Can you Plane Shift to the plane that you're on?

Question

What happens if you cast plane shift and then attempt to shift to the plane that you're on? I can think of a few reasons this might happen in-game:

1. For some reason, the PCs don't know what plane they're on, so they try to plane shift to their current plane.

2. PCs who don't have teleport memorized find themselves in over their heads, and want to use plane shift to escape from their current location (but don't actually want to go to another plane).

I can think of a few possible results:

1. The spell functions as normal. The targets immediately move elsewhere on the same plane, arriving 5 to 500 miles from their intended destination.

2. The spell fails without explanation, so PCs in situation #1 still don't find out what plane they're on.

3. The spell fails, but it is somehow obvious why. PCs in situation #1 find out that they're already on the plane they were trying to go to.

Are there any possibilities I'm missing? Has this issue been addressed explicitly in any edition of D&D or Pathfinder? What actually happens in Pathfinder?

Answer 1

You cannot shift to the plane that you are on.

If you look at the spell description, it's pretty clear about this:

You move yourself or some other creature to another plane of existence or alternate dimension.

Emphasis mine. The exact same text exists in both 3.5 and Pathfinder. In order to use plane shift, you have to be transporting yourself to a different plane.

This basically works like result 2; if you're on Arcadia, and you try to plane shift to Arcadia, it doesn't work. The most likely reason is that you are trying to shift to a plane you're already on, but you might instead be failing for some other reason: a restriction on planar travel from your current location, some kind of protection on the location you're trying to shift to, or something else.