The Christian church must clearly refute the papal antichrist as well as other false teachers, and not follow their heresies or their example.
The Biblical teaching concerning the antichrist also belongs to doctrine of the Ministerial Office, namely the refutation of false teachers and refutation of those, who misuse the correct Pastoral Office. The devil is always striving by all means to make futile God's good intention to save mankind and therefore raises against sayers and false teachers to ruin the work which Christ by means of his pure Word is doing e.g. through the Pastoral Ministry. So is the battle between the right Gospel and false gospels continuous.
The antichrist rules in the church. He is not "man of God", but "man of lawlessness" and is an oponent of Christ, 2 Thess. 2:3-4. The main feature of opposition to Christ touches Christ's chief work, the work of redemption, and its significance. The basic tenet of the antichrist is to oppose the doctrine of justification based on Christ's once-and-for-all work of redemption, and to teach falsely concerning it. His basic identifying mark is his false doctrine of justification. Preaching the Law and keeping it in the forefront does not make the antichrist and his activity Christian. 2 Thess. chapter 2 lists the identifying marks of the antichrist: A falling away and lawlessness, exalts himself above the government or everything that is called God, "showing himself that he is God", for example by claiming to be above all criticism and the Biblical norm, prescribes works for the saints in heaven, invents new doctrines (for example the infallibility of the pope, the immaculate conception of Mary and her ascension into heaven), prescribes fasts, indulgences, counterfeit miracles, claims to be Christ's vicar on earth, etc. When we bear in mind that opposition to Christ manifests itself by opposing the truth that Christ atoned for the sins of the world once-and-for-all and finally, and that this completed justification is possessed solely by faith without the deeds of the Law, it is not difficult to understand that the pope with his systems is that man of lawlessness, the antichrist. Spanheim has correctly said: The Pope puts aside the prophetic office of Christ through his traditions, the kingly office through the power he has taken for himself, the pontifical office through those offerings he makes his priests do" (cited by Hoenecke IV,222).
Although the pope church is teaching Law strongly and without flattering people, it has many kind of false opinions also in understanding of Law and in its applications.
2 Thess. 2:8 says that the antichrist will be active for a long time, longer than a lifetime of one person. Christ is killing him first at his advent. The antichrist is therefore not just one person in the very end of this world, but a phenomenon in a long course of time. It is the papal church led by the pope. We may with our Confessions say that the marks of the antichrist fall entirely together with the papal church.
According to the Bible the coming of the antichrist "is according to the working of Satan with all power and signs and lying wonders, and with all deceit of unrighteousness for them that perish" (2 Thess. 2:9,10). "The mystery of lawlessness" (2 Thess. 2:7) was there already during the apostolic time, but it could not come out as the power of the antichrist; first prevailing restraints had to be removed. The papal system was built on the ruins of the Roman Empire and was not possible before the Roman Empire had fallen. The secular powers (Obrigkeit) – in spite of the fact that there were so many unjust and immoral rulers and persecutors of Christian – were, however, the outward order (Ordnung) set by God, which prevented the antichrist from coming into power. During the time of Roman emperors Christians were persecuted from outside, when the antichrist is in power persecution comes from inside. The antichrist puts his own doctrine to replace Christ's doctrine and his own men into the Office, which should teach the pure Gospel.
The coming of the antichrist happens "for them that perish", "because they received not the love of the truth, that they might be saved". (2 Thess. 2:10). The appearace of the antichrist is very harmful matter to souls.
According to the Bible there are also many other antichrists. "Little children, it is the last hour: and as ye heard that antichrist cometh, even now have there arisen many antichrists; whereby we know that it is the last hour... Who is the liar but he that denieth that Jesus is the Christ? This is the antichrist, even he that denieth the Father and the Son." (1 John 2:18,22.) "And every spirit that confesseth not Jesus is not of God: and this is the spirit of the antichrist, whereof ye have heard that it cometh; and now it is in the world already" (1 Joh. 4:3). "For many deceivers are gone forth into the world, even they that confess not that Jesus Christ cometh in the flesh. This is the deceiver and the antichrist" (2 Joh. 7).
Antichristian spirit is not to be feared only as it appears in the papal church , but it is to be rejected in all its forms. The antichristian spirit is influencing everywhere there, where the Scripture is denied as the only source and norm of doctrine, where to those things which influence our salvation is added something done by ourselves, i.e. to the redemptive work of Christ and to the work of Holy Spirit through the means of Grace. We have to reject synergism, historico-critical method, enthusiasm, believes in tradition, etc. All those trends coming from man's heart prepare, in a way or another, sympathy to the papal church. They all have a joint denominator, a joint origin – man. Under that spirit one cannot see the destructive influence of wrong doctrine on justification.
All antichristian heresies and false practices must be unequivocally refuted, and we must beware that we do not follow the example of the antichrist and other false teachers.
The antichrist is in Christian church, but it does not mean the antichrist himself with his heresies would be Christian. There are today over one million people, and if we think of baptized small children, the majority of those, who are true Christians in this world must belong to it. It is complexio oppositorum, also with many correct things; otherwise the antichrist would not be in church. However, the primacy of the pope, his position as the leaser of the Christianity and as the successor of Peter cannot be questions in the papal church. Accepting the primacy of the pope means already in itself denying the true doctrine on justification.
Regardless of how the words in the tiara "Vicarius Filii Dei" are to be understood, the pope demanding to acknowledge his primacy is putting himself on the place of Christ. Regardless of the numerical value 666 of the letters in the tiara we have to conclude that the pope is not representing with his doctrine the divine perfectness, but is representing human imperfection, very detrimental for salvation of men. In the Scripture the number of divine perfectness is seven. The number of the beast 666 is the number of man.
The papal church teaches a threefold synergism in doctrines of redemption, conversion and revelation. In all these three areas the papal church takes something away from divine perfectness and adds human to divine. So the papal church remains in 666 and does not reach 777. I think that God through his providence has led the things so that the number of man can be read also in the tiara, that God's children could avoid its doctrine on salvation by human deeds.
Number 666 can be found in addition to tiara also in a Hebrew word (רומיית), which means 'exaltations' and in a Greek word λατεινος, to which already Irenaeus referred. According to the Bible the number can be counted by those who have understanding (Rev. 13:18).