These various moral systems come into play only when the question concerns the lawfulness of an action. If the uncertainty concerns the validity of an action which must certainly be valid, it is not enough to act on mere probability unless, indeed, this is of such a nature as to make the Church certainly supply what is needed for the validity of the act. Thus, apart from necessity, these systems do not allow one to act on mere probability when the validity of the sacraments is in question.
These moral systems are invoked only when a question arises about the legality of an action. If uncertainty pertains to the validity of an action that must certainly be valid, acting solely on probability is insufficient unless such probability is so strong as to make the Church provide what's needed for the act's validity. Consequently, these systems do not permit one to act based solely on probability when the validity of sacraments is in question, apart from necessity.