Unshaven and anonymous
On John 16:3 ("And they will do this because they have not known the Father nor Me.")
The true knowledge of God and of Christ has often been defined. It is not an idle, empty thought or dream, as reason is able to think of God and Christ on the basis of hearsay, and as it pictures Him and acts toward Him according to such thoughts of its own. No, it is the true and living faith, which understands the words of the Gospel and, in accordance with those words, knows Him and the Father's will and heart. It knows that the Father sent Christ, His Son, to deliver the world from sin, God's wrath, and eternal death through His blood and death. It tells man that Christ accomplished all this, gained forgiveness of sin and eternal life, and surely bestows this on all who believe in Him. Thus the knowledge of God and of Christ are bound together and are one knowledge. As has been repeatedly said, the Father is known solely in Christ and will not and cannot be attained and met or worshipped and called upon apart from this Mediator.
Therefore all depends on this article about Christ, and he who has this article has everything. In order to be able to abide by it, the Christians must be engaged in the most strenuous warfare and must fight constantly. Therefore Christ and the apostles have good reason to insist on it everywhere. Although the other doctrines are also based on Scripture – for example, Christ's birth from a pure virgin – it does not stress them as much as it does this one. When St. Paul champions this doctrine of Christ's birth, he does not even call the mother by name; nor does he mention the honor of the virgin; he states simply (Gal. 4:4) "born of woman." But when he informs us that we receive grace and salvation, not by works and the Law but only through this Mediator, Christ, then he speaks exhaustively.
This is also the only doctrine that is constantly subjected to persecution by the devil and the world.... Where this doctrine is proclaimed, there the devil is mad and insane, and the world is aflame with anger and raging.
Throughout history we find that all heresy and error has arisen where this doctrine has disappeared, where people became smug, as though they knew it very well, and thus turned from it to something else and began to dispute about the Person of Christ, whether He was true God or a mere man. With such speculations and questions they opened the door to every evil. The one denied the divinity of Christ; the other, His humanity. Some denied the Person of the Holy Spirit; others, the virginity of Mary. But they all, as many as there were, also erred in this chief doctrine and misled others, For all other doctrines stand and fall with this one; it includes all the others; it is all-important. He who errs in the others certainly errs in this one too. Even if he holds to the others, still all is in vain if he does not have this one.
On the other hand, if one abides by this article diligently and earnestly, it has the grace to keep one from falling into heresy and from working against Christ or His Christendom. For the Holy Spirit is surely inherent in it, and through it illumines the heart and keeps it in the right and certain understanding, with the result that it can differentiate and judge all other doctrines clearly and definitely, and can resolutely preserve and defend them. This we see in the old fathers. When they retained this article of faith and based their doctrines on it, or derived them from it, they preserved purity of doctrine in every detail. But when they departed from it and no longer centered their arguments in it, they went astray and stumbled with a vengeance, as happened at times to the oldest, to Tertullian and Cyprian. And this is also basically the failing not only of the papists but of our schismatic spirits, who rant against Baptism and other doctrines. They have already surrendered this article of faith and have paid no attention to it. Instead, they have put forth other matters. In this way they have lost a proper comprehension of all doctrines, with the result that they cannot teach anything about them that is right and can no longer preserve any doctrine as unquestionable. This can be seen in their books. And now they lapse from one error into another, until they finally land themselves and others into perdition.
For where this knowledge of Christ has vanished, the sun has lost its brilliance, and there is nothing but darkness. Then one no longer understands anything aright and cannot ward off any error or heresy of the devil. And even if the Word concerning faith and Christ is retained – as it has remained in the papacy – the heart has no foundation for a single doctrine. (...)
On the other hand, where this sun shines and illumines the heart, there is found a true and certain understanding of all things. (...) Where this knowledge if gone, it has taken everything with it. Then you may accept and confess all the other doctrines, as the papists do; but there is no serious and true understanding. (...)
Behold, that is the reason why Christ impresses this doctrine so emphatically and so constantly on the minds of the apostles; that is why He commands them to teach it, and why He warns them against all offenses that would tend to tear them away from it. For He knows that if they cling to it as the fundamental and chief article of faith, they are in the lap of the Holy Spirit, who arms and protects them, so that they have strength enough to come off victorious against all offense and error, and to overcome everything that happens to them. For this knowledge does all these things. It affords us all wisdom; it gives us God with all His goods; it opens heaven; it shatters hell, the devil, and the world with all their wisdom and might, lies and murder.
For if they really knew God the Father and Christ, His Son, they themselves would have to join us in concluding from such knowledge: "We believe that we cannot be saved in any other way than through the one Mediator, Christ, who was sent by the Father to bear and to pay for the sins of the world, as is set forth incisively and powerfully in St. Paul's discussion and conclusion. For to know the Father means to know God's plan for us; it means to know the purpose for which He sent His Son; to redeem us from sin, since the Law could not help us (Rom. 8:2-3.)" (...)
...Christ says: "Through Me, not through yourselves or through any other name in heaven or on earth, you are to be saved."