O is for Observance, the shift from observing the return of the Sun to the return of the Son.

It was much later, in a gentile missionary context, that the Church established its observance and celebration of Christmas. Although the exact history of its origins is debated by the experts, we do know that Christmas has been celebrated in the city of Rome on December 25 ever since 336 AD, and that it soon became a universal, that is, "catholic," celebration. But why December 25?

As the Church moved out in mission into the world of the Roman Empire, it was greeted sometimes with tolerance and sometimes with persecution, but always with suspicion, especially by the upper and ruling classes. In 313 AD, however, things changed. Emperor Constantine became a Christian and thereby made it possible for the Church to "more legitimately" (that is, legally) spread the message of Christ. As the Church did this, it naturally confronted the popular religions of Rome, the celebrations of which were an integral part of the Roman culture. Being a very religious people, the Romans had some eighty religious festivals every year. One very popular celebration was the feast of the "Unconquered Sun-God," which the Roman emperor Aurelian established throughout the empire in 274 AD to honor the Syrian sun-god of Emesa. The day of celebration was set by Aurelian for December 25, the day they calculated for the winter solstice, the day when the sun-god began to show forth his power to lengthen the days and thereby bring forth the next year's life-saving harvest. The emperor's hope was also that the feast would help to unite and strengthen his vast empire over which the same sun shone.

In order to defend Christians against the attraction of this pagan feast, the Church in Rome established a festival of its own on the same day, December 25, the feast of the nativity of Christ -- Christmas. For the Church, the darkness that threatened everyone was not simply the darkness of night or the threat of perennial winter, but the darkness of sin and the winter of God's judgment upon it. The birth of Christ therefore was celebrated as the first light of God's power to save his people from the opposing powers of darkness through the death and resurrection of Jesus Christ. To highlight the truth of this festival, the Church pointed the faithful to the Scriptures themselves. Long ago, it was noted, the prophet Malachi had described the expected redeemer of the world as the "sun of righteousness"(Mal 4:2) and the prophet Isaiah had spoken of him as "your light." (Isa 60:1-2) In the New Testament, which had been pretty well established by then, both Matthew and Luke had already made the birth of Jesus an important part of the Church's telling of the Gospel. Moreover, Jesus Christ is recorded by St. John as describing himself as "the light of the world" (Jn 8:12), while in the Prologue to his Gospel, the text we read on Christmas Day, John boldly asserts that in Jesus Christ "the true light that enlightens everyone, [has now come] into the world." (1:9) And so, Christmas was celebrated.