All verbage pulled from PRD
Skills chapter under Stealth:
"If people are observing you using any of their senses (but typically sight), you can't use Stealth. Against most creatures, finding cover or concealment allows you to use Stealth."
Combat Chapter under Concealment:
"Concealment and Stealth Checks: You can use concealment to make a Stealth check. Without concealment, you usually need cover to make a Stealth check."
CRB Glossary under Invisibility Condition:
"The ability to move about unseen is not foolproof. While they can't be seen, invisible creatures can be heard, smelled, or felt.
Invisibility makes a creature undetectable by vision, including darkvision."
Combat has started, everyone is aware of everyone. An enemy casts invisibility. He now:
A) Uses his move action to stealth since he has concealment and concealment says he can stealth?
B) Just has total concealment, and can not stealth without something else like a bluff for distraction because everyone is aware of him and is "observing" him with their ears?
He takes option A, concealment is a specific rule that overrides a generic rule such as stealth which states that simply listening to/for someone you're aware of makes it impossible to stealth.
My opponents stance:
He takes option B, if you're aware of them at the start of their turn in any way, he can't stealth, ever.
Does anyone have anything concrete that supports either stance? Developer opinion, rules monkeying, obscure book knowledge, etc?