There's a Reaper in the Basement

Using an example from Ultima Underworld II as a starting point, Jay Barnson muses on alternative objective solutions in RPGs on his blog. Specifically, he talks about those times where the developers encourage players to avoid combat but fail for various reasons:

Lord British has a very powerful Reaper in his basement in Ultima Underworld II: Labyrinth of Souls. This is a problem. But maybe not in the way you expect.

It's extremely hard to defeat, but not impossible. Therein lies the rub. If it was (level appropriate,) it would be just another combat encounter. If it was clearly impossible, players would have known better than to try and take it on, and would have quickly pursued other measures to get the treasure it guards.

But instead, through the miracle of saving and reloading, that desperately improbable fight becomes merely. unfair and frustrating. That slim chance becomes a matter of patience.

...

But no, the whole point was to encourage you to try a non-combat solution. To encourage you to be clever. Eventually, Looking Glass got it right, with the Thief series, but they did it by constraining the environment and the tools. Even when you were doing exactly what the developers expected you to do, you felt like you were cheating. But in a more open-ended RPG, this is still a problem.

...

Ultimately, the player has to be made aware of three things:

#1 That a direct confrontation is undesirable.

#2 That alternatives exist

#3 That choosing alternatives will not be punished