Invisibility and movement through enemy squares

[David_Bross]

If you attempt to enter a square that an opponent is in, you can not without an acrobatics check. Therefore, players with no way to detect invisibility will blindly run through all the squares an enemy could have moved to since becoming invisible with their move action, and if they are stopped from entering a square, have pinpointed the square the invisible creature is in. The only way I can imagine this not working (which I think is the obvious intent given the rules for groping about for the invisible creature) Is for the "opponent" to say "I'm helpless, not resisting the attempt to move through my square", the exact same way people do when allies use the reposition combat maneuver on them.

relevant rules
"A creature can grope about to find an invisible creature. A character can make a touch attack with his hands or a weapon into two adjacent 5-foot squares using a standard action. If an invisible target is in the designated area, there is a 50% miss chance on the touch attack. If successful, the groping character deals no damage but has successfully pinpointed the invisible creature's current location. If the invisible creature moves, its location, obviously, is once again unknown."

"Opponent: You can't move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares."

[Quantum Steve]

There's only two ways to move through an enemy's square: Acrobatics, and Overrun.

You can always choose to move out of the way of an overrun, so...

[Lamontius]

hee hee until the invisible hiding thing uses a move action and then readies an action to move again if another creature enters one of its threatened squares

[David_Bross]

yes but they can't make an overrun against an opponent of the same size, its why I went with acrobatics and them intentionally failing the attempt.

Regardless, I've been with at least three distinct groups who have used this tactic and I'd appreciate an FAQ on this, because I think the intent of the rules is fairly clear to disallow this.

[DM_Blake]

I have had players try this. I don't allow it for the following reason:

5' squares are quite big. It's hard to tell on a battlemat, since most figures have a large base, protruding shields, weapons, or other items, etc. But I have been in elevators that were barely 5'x5' and we still got 5 people in there without anyone touching anyone else. I have also marked off a 5' square on my game room carpet with duct tape and told all my players to stand in it. I got 6 players in it once.

A 5' square contains 25 square feet, and a person only takes up about 4 square feet, unless they are huge or obese. So even though Pathfinder says each person requires a 5' square, they don't actually "fill" that square. In fact, they only fill about 4 square feet of it, leaving 21 square feet completely empty.

This is why your allies can move through your square if you let them - they temporarily take up about 4 square feet and so do you, that's only 8 of the 25 square feet in your "space".

Sure, sure, during combat everyone is moving around, ducking, sidestepping, twisting, dodging, using much more than their piddly 4 square feet. That is why combatants need a 5' square - but they still don't "fill" it.

Back to invisibility:

The rules state that to "grope" for an invisible creature, you MUST use a standard action and pick an adjacent square and make a touch attack. Why? Because you're not just reaching into the space. You're swinging your arms back and forth, high and low, essentially trying to fill all 25 square feet with your "groping" arms - actually, your "groping" around most of the 125 cubic feet in case the enemy is ducking or squatting.

This means that if you're simply moving through squares, you are not "groping" because that requires a standard action. And while you move through a square, you only occupy about 4 square feet, or roughly 1/6 of that square. If there is an invisible enemy there, also medium, he occupies about 1/6 of the square and he can see you and make sure he's in whatever part of it you are not moving through - exactly the way your allies can let you pass through their squares.

RAW? Yes - because "groping" REQUIRES a standard action to search one square. All the rest is just my explanation for why merely zipping through a square is not "groping".