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You can either do Perception or Investigation checks in order for your character to search for something.

My question is : can you search for the absence of something?

If you can, then what are the implications of such a search? For example, provided that the object (that you're searching the absence of) is actually not there, and that you fail the check, should you (and only you) then THINK you see evidence of the object possibly being there even if it's not ?

Example: You may search for traps in a trapped area, fail the check, then think there are no traps. Now, let's reverse the situation : you search for the path being clear (the absence of traps) while the path is empty of any traps, but you fail the check. Should your DM then inform you that there might be traps, as part of the uncertainty brought by your failure ?

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closed as unclear what you're asking by Novak, Tim Grant, Oblivious Sage, Miniman, Gael L Jul 19 '17 at 0:49

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ I guess for me you haven't yet shown an example where it would be more beneficial to search for the absence than for the object itself. \$\endgroup\$ – David K Jul 18 '17 at 19:32
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    \$\begingroup\$ @DavidK You make a valid point. This is a temporary message (not for discussion purpose) to say that I intend to find such a beneficial example. \$\endgroup\$ – Gael L Jul 18 '17 at 19:41
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    \$\begingroup\$ Is this purely hypothetical or does some real-gaming situation hinge on this? \$\endgroup\$ – Novak Jul 18 '17 at 21:30
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    \$\begingroup\$ Vote To Close: There's no actual problem, here. \$\endgroup\$ – Novak Jul 18 '17 at 22:31
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    \$\begingroup\$ In fact, the premise "you can either do Perception or Investigation checks in order for your character to search for something" isn't correct. You don't do any checks in order for your character to do X. Instead, you say "I do X" to your DM, and then your DM might ask you "make a Y check". \$\endgroup\$ – enkryptor Jul 19 '17 at 10:05
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The situation you are describing is "search for traps". You might hope to discover that the trap is not present, but in real life, you would do the same things to search for a trap that you thought you would find and to search for one that you'd hope to not find. Similarly, in game, you use the same mechanic, with the same failure states (ie, you won't find the trap regardless of roll if the trap is not there, and you won't find the cat if your roll fails, regardless of whether or not it's there).

In the case of "search for a clear path through the traps", again, what you're actually looking for are signs of the traps themselves. If you fail, then it's likely because you missed a trap that was there, and you will "find" a path that has traps in it.

If you were able to perceive the signs of passage of the natives of the place, you might search for paths that were frequently used, but that requires that you be able to spot those indicators. The difficulty is going to be higher. Also, it wont' tell you about what traps are there - merely that the natives of the place use a certain path. If they're all particularly short goblins wearing cloth or leather, there's still a very real possibility that your paladin in platemail will set off something weight-dependent or get hit by something that would pass harmlessly above their heads. Likewise, they might be temporarily disabling along the way and re-enabling once past.

Other than that, though, when we're searching for "a safe path", what we really mean is a pathway that doesn't have traps or other dangers... which means we're actually searching for the traps or other dangers.

Of course, this is 5th ed, which actively welcomes and encourages houserules on things like this. If the DM wants to rule that a particularly bad perception failure in an empty room makes you think you see signs of a trap that isn't there, that's up to them. It seems like the sort of thing that could be entertaining if played right. I'd keep it rare, though. One or two false positives in trapfinding could work if done well, but having a great many seems likely to just slow things down with minimal payoff.

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  • \$\begingroup\$ The example has been changed. You may update your answer accordingly. \$\endgroup\$ – Gael L Jul 18 '17 at 16:40
  • \$\begingroup\$ @GaelL - have done so. \$\endgroup\$ – Ben Barden Jul 18 '17 at 21:16
  • \$\begingroup\$ Alrighty. But then, if you search for traps in an area where there are none, should a very bad failure give you the false information that there might be traps ? \$\endgroup\$ – Gael L Jul 18 '17 at 21:20
  • \$\begingroup\$ I am not aware of any rules that would call for that specifically, but it does sound like an interesting and entertaining houserule. I'll add that. \$\endgroup\$ – Ben Barden Jul 18 '17 at 21:27
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You can search for the absence of something,if you know it's supposed to be there using the investigation skill. Perception rolls give back raw information: scent touch sound sight. Investigation rolls will give you back processed information, IE you've reasoned about it.

Basically, youre saying in this situation I've encountered this before, and this should be here. A failed check in this case will likely end in the assumption that all is well. Otherwise, passing the check will indicate the absence of what you're looking to not be there.

The prime example of this is when you check for Traps. The default assumption is that you're looking for there to not be Traps. IE, the way is clear.

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  • \$\begingroup\$ Is there a difference between failing a check to find traps, or failing a check to not find traps? The first you were looking for traps, failed your check, and didn't find a trap that is there. The second you were looking for a clear path, failed and the path isn't clear even though you think it is. I don't think this is the same as what the OP was meaning. Or I'm completely failing my check as well. \$\endgroup\$ – CGCampbell Jul 18 '17 at 16:18
  • \$\begingroup\$ @CGCampbell Well, in the case of a "search if path is clear" check, let's say the path is actually clear, but you fail the check, the resulting failure would then be for you to be either uncertain of the safety of the path, or certain that it is filled with traps (so in other words, a negative outcome to your party). \$\endgroup\$ – Gael L Jul 18 '17 at 16:22
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    \$\begingroup\$ There is. It's that uncertainty thing. As a DM I'm never required to give you accurate information when you fail a check. If you're looking for there not to be Traps and you fail, i'm going to tell you there's evidence that it might be trapped. On the flip side, if you look for Traps and fail, i'm not going to tell you there's Traps, even if there are. \$\endgroup\$ – Adam Wells Jul 18 '17 at 16:24
  • \$\begingroup\$ The question's example has been changed for the clear path situation. \$\endgroup\$ – Gael L Jul 18 '17 at 16:41
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    \$\begingroup\$ “The prime example of this is when you check for Traps. The default assumption is that you're looking for there to not be Traps. IE, the way is clear.” doesn't seem accurate. If accurate, it would mean a successful roll finds no traps… and a failed roll also finds no traps. I see what you're trying to say, but I don't think it's actually working. When you search for traps, you're not trying to find absence, you're searching for presence of traps. \$\endgroup\$ – SevenSidedDie Jul 19 '17 at 16:30
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A good GM should always balance enforcing the rules with giving players the freedom to improvise. If the rules aren't fairly applied, then victory (or defeat) is meaningless, but if the players aren't allowed to use their imagination then we might as well just play video games.

Therefore, when we compare "I search the room for traps" and "I'm suspicious of this vile sorcerer's treachery - something's not right about this room. What's missing?" we see that they both are the same, mechanically, but one of them paints a much more interesting picture of the scene. A good GM should embrace that, rolling the check and describing what the character's suspicions reveal, building on the description. "You notice that unlike the last few rooms, there is no dust under the large worktables - the sorcerer's gnomish henchmen has been working in here."

The spirit of fair play says that we must reward characters who have invested in the skills, as well as characters who roll well. Logically, that means we have to punish poor rolls and unskilled characters to a degree. However, nowhere is it written that a failure has to be boring. A studious cleric who searches a room might miss a pit trap, but notice an antique manuscript is a forgery; A warrior might spot that the damaged windowsill once had sturdy bars ripped clean away. None of these details directly help the party pass the skill check and avoid the trap, but they build a more interesting world and reward the choices that the players have made.

In conclusion, reversing the wording of your question can make your investigation more entertaining, but it shouldn't necessarily make it more successful. (Then again, the gods often smile on entertaining characters.)

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A failed check doesn't neccessarily entail the opposite of a passed check. If a player searches for traps and rolls low, they don't find anything, regardless of the presence of traps. A low roll when searching for information should generally yield no information, or information of little obvious relevance.

In the case of "I search for not traps" I would inform the player that they are being a semantic munchkin, and enemies will start attacking "not the player with the highest AC."

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This question could have a lot of answers. It would seem illogical to fail such a check and believe it's there. For instance, I'm searching for an assassins signature, and you fail, it wouldn't make sense for you to believe you saw such a thing. It would be more logical for the character that failed to be uncertain about the assassins signature being present.

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  • \$\begingroup\$ So, in other words, you can do such a check, but failure only brings uncertainty, not actually seeing something that isn't there. Makes sense. \$\endgroup\$ – Gael L Jul 18 '17 at 16:12
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    \$\begingroup\$ Indeed, I think so. \$\endgroup\$ – Bigbo Biggins Jul 18 '17 at 16:14
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You can never prove a negative beyond a shadow of a doubt. As some of the other answers have stated, either the trap is there or it isn't. You can be certain that there is a trap if you find the trap. But you can't be certain that there isn't a trap if you fail to find one, because there can always be some detail that you overlooked. In fact, you can find a trap and still not find the second trap just a few feet beyond the first. @Bigbo Biggins hit it right when he talks about certainty, because essentially that's what you're rolling for. If you roll high, you searched more thoroughly and so you can be more certain that the next room/stretch of road isn't brimming with traps.

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Let me answer your question with a question. Suppose that I'm trying to hit an orc with my sword. Can I aim for "not that orc"? If I miss, does that mean I have struck the orc? Can I close my eyes when swinging, to give myself disadvantage on the roll and make it more likely that I'll miss and strike the orc?

Here's the answer to this question: no. That's crazy talk. Stop looking for weird rules-lawyery loopholes. If I try this, my DM should glare at me and tell me to roll to hit the orc, against the orc's normal AC.

The answer to your question is pretty similar.

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  • \$\begingroup\$ Your orc situation implies more than 2 possibilities (hit there, hit there, hit there). My situation is a Boolean ("you find" Vs "you do not find"). \$\endgroup\$ – Gael L Jul 18 '17 at 20:10

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