requisite for fighters. Clerics can use strength on a 3 for 1 basis in their prime requisite area (wisdom), for purposes of gaining experience only. [...]

Intelligence is the prime requisite for magical types. Both fighters and Clerics can use it in their prime requisite areas (strength and wisdom  respectively) on a 2 for 1 basis. [...]

Wisdom is the prime requisite for Clerics. It may be used on a 3 for 1 basis by fighters, and on a 2 for 1 basis by Magic-Users, in their respective prime requisite areas. [...]

...

Note: Average scores are 9-12. Units so indicated above may be used to increase prime requisite total insofar as this does not bring that category below average, i.e. below a score of 9.

 OD&D Supplement I: Greyhawk adds the following text on p7-8:

Strength also aids the fighting man in his ability to both score a hit upon an adversary and damage it. This strength must be raw. i.e. not altered by intelligence scores.

[table of strength effects, among other ability score information]

[Thieves] may use 2 points of intelligence and 1 point of wisdom to increase their raw dexterity score so long as they do not thereby bring the intelligence and wisdom scores below average.

I believe this is all the relevant text from the original sources. If not, please let me know of other relevant text.

Past Interpretations

There are two main interpretations of the text:

The first is to ignore the words "for purposes of gaining experience only" and interpret the text to mean that you are indeed lowering the actual stats and raising actual stats. This is the route that Holmes takes in the original Basic D&D, which at that point was essentially a compilation of the rules for level 1-3 play from the original 3 booklets, and the first one or two supplements. Holmes Basic was edited by Gary Gygax, so this is pretty strong support for this interpretation, but also it literally ignores a phrase, so it can't be right, can it?

The other interpretation is to extend the words "for purposes of gaining experience only" to all stats and essentially make a new prime requisite stat that comes from prime requisite plus whatever adjustments you are able to make, but don't lower or raise any actual scores, just this new prime requisite score. JB argues this persuasively on B/X Blackrazor, but the words "raw dexterity" in Greyhawk really seem to fly in the face of this interpretation.

The Missing Puzzle Piece

In the annotated edition of v5 of the OD&D clone Delving Deeper, Simon J. Bull states the following on page 16, footnote 112:

M&M p10 (Strength): «Clerics can use strength on a 3 for 1 basis in their
prime requisite area (wisdom)» to which the 5th print (Dec. 1975) appends
the following clarification: «for purposes of gaining experience only».

So the phrase "for purposes of gaining experience only" was not in the original release! In fact, according to The Acaeum, Greyhawk was first printed in March 1975, around the time of the second printing of OD&D, multiple printings before the fifth printing when this text was added!

Solving the Puzzle

The simplest interpretation of the text in the first four printings of OD&D and in all printings of Greyhawk is that you are indeed changing actual ability scores. The bit about changing classes requiring unmodified scores is an exception. Same with the bit about Strength in Greyhawk.

So what do we do with this "for purposes of gaining experience only" phrase? Well, there's a few pieces of information to consider. First, this text was added after Greyhawk was released, not before. Second, Greyhawk adds a rule (quoted above) that Strength bonuses for fighters are only for the unaltered score, not the modified one. Third, although the phrase as written refers to Clerics and added Wisdom, it is in the Strength section. Thus, I believe the text was intended to be that Strength raised is for purposes of gaining experience only, as explained in Greyhawk, but they simply made a mistake and put it in the Strength section despite that section being about lowering Strength rather than raising it.

Thus I believe that the intended rule is that you are indeed changing actual scores for all classes, just with these two exceptions: changing classes is based on the unmodified score, and fighter bonuses is based on the unmodified score.

This explains why Holmes Basic, which generally hews quite close to the original text, has the scores actually change despite being edited by Gary Gygax: Holmes either had one of the first four printings that lacked the phrase, or this is the reason why the strength bonuses are not in Holmes Basic, unlike the other ability score stuff from Greyhawk. Gygax probably saw the lack of strength bonuses and was like alright we can keep them out and then this matches.

The One Remaining Problem

In a Q&A with Gygax on EN World, we see the following exchange:

Doug:

[...] I found a reference [in OD&D] under the ability section that stated:

"Clerics can use strength on a 3 for basis in their prime requisite area (wisdom), for purposes of gaining experience only." Likewise, [there] is a comment under Intelligence that "Both fighters and Clerics can use it in their prime requisite areas... on a 2 for 1 basis." Similar comments are made about wisdom for fighting men (counting 3 for 1) and magic users (2 for 1).

What the heck does that mean? That, for instance, clerics can add Wisdom + 1/3 of their Strength to determine their experience bonus?

Gary Gygax:

You got it.

It seemed like a good idea at the time, this substitution enabling the 10% XP bonus to PCs with high abilities assocoated [sic] with but not their prime one, such as the cleric using 3 Str to equal 1 Wis.

DMs didn't think it was a particularly useful rule, so it was dropped.

It would seem that Gygax is saying that the interpretation that does not have ability scores actually changing is the correct one rather than the interpretation that I put forth. However, it is important to note that when these rules were written, there wasn't much explicit use for the primary ability scores beyond xp boosts anyway. Additionally, he is responding in the affirmative, not saying that a different interpretation, such as the one in this post, is incorrect. Lastly, his words as written in that forum post ignore the not below 9 clause. I don't think he is trying to say that in the original game the scores weren't actually modified.

Postscript

tl;dr I think OD&D ability score modification modifies the actual ability scores, and what's meant by "for purposes of gaining experience only" is that when fighters raise strength, they don't get additional bonuses to hit and damage

I don't actually have intimate familiarity with OD&D or Holmes Basic, I just fell down this rabbit hole, so please correct me if I got anything wrong, and I'd love to hear what people think about this!

Addendum

A link to documents from the 1979 court case between Dave Arneson and Gary Gygax was posted to The Ruins of Murkhill. Among other things, it contains some draft material from the creation of OD&D. Here is some text from it:

While every ability is helpful to all the classes of adventurers, one is more important to each. This ability is called their prime requisite. The average score is 9-12. If a player is above or below the average in his prime requisite, his experience point acquisition will be affected and hence his advancement through his class. However, certain non-prime requisite abilities, depending on the class, may help a player overcome a below average score if the player has an excess in that non-prime requisite ability, excess meaning a score above 9. The player can trade off this excess to add to his prime requisite as long as his score does not fall below 9. 

This text is significantly more clear than the text in the final product, and makes it clear that the ability scores themselves are indeed changing: the player is trading off the excess to add to their prime requisite.