[pcrh]

>its goal should be to bring a novel contribution to the state of the art in the field

I would qualify that statement by saying that the goal of a PhD should be to demonstrate the ability to bring novel contributions, etc.

It is impossible to predict the outcome of a truly innovative project, which ideally the PhD candidate is engaged in, so the failure of any such project shouldn't be a reason to deny graduation.

The candidate should be judged instead on their ability to do research correctly, i.e. with the goal of discovering facts, however inconvenient they may turn out to be, rather than be coerced into churning out yet more useless publications with overblown claims.