Multiple stat substitution question.

[Saldiven]

Here's an example which illustrates my question.

1st level Inquisitor with the Heresy Inquisition and the Student of Philosophy Trait. These grant the following:

"Righteous Infiltration (Ex): You use your Wisdom modifier instead of your Charisma modifier when making Bluff and Intimidate checks."

"You can use your Intelligence modifier in place of your Charisma modifier on Diplomacy checks to persuade others and on Bluff checks to convince others that a lie is true."

So, when making Bluff checks, this character has abilities that substitute either/both Int and/or Wis. Obviously, the character wouldn't get both Int and Wis. Does one take precedence? Does the character get to choose? Are the rules silent on this?

[DM_Blake]

Just pick the better of the two. The character essentially has both abilities so he can pick which one to use, but not both, so always pick the best one.

[Hyamda]

As worded, Wisdom substitute your Charisma, whatever you may do as righteous Infiltration clearly indicate. Student of philosophy on the other offers the possibility of using Intelligemce on specific part of the Diplomacy and Bluff skills. Whenever you would use one those skill for the indicated purpose you can then decide if you use your Wisdom or Intelligence at your convenience.

[Saldiven]

Cool. Choosing either one seemed to be the most appropriate option, but I couldn't find anything in the CRB that specifically states that.

[Joe Homes]

Disclaimer: not a dev, don't know what I'm talking about, commenting only as a GM.

I'd say that the character has a choice of using either Wisdom or Intelligence for each separate Bluff check (assuming the Bluff check is to convince others that a lie is true; if not, she uses Wisdom).

Righteous Infiltration seems to replace the base statistic wholesale; you can't actually choose to use your Charisma modifier any longer. From now on, the default is Wisdom.

In the second ability, the word "can" is important. This implies that each time you attempt one of the described checks, you choose whether to use this power or not, and use Intelligence instead of your default base statistic (which is Wisdom, not Charisma).

I think it's nonsensical to read the second power as replacing ONLY Charisma, or to say that if you wouldn't use Charisma for that check, you can't use this power. Rather, I think the "in place of your Charisma modifier" clause is included in this rule to clarify that you don't add both your Charisma AND Intelligence modifiers when calculating your result (as I'm sure many players would otherwise be tempted to do). That sort of thing happens from time to time, where necessary clarifications cause some confusion elsewhere. ROI is definitely a thing... and is actually the exact reason that my job exists, come to think of it.

Anyway, it's not a terribly powerful combination, but could play out well in a few corner cases. For instance, if the character has a higher Wisdom modifier than Intelligence modifier, she will typically choose not to activate her second ability to use her Intelligence modifier; however, if she takes a great deal of Wisdom drain or suffers some other effect that drastically reduces her Wisdom modifier, she is able to use her un-damaged Intelligence modifier on those (relatively specific) Bluff checks.

Also, if she maxed out her Intelligence score, she would want to use Wisdom for most checks, but Intelligence for the specific instances in which she was allowed to.

So, not a great power, but *might* come in handy. Someday. Maybe.

[Saldiven]

The main reason for the combination is to get all the necessary social skills (Bluff, Diplomacy, and Intimidate) off of Cha, which can then be tanked while still being an effective "Face" character.

A first level Inquisitor with a max tanked Cha of 7 could still easily have all the social skills at +5 to +7, without any other Feats, Traits, or Race/Class abilities.