All skills? So there are circumstances where just about any skill can be done passively?
Theoretically, yes. It is up to the DM to decide.
I was under the impression that an active skill check was one where the PC was consciously performing a skill while a passive skill check was more of a subconscious thing. Passive Insight representing the 'gut feeling' we all have from time to time, for instance.
Personal interpretation.
Passive skills represent things done on autopilot.
Personal interpretation.
actually, in o5e, according to
crawford himself, your passive perception IS the floor for your perception (22:20 for the start of passive perception, 23:20 for when he starts explaining it's the floor) - the reasoning seems to be the act of perceiving is something you're always doing, and so it doesn't matter if you roll low, since you're always perceiving
Personal interpretation.
Basically passive skills are skills that are used so often by the PC that they become rote behavior. A PC with Passive Acrobatics is someone who has constantly practiced acrobatics in and out of combat to the point where they don't need to consciously perform them. They just do it.
Personal interpretation.
Not saying that you should NOT use your personal interpretations, or that these interpretations have something wrong, but really all of these are just something you are adding to the rules on your own volition.
This is the main text in PHB:
"A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for
a task done repeatedly, such as searching for secret doors
over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster."
Ignore the second usage because that is clearly a meta/out-of-narrative decision of the DM (who could also secretly
roll the dice on the player's behalf to keep the result secret, the DM can but doesn't have to use this option).
The only narrative explanation of a passive check mentioned in the PHB is
repetitiveness of the task. It doesn't mention (un)consciousness, autopiloting, providing a minimum result in general.
Even the interpretation of "you're always perceiving" is misleading. Yes, you are always perceiving
something as long as you are awake, because your eyes are open and your hearing never stops... but you are not necessary always
searching for traps or hidden stuff. Otherwise you could say that you are also always using your muscles therefore you should be granted minimum 10 in all Athletics or Acrobatics, and as you are also always using your mind you should be granted minimum 10 in all Knowledge. If that's how you like playing the game, go for it, just be prepared that you'll remove a large chunk of randomness from the game.
The RAW doesn't imply all this stuff. Again, do what you want, but don't pretend it's automatically implied by the PHB because it's not.
OTOH, the DMG has a bunch of additions (see "Secret Door", "Concealed Door" and "Detecting and Disabling a Trap" sections) which unfortunately do seem to dictate things more strictly, and not in a good way because they do force a certain playstyle while the whole 5e edition was conceived around the principle of... not dictating playstyles. But then fortunately enough, the whole DMG is written with a tone about
helping the DM, so you can argue that the DMG as a whole is more a bunch of suggestions than strict rules. Either way,
rule zero still gives the DM full leverage on whether an ability check is needed in the first place, before you even ask if it's resolved actively or passively, and this is more than enough to wash away a DM's worries on passive checks.
It is also useful to remember that the RAI behind passive checks is a lot more grounded in metagaming than narrative, with the latter being more a post-justification of it. It is primarily meant as a DM tool to avoid a situation where a paranoid player would constantly ask for checking the same thing over and over, such as the proverbial Rogue wanting to check for traps every few steps, possibly to get revenge against a DM herself guilty of placing traps in places too random to guess reasonably. The passive check rule allows a player to get their PC covered by saying "I will
repeatedly check for traps while we are in this area" without worrying about guessing the exact location, and without annoying everyone with a hundred useless rolls (note: this is not the
only method, because a DM who wants to maintain randomness could also simply ask
one active check and say that it covers the whole area).
You can certainly allow your PCs to have passive perception ON for everything, all the time. But there is no reason for another DM to feel forced to consider you repeatedly searching for traps AND repeatedly watching out for secret doors AND repeatedly staying alert for stealthy monsters... another DM can very much say that you have to say what you're doing repeatedly, and there's a limit to how many things you can do repeatedly at the same time, and they wouldn't be playing outside the rules.
It is only when you start adding your personal interpretations, that you bind yourself to consequences, but that's your choice and doesn't have universal validity.
