We are accustomed to the claim that appropriate backing must be available if criticism is to be justifiable. For example, if someone criticises a film he must be prepared to cite the criteria he is using and to show how they are or are not satisfied by the film. Such processes of evaluation have frequently been investigated: what has been less thoroughly sexplored is the right to criticise itself. Certainly, questions of the appropriate backing for critical utterances have bearing on the right to criticise (as I shall show), for one way of denying that a person has that right is to deny that he can provide the appropriate backing for his criticism. But the question of his right is a wider one, since the attempt to criticise may be blocked before the question of backing can arise at all. It is therefore worthwhile to explore the right to criticise with a view to discovering in what circum-stances it is defeasible. I shall be concerned mainly with the moral right to criticise as investigation of the legal right would raise issues for specialists in the laws of libel and slander.