Sacred Haven of Debauchery

one does not contradict the other. if you don't have it, you don't need it to burn.

It does contradict. The task: wipe your hands on your pants. Let's go the other way around, if your pants are on fire, as you suggest. Pants on fire -> you can't wipe your hands, because the tar will ignite when heated, which means you won't be able to wipe it off, as the burning tar will completely stick to your hand. Therefore, the conclusion: if your pants are on fire, the task becomes impossible. If, however, your pants are not on fire -> the tar does not ignite -> you can easily wipe your hands on your pants -> the task is completed.
And don't lie, or I'll excommunicate you from the Haven.