791. Since Baptism is fruitless without due faith in the recipient, it is not lawful as a rule to baptize those who lack substantial knowledge of the four mysteries just mentioned. (a) Outside of danger of death, it is never lawful to baptize a person, adult in mind, who is in substantial ignorance of any of these four mysteries. Such a person must first receive instruction. (b) In danger of death, when instruction cannot be given, an adult in substantial ignorance about the Trinity and the Incarnation may be baptized conditionally; for it is probable that explicit knowledge of those two mysteries is not a necessity of means (see 789; Canon 752, Sec.2). 792. Since absolution is invalid if the person absolved is incapable of receiving grace, and since acts of faith in the four chief mysteries are an essential means to justification in adults, absolution given to one who is in substantial ignorance about one of the four mysteries above mentioned is certainly or probably invalid, as the case may be. Absolution certainly invalid is never lawful, but absolution probably valid may in certain cases be regarded as lawful before administration, and as valid after administration. Hence, the following cases must be distinguished: (a) Outside of danger of death, it is not lawful to absolve one who is in substantial ignorance about any of those four mysteries. Such a person should be sent away for further instruction, or given a brief instruction then and there, if there is time. (b) In danger of death, when instruction cannot be given, an adult in substantial ignorance about the Trinity and Incarnation may be absolved conditionally, for the reason given in the similar case of Baptism. (c) After the fact, absolution given to one who was in substantial ignorance of the Trinity and Incarnation, may be regarded as valid, since the opinion that explicit knowledge of these mysteries is not a necessary means, is at least probable. Hence, according to the principles of Probabilism a penitent who made confessions While ignorant of those two mysteries is not obliged to repeat his confessions, since he has probably satisfied his obligation. 793. In the following cases (which would be rare, it seems) Baptism or absolution cannot be administered, even to the dying who are unable to receive instruction: (a) when it is certain that the dying person is substantially ignorant about the existence of God, the Author of grace and glory; (b) when it is certain that the dying person is substantially ignorant of the Trinity and Incarnation through his own fault, and is unwilling to hear about them. 794. Practical rules for granting the Sacraments in case of doubt or urgency to those who seem to be indisposed on account of substantial ignorance are the following: (a) In danger of death, when instruction is out of the question, if there is doubt about his ignorance, the dying person should be given the benefit of the doubt.