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 legal question arises about an action. If uncertainty exists regarding the validity of a valid action, acting solely on probability isn't sufficient unless that probability is so strong as to compel the Church to provide what's needed for the act's validity. These systems don't allow for actions based solely on probability when the validity of sacraments is in question, except in cases of necessity.