The omission of the entire office of a day, the seven canonical hours, is held by some theologians to carry the guilt of seven mortal sins. Because, there is a different precept for each hour and the omission of each hour violates a precept. The Salamenticenses think this opinion probable. The more common and the more correct opinion is that by such omission only one sin is committed. And the theologians who hold this opinion say that the recitation of the canonical hours is imposed under one precept only, and hence there is only one obligation embracing the seven hours. This is the opinion of St. Alphonsus (n. 148) who quotes several authors (including Lessius, Sanchez and St. Antoninus) in support. If a person in Holy Orders omit several hours with a retractation, or a moral interruption in his sinful intentions, he may commit several mortal sins, because all the omissions, which in themselves are grave matter, may become independent of each other by the interruption and renewal of the intention (St. Alphonsus, n. 148). What must a person do who has a doubt that he has omitted something in his recitation of the office? Is he bound to make assurance doubly sure by reciting the part of which he doubts? If the doubt be a positive doubt, that is, if he have good reason to believe that he has recited it, he is not bound to anything further regarding the part in question. For instance, if a priest remembers having started the recitation of a lesson, and in a short time finds himself at the end of it, and cannot be sure if he have recited it, the presumption is in favour of the priest and of the recitation, because it is his custom to recite completely whatever part he commences. He has, thus, moral certainty that he has satisfied the precept, and it is not necessary to repeat it; if the necessity for repetition be admitted in such a case, a fruitful source of scruples is opened up. On the other hand, if the doubt be negative--that is to say, if a person has no reasonable motive for believing that he has recited the full office or the full hour, he is bound to recite the part omitted, because in such a doubt, the precept of recitation is, as the theologians say, "in possession." (St. Alphonsus, n. 150). It is not allowed to change anything nor to add anything to the daily office without permission. The Sacred Congregation of Rites (10 June, 1690, n. 3222) replied to a query, that in saints' offices nothing is to be added and nothing is to be changed, and this reply applies to all sorts of offices, old and new. THE ORDER TO BE OBSERVED IN RECITING THE DIVINE OFFICE.