Passive Perception: a Good Place To Start

Passive Perception works on a very simple premise: add your WIS modifier, and proficiency bonus if you have it, to 10. When you’re moving around, just paying normal attention to things, that’s the level at which you’re aware of things. If there’s something to be noticed, and the DC is below your Passive Perception, the DM just tells you that you see it there. No rolls needed. If you want to look at a particular thing specifically, then you might make a Wisdom(Perception) check by rolling a d20 and adding your modifiers.

If this sounds familiar, that’s because we used to call it “taking 10”. The difference is just that you are constantly taking 10 on your Wisdom(Perception) checks, all the time, everywhere, without ever having to bring it up. You just get information funneled right through your imaginary senses into your imaginary brain from the DM.

Because that’s how perception works in the real world. You see things, and the better you are at spotting things, the more things you see. If you want to take a really close look at something, that’s taking an action above and beyond just being aware of your surroundings. It makes sense. So much sense that I wonder why we aren’t using it for more things.

Knowledge-Based Checks

First off, let’s define what “knowledge-based” means in terms of skills and skill checks. If a skill consists of knowing about a particular topic or field of study, then that’s knowledge-based. Most, but not all, of these are tied to your Intelligence modifier; some are tied to Wisdom instead. But all of them have to do with your character having some specialized education or information on a particular topic:

The important thing to note here is that these skills represent knowledge and know-how that the character has about those topics. This is entirely different from the knowledge that the player has about those topics. And this is an extremely important distinction.

Surprise: Players Aren’t Characters

It seems really obvious, but a lot of DM’s can’t get their heads around this distinction. And, not making this distinction correctly frustrates players, and it damages games, and it gets characters killed. If you’re a DM who worries a lot about meta-gaming, by which you mean players should be drawn and quartered if they have the temerity to open the Monster Manual and learn some things from it, then not making this distinction is an especially serious problem for you. So, let’s have an example:

Now, if someone could explain to me why we expect Beth to know anything whatsoever about the plants and animals on the Sword Coast, or how to bandage arrow wounds, I would be much obliged. And shocked, as well, because Beth doesn’t know how to be a druid anymore than Alissandra can do your taxes. Please note: I didn’t say that Beth can’t roleplay a druid, or that she doesn’t know how the druid class ought to be used in a D&D game. I said that she isn’t really a druid. Because she isn’t.

Holding Back Knowledge

What it comes down to is that the only person sitting at that D&D table who can even be remotely expected to know everything about the fantasy world in which the characters are having their adventures is the DM. And the DM has the Monster Manual, and the Player’s Handbook, and the Dungeon Master’s Guide, and notes and books and campaign settings and every other reference right there to check out anything he or she might not know off the top of his or her head.

And that means, ultimately, that the players only know what the DM tells them. It’s right back to the basics: the RPG conversation means that the DM is the players’ window into the world. So, unless the players are looking things up in the reference books or on D&D Beyond or whatever (which is a thought that makes many DM’s cringe), they are clueless about the fantasy world in a way that their characters are not. And this creates a responsibility on the part of the DM, the designated informed person, to make sure that players learn things that their characters know.

Active Checks Are Not Enough

But that shouldn’t be a problem, because if a character has proficiency in a skill like Nature, they can always make a skill check to learn about a particular Nature-related topic. The problem is that this sort of thing keeps happening:

The first problem here is that Alissandra the Druid probably does know quite a bit about ochre jellies. If she has even modest stats and proficiency in the Nature skill, she should have about +3 or +4 to her Nature checks. That’s not a lot when you add it to a lousy d20 roll, but what if we calculated Passive Nature the way we do Passive Perception? Alissandra the Druid would have a 13 or 14 on her Passive Nature. Our generalization of DC values tells us that a DC of 13 or 14 is pretty moderate, so Alissandra probably has a moderate amount of knowledge about Nature topics. That exchange should go something like this instead:

What’s different? Well, for starters, the DM just came out and told Beth some useful information about the ochre jelly that Alissandra would know about with that Passive Nature of 14. In fact, the DM had that number written down behind the screen somewhere in order to know just how much information would be good to provide. Then, Beth wanted to see if Alissandra knew anything else useful, so the DM called for an active check to augment the passive score. The active check was better than the passive, so the DM gave some additional information on the jelly as a result.

In fact, the whole part of the exchange where Beth asks if there’s any more information to be had is only there to illustrate that active checks are a different thing than passive scores. Beth might have just taken the bit of information about the slashing damage and plowed ahead into the fight with a bludgeoning weapon.

Another thing that makes the second exchange better than the first is that using the Passive Nature score to give relevant information avoids the circumstance where Beth feels the need to roll a Nature check every time she meets a new animal. This would become tedious in the extreme, but Beth would really be foolish not to ask to make the rolls, because she might have learned something important if she had.

The same things apply for Arcana, and History, and Religion, and all the rest. Figure out the players’ passive scores for those skills, write them down, and use them to decide when to volunteer relevant information and how much to give out. I even keep Passive Medicine written down, and tell our cleric about types of wounds, and what kind of skeleton that is, and how long this corpse has probably been lying there.

The Proficiency Caveat

There is something that needs to be adjusted before additional passive checks can be used in your game. On all of those knowledge-based checks, a character must have proficiency in the skill in order to have a passive score. In fact, a character must have proficiency to make even an active check.

The reason for this is that when you have even four players at the table with one character each, there’s a high likelihood that, if you call for a d20 roll from each of them, at least one of them will get a pretty good result independent of any modifiers. This makes those knowledge-based checks meaningless, because one of the players is going to get a high enough roll to get whatever information they’re trying to get. And it might be the barbarian who rolls the high Arcana check, which makes no sense at all. Allowing everyone to roll for every check makes them meaningless, and it makes having proficiency in those knowledge-based skills pointless.

There are absolutely skill checks that should not require proficiency. Perception is the obvious one, because everyone has eyes in their head and can look around and see things. Investigation is another, as are pretty much all of the Charisma skill checks (with the possible exclusion of Performance, depending on your definition of what constitutes a performance). There are things that anyone can try, and then there are the things that require some level of expertise to even attempt.

Things That Shouldn’t Be Passive

It should go without saying that there are skill checks which should never be used as passive scores. I’m going to say it anyway, though. If a skill check is only used to evaluate the success or failure of a specific attempt to accomplish a definite task, then it should not ever be used passively.

For example, there can be no Passive Athletics, because we only use Athletics when a character is going to attempt a particular act of skillful bodily exertion. The same goes for Acrobatics, for the same reason. None of the conversation-related checks should ever be passive: when you try Deception, you are making an isolated attempt to trick or fool a particular person or group.

If you think that these sorts of checks would make sense as passives, I’m going to guess that it’s because “really strong and athletic people should have no trouble with unimpressive feats of strength” or something along those lines. If that’s your reasoning, I would suggest that you try adding the “take 10” rule back into your game: under the proper circumstances, a player can opt to accept a d20 result of 10 instead of actually rolling the d20.

A Brief Summary

First, there are skill checks that should require proficiency to even attempt, and the most obvious of these are the ones that require specialized knowledge. Requiring proficiency for these checks eliminates the high likelihood that some party member or other will roll high enough on the d20 to reveal almost any piece of information. It also makes the players’ selections for their characters to have proficiency in those knowledge-based skills a meaningful choice, because they might be the only one in the party who knows anything about a certain topic.

Second, there are many skill checks that can and should have passive scores in addition to being used actively. If a skill represents knowledge that a character would have but the player would lack, it should definitely be able to be used passively: the DM should volunteer a certain level of information based on the passive score, because Beth the Accountant doesn’t know about fantasy animals, but Alissandra the Druid does.

Finally, even if you decide to have the possibility of a passive score for a check, there should always be an opportunity for the player to ask a more specific question, and to make an active skill check to find out extra information. Passive Perception gives you information of a general nature when you enter an area, but you can choose to look more closely under the bed with an active Wisdom(Perception) check. That’s a good model, and it should be part of any passive-versus-active check relationship.

Remember, DM’s, you have to assume that the players only know what you tell them about the fantasy world that you are creating. Experienced players probably know some things already (like the trolls and fire bit that nobody ever seems to need to be told), but you can’t ever really know the extent of their knowledge, or even if it applies correctly to the world that you are interpreting to them. You are the players’ sole window into your world: hold up your end of the conversation and be a good window.