Ethereal solid / incorporeal?

[schreier]

Going through a scenario in a stronghold with ethereal solid walls. The maneuver one with shadow allows you to become incorporeal but does not mention anything about the ethereal plane (nor does the incorporeal description in the srd mentioned ethereal)

Is an incorporeal being always on the ethereal plane?

[Jowgen]

Incorporeal (https://www.dandwiki.com/wiki/SRD:Incorporeal_Subtype)and ethereal (https://www.dandwiki.com/wiki/SRD:Etherealness)are two different things, that sometimes coincincide. See the links.

[Segev]

Going through a scenario in a stronghold with ethereal solid walls. The maneuver one with shadow allows you to become incorporeal but does not mention anything about the ethereal plane (nor does the incorporeal description in the srd mentioned ethereal)

Is an incorporeal being always on the ethereal plane?

As Jowgen says, they're different things.

Incorporeal creatures can't go further into a surface than "adjacent to the exterior," which is why ghosts and such that are meant to go through any thickness of walls also can go to the ethereal plane. Being on the ethereal plane lets you see into (and often be seen on) the material plane, but most objects just aren't there, so you can pass through them. If something has "ethereal stone" present, that means the stone is present on the ethereal plane. Whether there's a corresponding thing on the material is another question.

Dungeons and strongholds with "ethereal solid walls" almost assuredly have the ethereal walls and the material walls overlapping. The idea is that you can't use the ethereal plane to penetrate its walls.

If the walls are thin enough that you can be adjacent to both sides of them while inside them, an incorporeal creature can still pass through them.

[Necroticplague]

Is an incorporeal being always on the ethereal plane?

No, being ethereal and incorporeal are separate states. It's possible to be both, but this both isn't the default assumption, and probably means something different than what you're thinking of by asking.

[Ramza00]

Ethereal you are on a parallel plane, you can see the other reality like you can see a reflection in a mirror, but you are not on the material plane. You have special attacks or spells to cross the plane gap and if you do not you are just an observer.

Incorporeal creatures are on the material plane, they just lack bodies made of matter.

[Thunder999]

Ethereal and incorporeal aren't usually related (though ghosts are a mix of the two, which is where many misunderstandings start).

Incorporeal means you lack an actual body and can therefore pass through objects, but you must remain adjacent to the surface, so you can only go through things as wide as your own space. You also get lots of nice defensive abilities.
Incorporeal creatures have no issues affecting corporeal creatures.

Ethereal creatures are anything on the ethereal plane, it overlaps the material and you can see the material plane from it by default (creatures on the material plane can only see onto it with spells like see invisibility), most objects and creatures only exist on the material plane, so you can effectively pass right through them.
Ethereal creatures can't generally affect the material plane though a small number have special abilities which do.

Those ethereal walls wouldn't necessarily stop incorporeal creatures if they're just walls that exist on the ethereal plane, but force effects do work on both ethereal an incorporeal creatures (as long as you remember to have force floors and ceilings as well as walls)

[Crake]

its worth noting that even if there's a solid object on the ethereal plane, an incorporeal creature who resides on the ethereal plane can still pass through it, because while ethereal and incorporeal are two different things, it IS entirely possible to be both at the same time. A shadow on the ethereal plane for example, is both incorporeal and ethereal, and could pass through an ethereally solid wall of sufficient thinness just as it could normally do on the material plane.

[Bohandas]

Dungeons and strongholds with "ethereal solid walls" almost assuredly have the ethereal walls and the material walls overlapping. The idea is that you can't use the ethereal plane to penetrate its walls.

Unless it's supposed to be a labyrinth where changing planes at the right point is part of solving the maze.

Also, although it is implied, it nonetheless bears mentioning that ethereal walls only help with defense if you also have ethereal floors and ceilings.