Falkus said:
You're also forgetting that traps usually don't require the participant to play an active role in his own destruction, by the very nature of a trap. A trap should be set off by stepping onto a hidden trigger, or a tripwire, or hooked to a door, not a lever that the target has to pull.
Every trap that has ever existed has required the target to play an active role in his own destruction. Even a bucket of water balanced on a door ajar requires the target to try to walk through the door. Are you seriously telling me that there are no trap triggers that involve opening doors, opening chests, etc?
If a trap requires you to step in a particular spot, you must step in that spot to set the trap off.
If a trap requires you to pull a tripwire, you must move in the area where the tripwire is located.
If a trap is hooked to a door, you must try to open the door.
If a trap requires you to pull a lever, you must pull the lever.
All traps, regardless of their actual mechanism, require some lure to make the being to be trapped enter the trap. A mousetrap is baited, and by eating the bait the mouse causes the trap to release. A sliding chute trap is hidden down a corridor, and by traversing the corridor a character causes the trap to spring open, sending him down to the garbage pit where the otyugh lives.
Smart trap-setters use a lure that will entice the desired target to engage the trap. Hence, you bait your mousetrap with cheese or peanut butter and not fluff from under your couch. A roach motel or fly strip offers a scent that roaches or flies are likely to investigate. A kobold puts an obvious "treasure" beyond the area with the spiked pit. In one dungeon, two identically dressed goblins wait, one to duck into a secret door around the corner, and one to duck around the corner when the party approaches, luring them into the spiked pit between the two locations.
Every trap everywhere. Mechanism and lure. Even when the trap is in an otherwise deserted hallway, traversing the hallway acts as a lure to a trap. Traps do not go out seeking adventurers. Traps do not wander the halls waiting to slide under people's feet. Traps are not creatures. If they were, they'd be monsters. Or hazards, like green slime and brown mold. Every trap that has ever existed has required the target to play an active role in his own destruction.
By its very nature, a lever implies that, by changing its position, you cause something to happen. This makes a lever very different from, say, a raised dias, a table, a torch, or a statue. All of those things might do something; it is a far more reasonable (and obvious) assumption that a lever or a switch will do something.
(It might not, of course. It could be a red herring. The mechanism could be broken. However, even if you see no obvious result, it is safe to assume that throwing the switch/lever has had some effect that you should, thereafter, keep your eye out for.)
In other words, a lever is automatically and (with very, very few exceptions) always a MECHANISM.
In the example room, there is a secret door. A secret door implies both a space beyond (although this may not be true; it may be a false secret door leading to a stone wall) and a means to open it (again, this implication may not be true; the secret door could be built in such a way that it has no regular means to open it, especially if it is intended as bait rather than as a door).
In the example room, we have a secret door with no means to open it, and a lever that does something that we do not know. So here we have two objects. One does something, the other needs the means to do something. The easiest solution to the problem is that the one object does the something for the other object. We do not think any further, throw the lever, and roll a saving throw.
In other words, the secret door is a LURE.
If you cannot put together MECHANISM + LURE = PROBABLY TRAP then
it is your own fault, not the fault of the DM.
Some might say that there's a million and one different possible reasons for a lever to be in a room with a secret door. They might claim that only a small percentage of the suspicious and paranoid would say "obvious trap." However, to say so means you simply do not understand the nature of traps, in real life or the game. MECHANISM + LURE = TRAP.
You open the door. Beyond the door is a 30 x 30 room, empty except a big pile of gold coins in the middle of the floor. What do you do? Hmm. Can't see the mechanism, but that sure looks like a lure.
You see a big lever and find a secret door that you cannot find the way to open. Mechanism and lure. Hmm.
You are crawling along the kitchen floor when you find that someone has kindly left out a big piece of cheese for you. Hey, nothing suspicious here......
If one can say that the scenario in the original post wouldn't be unfair if it was an obvious trap, then let's see someone at least attempt to show where my reasoning falls down.
RC