Twice this week this has come up. Once in a discussion on this board, and once in a discussion with one of my players.
Do you use passive insight in your game? I don't, and I'll give my reasons below, but I am genuinely curious to hear other opinions and arguments for and against. I was fairly surprised that it seems a good number of people believe have come to expect passive insight as a rule.
For sake of starting the discussion, here are the reasons why I don't use passive insight:
Passive checks essentially set a baseline number for your ability checks that is at least average. That means, that a complete failure is impossible. So I avoid passive checks if at all possible, because I believe sometimes you should roll a 1 and bungle an ability check. My one exception to passive checks is perception, because perception is something that is always turned on to some degree while awake, and I've found you can run it to great effect in a game. There is a good amount of control and affecting conditions, such as low light and obscuration, that can place a -5 modifier on perception. This means that even a character with high perception might miss things if the conditions work against him/her.
And of course, passive perception helps reduce the temptation of your players to feel like they have to actively check every single nook and cranny of every room. They know that even if then don't actively check, they are at least somewhat covered by passive perception. It also helps with sneaking situations where the players are sneaking around lackadaisical guards who just have their passive perception scores to rely on, and vice versa.
But passive insight presents a host of problems for me. It sets that baseline number which a character can't roll below, of course. And that presents role-playing and story-telling problems. If a character has a high passive insight, then is the DM supposed to reveal all the plot secrets, and say things like: "Edgar the merchant comes to you and tells you that his daughter has been kidnapped, but Bob, your character has a high passive insight, so you think he might be lying to you." With a passive insight, it creates a situation where some players just know all the easy secrets and answers automatically. It prevents the ability of the DM to create mysteries, or problems that the PCs have to solve or work through if one character always has a good hunch about what's going on. And when "Bob" gets told that his character has a hunch about something, all the other players know that's correct information, which makes it difficult to play their characters as though they came to other conclusions.
Sometimes a PC's hunch is just way off, and I prefer to have them roll an insight checks whenever they want, where they might roll low. This is also one of the few rolls I will make behind the screen, so that when one or multiple characters ask to know if an NPC is trustworthy or lying, different characters may get told different things depending on their secret roll, and they simply must role-play their character based on the hunch they each get, because they don't really know how the roll went. It causes the group to perhaps rely on the one character who is very wise (has a high insight modifier) and is often able to suss out a situation correctly. But sometimes even that player gets things wrong.
So those are my reasons. Any other opinions on this?
) but then another (say the rogue) says "I'm keeping an eye out for traps" - passive perception. But as they've already declared that they're being stealthy how can they do both (in game mechanics) but in real-life that seems perfectly reasonable.
