@Ghost said in PC vs Player Assumptions:
If you are playing a role, then should your decisions for the character be based entirely from the perspective of the character itself?
This is a matter of personal choice.
I have been able to solve this issue by focusing on perception/knowledge rolls to help feed information or determine what the PCs know. This leads to successes and my players have stopped trying to "guess what the GM is up to" and now focus on "the PCs solving the puzzle".
This is a matter of GM fiat. This is unrelated to the dilemma identified, which is not really a dilemma in my opinion. No matter which way a player decides, it is a matter for the GM to decide how success on tasks shall be determined and how conflict will get resolved.
If you, the GM, want a player to roll to see if his character knows not to hit a rust monster with a sword, you have the right to ask; if otherwise, then the player decides that outcome. If the player complains that her character knows not to hit the rust monster with a metal weapon, and that she should not have to make a roll, you, the GM, can determine if the proffered explanation is sufficient or not.
Not really seeing a problem, sorry.

