We're not sure how to handle certain things concerning incorporeal creatures.
incorporeal (trait) An incorporeal creature or object has no physical form. It can pass through solid objects, including walls. When inside an object, an incorporeal creature can’t perceive, attack, or interact with anything outside the object, and if it starts its turn in an object, it is slowed 1 until the end of its turn. A corporeal and an incorporeal creature can pass through one another, but they can’t end their movement in each other's space.
An incorporeal creature can’t attempt Strength-based checks against physical creatures or objects—only against incorporeal ones—unless those objects have the ghost touch property rune. Likewise, a corporeal creature can’t attempt Strength-based checks against incorporeal creatures or objects.
Incorporeal creatures usually have immunity to effects or conditions that require a physical body, like disease, poison, and precision damage. They usually have resistance against all damage (except force damage and damage from Strikes with the ghost touch property rune), with double the resistance against non-magical damage.
anchored incorporeality 37
In particular, we have a ghost in the party (as per the archetype in the Book of the Dead).
You also gain the incorporeal trait, as described on page 218, except you can’t pass through solid objects unless you select the Pass Through feat.
(Ghost PCs gain the ability to affect the corporeal, so this question isn't about that.)
The question centers around
a corporeal creature can’t attempt Strength-based checks against incorporeal creatures or objects.
Aren't Strength-based attacks Strength-based checks? But ghost monsters don't have any immunities listed. They merely have a resistance with an exception carved out for ghost touch. And while a ghost PC doesn't start with such a resistance, they can gain one.
So, ignoring the damage forms specifically called out (force, ghost touch), what affects an incorporeal creature?
- Dexterity-based attacks?
- Strength-based attacks?
There's a strong likelihood we'll encounter incorporeal monsters or even create them, so the question isn't limited to ghost PCs.