Passive checks or active checks when looking for monsters or hidden objects?

Question

The basic rules 0.1 state on p61:

When your character searches for a hidden object such as a secret door or a trap, the DM typically asks you to make a Wisdom (Perception) check. Such a check can be used to find hidden details or other information and clues that you might otherwise overlook.

But they also state on p59:

Passive checks [...] 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.

Which seems like a contradiction: "you use a passive check for secret doors" and "you roll a check to find secret doors".

1. If a PC isn't actively looking for a secret door or monsters does it mean they don't get a chance to spotting them at all? (eg: interrupt an ambush)
2. When a PC is actively looking for hidden objects or secret doors are they supposed to roll or not?

I like the version where they don't roll because that way they have no idea if they flunked the check or not. On the other hand I like the version where you roll a die because it adds randomness to the game. In any case, before house ruling this I would like to know if anyone knows the intent of the rules as they are now.

Answer 1

Passive skills (especially perception, but anything really), are representative of a sort of "always on" ability. So, for instance, if you're walking in a forest and there is a goblin ambush, you see them if your passive perception beats their stealth score. However, if you're specifically looking for ambushes, you'll roll it actively.

So in the secret doors case, when you walk into a room, if your passive perception is high enough to spot the secret door, you notice it. If you're specifically looking for a secret door, then you roll an active check to try to notice (naturally, if you roll less than 10, you don't learn anything new).

Generally, the only time to roll an active perception check is if you are looking for something that your passive perception did not pick up. Naturally, in the course of play this happens fairly regularly. But the passive skills are designed to reflect a characters natural competence and should be used when they are sufficient, or there is no particular rush.