I see Mearls' comments as no more or less valid than any other DM which is to say that's how he rules it as his table. In this case, I don't rule it that way because it effectively kicks the meaningful decision-making back to character creation rather than keeping it during play. I want the trade-off as suggested in the Basic Rules (page 65).
He helped write the rules. He knows what they meant when they wrote it. There would be no concept of Passive Perception if it wasn't for him and his team. So what it is and how it is used means a little more from him than coming from a random DM. Anyone can choose to change the rules and I'm saying there's nothing wrong with running it differently at your table. But I'm talking about the way it was intended to be run by the creators.
As for a trade-off, I still see that there IS a trade-off. When you make your character you trade off being good at one thing in exchange for being good at Perception. You will be less good at other skills, and possible your spells, attacks, or hitpoints because you got better at Perception.
p.65 doesn't really talk about tradeoffs in the way you at thinking about them.
Which is why the DM takes these things into consideration when deciding whether the outcome of the situation is uncertain enough to warrant a check (passive or otherwise), whether the check has advantage or disadvantage, or whether the outcome is certain i.e. the character does or doesn't notice the threat (no check).
Correct. The specific circumstances have to be considered. But the consideration should be "Do the people in question have ANY chance to spot or hear the danger?" If so, they can use their PP. If they have no chance(because maybe the sound is so quiet and they are too far away to possibly hear or because the creature can be seen but not heard due to a silence spell), then you don't allow them to use it. That's fairly straightforward.
But what you were suggesting is that as soon as anyone takes any actions whatsoever except looking for threats that their PP immediately turns off and they can neither see nor hear anything hidden. That's not the same thing at all.
The rules don't require us to do anything. The rules serve the DM, not the other way around. They come into play when the DM says so to resolve uncertainty that the DM establishes.
The rules don't "require" anything, I suppose. They suggest a lot of things. Most of them are pretty much necessary for play. Like everyone needs to create a character, there needs to be a DM, and so on. But let's assume all the suggestions are equally important. So, the rules then "suggest" that you need to roll a stealth check opposed by the PP of everyone who has any chance of hearing or seeing you.
The DM is free to rule that a certain character has no chance to hear or see something. But there should be a good reason why there is literally zero chance. Wax stuck in someone's ears: Sure. They are searching some drawers? Nope. Their ears continue to work.
The rules would seem to suggest otherwise. First, and again, the DM decides whether a situation is uncertain enough to use mechanics - he or she might decide on automatic success or failure instead. As well, the section you're referencing doesn't mention "exploration turns" and earlier in that chapter it suggests that pace and travel takes place over minutes, hours, and days, not just hours as you say. A slow pace is 200 feet per minute. One can imagine that searching a 20 x 20 chamber for secret doors might include walking the perimeter of that room thrice (240 feet, just over a minute) while poking around. That's a task being performed repeatedly and thus may warrant a passive Perception check.
Here's a little background, in case you didn't play the playtest. That entire section was an optional module during the playtest. They created a system of "exploration turns" where if you were travelling long distance such as on an overland map, you could then break out those rules and ask people what they were doing as their "exploration turn". The rules were designed specifically for travelling overland across the wilderness. But the rules said you could possibly use them when travelling over a large unexplored area of cavern or dungeon rather than dealing with each room one by one. The name "exploration turn" got removed from the final draft but the concept stayed almost precisely the same, it was just reworded slightly.
In the final rules, that entire section is under the major heading "Activity While Travelling". Those rules are only meant to be used while travelling over longer distances. The idea being that whenever multiple minutes pass while going from one location to another, you could switch to a more abstract way of playing and instead ask people for a general idea of what they were doing over those couple of minutes/hours/days.
The text says "Characters who turn their attention to other tasks
as the group travels are not focused on watching for danger"
The key here is that these rules apply when moving from one room to another across multiple minutes worth of dungeon or when travelling from one city to another. They don't apply when you are inside a room and searching it for treasure.
Even with these rules, it is assumed that anyone not taking one of the 4 actions listed on page 65(or something the DM allows) ARE on the lookout for danger. The default action is "watch for danger" while travelling(this includes while doing all of the standard things you need to do while travelling: eating, resting, using the washroom and so on).
The text at the beginning of this section says "As adventurers travel through a dungeon or the wilderness, they need to remain alert for danger, and
some characters might perform other tasks
to help the group’s journey." I think this is key. The idea of this section is that when travelling a distance you are always considered to just be walking and keeping an eye on your surroundings. But you might be doing something to help the party's journey(such as mapping, tracking, or foraging) that will distract you enough that you won't get your PP while travelling. But the actions in question are done over a period of hours. No one forages for food for a round or a minute. No one maps for a round or a minute. It is an action you take while exploring a large area.
The way the game is written is that it assumes when they get into a room and start searching it for traps and hidden doors that pretty much all of them stop what they are doing and focus on keeping an eye out for danger(which is why you tend to keep track of time doing this sort of things in rounds). I would think this especially applies to those searching the room. They are on alert specifically BECAUSE they are looking around.
In addition, it's not uncommon to see DMs struggling with characters that have a very high passive Perception - RPG forums are rife with this sort of complaint. Ruling it the way I suggest takes some of the power away from passive Perception. It means that if a player builds a character with a very high PP, they need to actually be the guy who is keeping watch, standing guard, or tapping with the 10'-pole in order to get the most benefit from their investment. They can't also be the guy who tracks and forages and searches for secret doors (unless it's a ranger in favored terrain) while still picking up on every hidden trap or monster. This makes it a meaningful choice during play and helps with ensuring equal contribution throughout the party.
Here's the real problem. I agree that PP can ruin a lot of things. That's precisely why I'm interested in this thread. The problem is that as written, anyone with a high PP immediately notices ALL traps the party comes across without needing to say anything or roll anything. This can be very frustrating. What's the point of using traps if they don't do anything because the party can avoid them all. What's the point of using hidden doors if they are always found?
This was brought up during the playtest when they said they would be adding Passive Perception back to the game(since it wasn't in the earlier playtests). Mike Mearls said that they had solved this because in the final version of the rules secret doors and traps would have a stealth skill and you'd roll the stealth skill and compare it to the passive perception of the PCs. This way there would still be some variation. Sometimes a trap would roll high and the PCs would encounter it, even if someone had a high PP.
Everyone was satisfied that a legitimate solution to the problem was found. Then the final rules came out and there was no sign of the rule where traps and secret doors rolled.
So now we are having this conversation because people are confused as to how to solve this problem. Some adventure writers solved in by including a higher DC for passive perception than if someone specifically said "I search the wall for secret doors". Some adventure writers decided to have secret doors that could only be found using Investigation, which implied you actually had to investigate and couldn't spot it passively.
Mearls, as you can see above, still believes that the final rules say that PP is on all the time and lets you spot all traps and hidden doors you come across without rolling. But he has not provided us with a solution to the problem it creates when someone has a really high PP.
I'm not saying your solution is necessarily a bad one. It is one way around the problem created when you follow the rules precisely as written. But I think there needs to be an "official" solution to this problem so that adventures that come use the same system and each DM you come across will use the same system.
Another example: My rogue, Chuck Dagger, has a PP of 20 at 1st level. You could almost see the DM's dismay when realizing this. But as I explained to him, look, if I'm doing anything other than keeping watch for hidden threats, it simply doesn't apply. So when I'm going down the corridor looking for secret doors, I know that I could run afoul of a trap or monster.
Here's where I see the major problem. No one will every convince me that looking around closely to everything around me to see if there are signs of a secret door would suddenly make me unable to spot hidden monsters.
If a DM told me "A spider climbs down the wall beside you and attacks you, immediately surprising you because you were distracted and therefore couldn't see it" I think I would be incredulous. I think this conversation would go like this:
"What do you mean, distracted?"
"You were looking for secret doors, so you didn't have any chance at all of spotting the spider"
"Wait...I was looking at the walls to see if there was a secret door as we walked down the corridor."
"Correct."
"Then my eyes were open and looking precisely in the direction the spider came from. I was watching explicitly for things out of the ordinary."
"Not exactly. You were looking for secret doors. Not spiders."
"So, if I'm looking for my pen on my desk, my iPad sitting next to the pen becomes invisible?"
"Correct."
"...Maybe I shouldn't play this game...it's stupid."
As I say above...there's all sorts of reasons to rule that a certain character can't use his PP to spot something. But those circumstances require both the eyes and ears of a person to be occupied with something that would completely prevent them from detecting a hidden threat or they have to be travelling and have chosen to take one of the 4 actions to help the group travel.
Even the circumstance where a character is foraging seems to be kind of a stretch in terms of "turning off your PP". I mean, keeping an eye out for food while you travel doesn't seem like the kind of thing that should stop you from noticing an ambush. But I've always rationalized it that since we are abstracting turns that are hours or days long that your character is spending time collecting berries at precisely the moment you are ambushed. You instead get another benefit instead of adding your PP: You get free food. If the group decides to bring their own food with them, that just means more people are keeping a closer eye out.
That still rubs me the wrong way, but I'm willing to tolerate it.
