Most professional comedians have had the experience of failure to raise a laugh. Most of us have probably, at one time or another, told a joke that has utterly failed. In that sense, we can say that humour is a fragile thing. Of course, within our own culture, we can point to circumstances which reduce the chances of failure: the comedian who has already had a warmup man at work on the audience; telling a joke to friends where there has already been a lot of laughter (and maybe some drinking), for example. In tribal cultures we could point to the role of customary relationships in fixing a framework where joking will succeed; in medieval Europe the fact of customary roles and calendrical occasions such as the Feast of Fools would no doubt act as a similar form of insurance. These caveats about limited circumstances notwithstanding, the central point holds: jokes and other humorous attempts operate within a framework where they may not be received as such. And if they are not received as such, it is very unclear whether they are in fact humour: as Douglas says, a joke must be permitted as well as intended in order to accede to the status of joke.