But there is no union between the Prince of light and the prince of darkness, and there can be no union between their followers

But there is no union between the Prince of light and the prince of darkness, and there can be no union between their followers. When Christians consented to unite with those who were but half converted from paganism, they entered upon a path which led further and further from the truth. Satan exulted that he had succeeded in deceiving so large a number of the followers of Christ. He then brought his power to bear more fully upon these, and inspired them to persecute those who remained true to God. None understood so well how to oppose the true Christian faith as did those who had once been its defenders; and these apostate Christians, uniting with their half-pagan companions, directed their warfare against the most essential features of the doctrines of Christ. GC 45.1

But as persecution ceased, and Christianity entered the courts and palaces of kings, she laid aside the humble simplicity of Christ and His apostles for the pomp and pride of pagan priests and rulers; and in place of the requirements of God, she substituted human theories and traditions. The nominal conversion of Constantine,  in the early part of the fourth century, caused great rejoicing; and the world, cloaked with a form of righteousness, walked into the church. Now the work of corruption rapidly progressed. Paganism, while appearing to be vanquished, became the conqueror. Her spirit controlled the church. Her doctrines, ceremonies, and superstitions were incorporated into the faith and worship of the professed followers of Christ.

This compromise between paganism and Christianity resulted in the development of “the man of sin” foretold in prophecy as opposing and exalting himself above God. That gigantic system of false religion is a masterpiece of Satan’s power—a monument of his efforts to seat himself upon the throne to rule the earth according to his will.

Satan once endeavored to form a compromise with Christ. He came to the Son of God in the wilderness of temptation, and showing Him all the kingdoms of the world and the glory of them, offered to give all into His hands if He would but acknowledge the supremacy of the prince of darkness. Christ rebuked the presumptuous tempter and forced him to depart. But Satan meets with greater success in presenting the same temptations to man. To secure worldly gains and honors, the church was led to seek the favor and support of the great men of earth; and having thus rejected Christ, she was induced to yield allegiance to the representative of Satan—the bishop of Rome. GC 49.2 – GC 50.2

Romanists have persisted in bringing against Protestants the charge of heresy and willful separation from the true church. But these accusations apply rather to themselves. They are the ones who laid down the banner of Christ and departed from “the faith which was once delivered unto the saints.” Jude 3. GC 51.2

The spirit of concession to paganism opened the way for a still further disregard of Heaven’s authority. Satan, working through unconsecrated leaders of the church, tampered with the fourth commandment also, and essayed to set aside the ancient Sabbath, the day which God had blessed and sanctified (Genesis 2:2, 3), and in its stead to exalt the festival observed by the heathen as “the venerable day of the sun.” This change was not at first attempted openly. In the first centuries the true Sabbath had been kept by all Christians. They were jealous for the honor of God, and, believing that His law is immutable, they zealously guarded the sacredness of its precepts. But with great subtlety Satan worked through his agents to bring about his object. That the attention of the people might be called to the Sunday, it was made a festival in honor of the resurrection of Christ. Religious services were held upon it; yet it was regarded as a day of recreation, the Sabbath being still sacredly observed. GC 52.1

Protestants now urge that the resurrection of Christ on Sunday made it the Christian Sabbath. But Scripture evidence is lacking. No such honor was given to the day by Christ or His apostles. The observance of Sunday as a Christian institution had its origin in that “mystery of lawlessness” (2 Thessalonians 2:7, R.V.) which, even in Paul’s day, had begun its work. Where and when did the Lord adopt this child of the papacy? What valid reason can be given for a change which the Scriptures do not sanction?

In the sixth century the papacy had become firmly established. Its seat of power was fixed in the imperial city, and the bishop of Rome was declared to be the head over the entire church. Paganism had given place to the papacy. The dragon had given to the beast “his power, and his seat, and great authority.” Revelation 13:2. And now began the 1260 years of papal oppression foretold in the prophecies of Daniel and the Revelation. Daniel 7:25; Revelation 13:5-7. (See Appendix.)  GC 54.1 – GC 54.2