Any invention the publication or exploitation of which would be contrary to "ordre public" or morality is specifically excluded from patentability. The purpose of this is to exclude from protection inventions likely to induce riot or public disorder, or to lead to criminal or other generally offensive behaviour (see also II, 7.2). Obvious examples of subject-matter which should be excluded under this provision are letter-bombs and anti-personnel mines. In general, this provision is likely to be invoked only in rare and extreme cases. A fair test to apply is to consider whether it is probable that the public in general would regard the invention as so abhorrent that the grant of patent rights would be inconceivable. If it is clear that this is the case, objection should be raised under Art. 53(a); otherwise not. If difficult legal questions arise in this context, then refer to VI, 7.8.