Are you able to use the same Ability Score as a Source and Bonus?

Question

I have a specific question about this FAQ through example.

The FAQ states that you cannot apply bonuses from different sources that apply the same ability bonus; for instance, you could not add your Charisma to a Save twice using the Paladin's Divine Grace and Swashbuckler's Charmed Life- only one instance of +CHA would work.

However, the FAQ seems to specify specifically adding it as two bonuses. My question is are you able to have a (ability) based (calculation) and also add (ability) as a bonus.

For instance, could you use Weapon Finesse with a finesse-able Trip Weapon or Agile Maneuvers to have a DEX based CMB and also add DEX as a bonus to Trip from the feat Fury's Fall?

There may be other examples, but that's the one that comes to mind. Citation preferred.

Answer 1

What you describe as base is still defined as a bonus under the rules. So the answer is no, you cannot. Your example is clear when it says that both abilities are adding the dex modifier as a bonus on your CMD

You add your Dexterity bonus to your base attack bonus and size bonus when determining your Combat Maneuver Bonus instead of your Strength bonus.

When making a trip attack, add your Dexterity bonus to your CMB.

Though they could be argued to be considered different sources being two different feats, the source of the bonus is your dexterity ability, not the feats. The bonus is typed as a Dexterity bonus, and as such, can't stack with itself.

However, there are specific abilities that allow you to add the same ability modifier bonus twice. Those abilities are exceptions to the rule clarified on the FAQ. Usually, the type of the bonus must be different so it's considered another source.

Examples:

• Guarded Hearth (Home cleric subdomain): Add wisdom as a sacred bonus to saves.
• Whispering Spirits (Spiritualist Investigator archetype): Add wisdom as an insight bonus to your AC and saves for 1 minute.

Answer 2

No, you cannot, at least for those two cases.

Agile Maneuvers and Weapon Finesse both have you add your Dexterity bonus to a roll instead of Strength (Weapon Finesse uses the word “use” but how do you “use” a bonus? You add it). Fury’s Fall then has you add your Dexterity bonus to CMB.

This leads to trying to add your Dexterity bonus twice to the same roll as an untyped bonus. The FAQ you link prevents this from working.

If you add an ability bonus to something as a typed bonus, then it can stack with another bonus (of another type or no type) from that same ability score.

Answer 3

In complement to the other answers I have to precise that some abilities explicitly allows you to add twice the same ability modifier as an untyped bonus to one roll. For example targeted bomb admixture:

(...) the bomb deals its base damage plus double your Intelligence modifier instead of just its base damage plus your Intelligence modifier.

However you can notice that the formulation specifically allows this to work in that case, and not in your question's example.

The general case is that you can't stack twice the same untyped ability bonus to the same roll, because it's not actually an untyped bonus: among "modifier types" you can find "ability score".