(b) In negative doubt of law regarding the validity of a past act, use the principle _that what was done is to be held as rightly done_. Example: He who has no reasons, or only trifling ones, for thinking that a Sacrament was not administered validly or received validly, should decide for validity. (c) In negative doubts of fact, use the principles that one should judge according to what usually happens, or that facts must not be taken for granted but must be established, or that presumption favors that which has possession. Examples: If there is no good reason to think that a conscientious person gave consent to a temptation, one may decide for the negative, since that would usually be true. If there is no good reason to think that one has made a vow, one may decide for the negative, since the burden of proof is with the other side. If, in a question about fast and abstinence, it is uncertain whether or not a person has reached twenty-one years, or whether Friday has commenced, the presumption is for the negative, since liberty has been in possession; but if it is uncertain whether a person has reached the age of sixty or whether Friday has ended, the presumption is for the negative, since the law has been in possession. 715. Having discussed the cases to which Probabilism is not extended, we pass on to the cases to which it is applied. Probabilism is used in any and every case where speculative certainty as to what is lawful or unlawful is not had, but where there is only speculative probability against an opposite probability. (a) Probabilism is used not only in probability of law, but also in probability of fact that can be reduced to probability of law, as was explained above (see 712). (b) Probabilism is used in probability of law, whether or not the question be about the existence or the cessation of the law. There is probability against existence of law, when one has good reason to think that a law was not made or not promulgated, or that the time when it goes into force has not arrived, or that it does not apply to certain persons or circumstances, etc.; there is probability for cessation of law, when it is certain that a law did exist, but one has good reason to think that it ceased or was abrogated, that one is excused or dispensed from it. (c) Probabilism is used in probability of law, whether the law in question be natural, divine or human--that is, in every case of law where invincible ignorance is possible (see 319 sqq., 356).