789. Since the promulgation of the Gospel (see 342, 354), it is also necessary as a means that one believe explicitly in the mysteries of the Trinity and Incarnation. For he who does not accept these, does not accept the Gospel, whereas Christ says: “Go ye into the whole world, and preach the Gospel to every creature. He that believeth not shall be condemned” (Mark, xvi. 15, 16). (a) Theoretically, this opinion seems more probable than the opposite opinion; but chiefly on account of the difficulty about negative infidels, which is discussed in dogmatic treatises on Predestination and Grace, many theologians either reject it (e.g., those who say that belief in the two great Christian mysteries is necessary only as a precept, or that implicit faith suffices), or modify it (e.g., those who say that belief in these two mysteries is not necessary as a means for justification, but only for glorification, and those who say that regularly such faith is a necessary means, but that an exception is allowed for invincible ignorance, or for the insufficient promulgation of the Gospel in many regions). (b) Practically, this opinion is safer, and hence all theologians, even Probabilists, hold that one must act as if it were true and certain, whenever it is possible to give instruction on the Trinity and Incarnation. 790. Knowledge about the mysteries of faith is either substantial (by which one knows the essentials of a mystery) or scientific (by which one knows also its circumstances and details, and is able to give a more profound explanation of it). Scientific knowledge is required, on account of their office, in those who are bound to teach the faith, but substantial knowledge suffices for salvation. Hence, for an adult to be saved, it suffices that he have the following kind of knowledge about the four great mysteries: (a) There is a God who has spoken to us, promising freely that He will take us to Himself as our reward. It is not necessary that one understand such theological concepts as the essence of deity, the definition of supernaturality, the formal and material objects of beatitude, etc.; for many persons are incapable of understanding them. (b) This God, who will be our reward, is one, but there are three divine Persons--the Father, the Son and the Holy Ghost, really distinct and equal. It is not necessary that one understand the distinction between nature and person, nor subtle questions about the processions and properties. (c) God provides for us, giving us the helps we need, and also, if we serve Him, the reward He has promised. It is not necessary that one understand the theology of providence, grace, and merit. (d) Jesus Christ, who is God the Son, became man, suffered and died for us, thus saving us from sin and winning back for us the right to heaven. It is not necessary that one understand scientifically that in Christ there are two natures united hypostatically in the one Person of the Word.