An Imprimatur is an official eclaration from the hierarchy of the Roman Catholic Church that a literary or similar work is free from error in matters of Roman Catholic doctrine and morals, and hence acceptable reading for faithful Roman Catholics. Ordinarily an imprimatur is granted by the bishop of a diocese (after a declaration of nihil obstat has been granted by a theologian in regard to the work). On rare occasions, a bishop's imprimatur may be overruled by higher authorities within the Catholic Church; this happened twice in 1984 and again in 1998.