It is a fact that Christianity is not a religion. It is a philosophy,” according to Bill O’Reilly. As part of his “war on Christmas” focus, the talk-show host faced off with the head of an Atheist organization in a recent interview. (For a different take, see this article from  the Washington Post.) According to his guest, government-supported celebrations of Christmas constitute the state’s privileging of one religion. If I understand him correctly (and I don’t take that for granted), Mr. O’Reilly counters the argument by suggesting that while particular denominations are “religions,” Christianity itself is not a religion but a philosophy. In fact, he takes this as a settled consensus. Oddly, he includes Judaism along with Methodism and Roman Catholicism as “religions,” although Judaism is arguably distinct from Christianity.

I confess that I am not a regular Fox News viewer and only catch Bill O’Reilly when friends shamelessly forward clips like these. Although the political aspect of the debate is important, my concern here is the religious aspect.

How far will some go to protect the vestiges of cultural Christianity in our increasingly secular society? Is this civil religion so deeply ingrained that we are willing to redefine the very nature and message of Christianity in the name of Christendom? Perhaps Mr. O’Reilly has given us that answer.

Could it be, ironically, that the atheist had a better idea about the nature of Christianity? To be sure, the danger of Christmas for him is mainly political, as its benefit seems to be for Mr. O’Reilly. But at least he gets that it’s about a specific religion and its central claim.

For many today, Christianity is indeed a philosophy—an ideology, a culture, and a set of ethical principles. It may come with different specifics, depending on whether it hails from the left or the right side of the aisle. However, if I may so bold, those who take this view should probably not celebrate Christmas at all.

Christianity is first and foremost an announcement that God our Creator is also our Redeemer; that “God so loved the world that he gave his only-begotten Son, so that whoever believes in him will never perish but have everlasting life” (Jn 3:16). This announcement is proclaimed in the gospel and sealed by baptism and the Lord’s Supper. It is explained in the ecumenical creeds, especially the Nicene, and shapes our common as well as private prayer, devotion, and life in the world. Christ did not come to be the world’s greatest philosopher or social reformer, but to “save his people from their sins” (Mat 1:21).

In the historic practice of many churches, the Sundays of Advent move from the prophecies to the nativity, culminating in the anticipation of Christ’s second advent. In this way, the point is underscored that the one whose gentle birth we celebrate is also the one who will return at the end of the age to judge the living and the dead and reign forever.

Even members of my extended family, many of them now unchurched, are not offended to celebrate Christmas. I think they should be. Christmas is a dangerous holiday. It’s not a question as to whether I think everyone has a right to celebrate Christmas in their own fashion. I won’t be pulling down decorations at the mall. However, I do question whether we know what we’re getting ourselves in to when we presume to celebrate Christ’s birth.

To be sure, we shouldn’t forget that Christmas, like every Lord’s Day, is first and foremost about announcing good news to all people: sins forgiven and the inheritance of everlasting life. The comfort of “God With Us,” rescuing us, the Light shining in the darkness: this is at the heart of our faith and our celebration of Christ’s birth. And yet, apart from meditation on his return in glory, the Good News become reduced to sentimental banality about mothers and babies; children being our future, roasting chestnuts and blinking lights.

When the Apostle Paul was invited to address the philosophers in Athens, he proclaimed this gospel. Already he had been busy in the synagogue as he “reasoned with them from the Scriptures, explaining and proving that the Christ had to suffer and rise from the dead.” “‘This Jesus I am proclaiming to you is the Christ,’ he said” (Acts 17:2-3). Then in the marketplace he reasoned with Greeks about Christ and his resurrection. That’s how he received the invitation to the big stage. He arrives at the climax of his argument: “For he [God] has set a day when he will judge the world with justice by the man he has appointed. He has given proof of this to all men by raising him from the dead.” (v 31).

The baby in the manger is God, who reigns over all together with the Father and the Holy Spirit. He infuriated the religious leaders by identifying them as outcasts, condemned to destruction, while welcoming sinners into his fellowship. He claimed equality with God the Father, provoking charges of blasphemy. He bore our guilt because there is no forgiveness apart from justice and every human being is under the curse of sin and death. He rose again on the third day for our justification and as the firstfruits of the new creation. He sent his Spirit to unite us to him for reconciliation and renewal. And one day he will return to judge the world, welcoming his elect into everlasting glory and banishing forever those who have not placed their trust in him.

The baby grew up. He is the conquering warrior of Isaiah 59 and before there can be an unending wedding feast in Revelation 19, there is the “wrath of the Lamb” in chapters 14-18. In those gruesome battle-scenes, the earthly city—represented collectively as “Babylon the Great”—is not confirmed in its cultural identity and civic pride, but is reduced to rubble. Instead of celebrating the shopping season with shareholders, the CEOs mourn that advent. The rulers of the earth beg that rocks fall on them to hide them from the wrath of Bethlehem’s child. If we do not recognize the holy child as the Lamb who died, was raised, and is coming again in judgment and everlasting blessing, then Christmas isn’t our holiday, but a dreadful anticipation of the final reckoning.

So Christmas is a wonderfully comforting holiday. In this era between his two advents, Christ is restraining Satan by his Word and Spirit, drawing sinners into the safety and joy of his banquet hall. Yet it is also a dangerous holiday, especially for those who defend it only by using it, “having a form of godliness but denying its power” (2 Tim 3:5-7). Are we really sure that we want to celebrate this birth? Are we glad when pass by the nativity scene on the city lawn, defended as an American “philosophy”?

Better to gather together in churches—even under conditions of persecution around the world—where (one hopes) Christ is proclaimed as the Judge and the Justifier of the ungodly this Christmas. And there, with faith in the holy Lamb, we can hear the angel say also to us, “Do not be afraid. I bring you good news of great joy that will be for all the people. Today in the town of David a Savior has been born to you; he is Christ the Lord” (Lk 2:10).